zeroinstall/injector/solver.py

   1 """
   2 Chooses a set of components to make a running program.
   3 """
   4
   5 # Copyright (C) 2009, Thomas Leonard
   6 # See the README file for details, or visit http://0install.net.
   7
   8 from zeroinstall import _
   9 import locale
  10 from logging import debug, warn, info
  11
  12 from zeroinstall.injector.reader import MissingLocalFeed
  13 from zeroinstall.injector import model, sat, selections, arch
  14
  15 class CommandInfo:
  16         def __init__(self, name, command, impl, arch):
  17                 self.name = name
  18                 self.command = command
  19                 self.impl = impl
  20                 self.arch = arch
  21
  22         def __repr__(self):
  23                 name = "%s_%s_%s_%s" % (self.impl.feed.get_name(), self.impl.get_version(), self.impl.arch, self.name)
  24                 return name.replace('-', '_').replace('.', '_')
  25
  26 class ImplInfo:
  27         is_dummy = False
  28
  29         def __init__(self, iface, impl, arch, dummy = False):
  30                 self.iface = iface
  31                 self.impl = impl
  32                 self.arch = arch
  33                 if dummy:
  34                         self.is_dummy = True
  35
  36         def __repr__(self):
  37                 name = "%s_%s_%s" % (self.impl.feed.get_name(), self.impl.get_version(), self.impl.arch)
  38                 return name.replace('-', '_').replace('.', '_')
  39
  40 class _DummyImpl(object):
  41         requires = []
  42         version = None
  43         arch = None
  44         commands = {}
  45
  46         def __repr__(self):
  47                 return "dummy"
  48
  49         feed = property(lambda self: self)
  50
  51         def get_version(self):
  52                 return "dummy"
  53
  54         def get_name(self):
  55                 return "dummy"
  56
  57 class _ForceImpl(model.Restriction):
  58         """Used by L{SATSolver.justify_decision}."""
  59
  60         def __init__(self, impl_id):
  61                 self.impl_id = impl_id
  62
  63         def meets_restriction(self, impl):
  64                 return impl.id == self.impl_id
  65
  66 class Solver(object):
  67         """Chooses a set of implementations to satisfy the requirements of a program and its user.
  68         Typical use:
  69          1. Create a Solver object and configure it
  70          2. Call L{solve}.
  71          3. If any of the returned feeds_used are stale or missing, you may like to start downloading them
  72          4. If it is 'ready' then you can download and run the chosen versions.
  73         @ivar selections: the chosen implementation of each interface
  74         @type selections: L{selections.Selections}
  75         @ivar requires: the selected dependencies for each chosen version
  76         @type requires: {L{model.Interface}: [L{model.Dependency}]}
  77         @ivar feeds_used: the feeds which contributed to the choice in L{selections}
  78         @type feeds_used: set(str)
  79         @ivar record_details: whether to record information about unselected implementations
  80         @type record_details: {L{Interface}: [(L{Implementation}, str)]}
  81         @ivar details: extra information, if record_details mode was used
  82         @type details: {str: [(Implementation, comment)]}
  83         """
  84         __slots__ = ['selections', 'requires', 'feeds_used', 'details', 'record_details', 'ready']
  85
  86         def __init__(self):
  87                 self.selections = self.requires = self.feeds_used = self.details = None
  88                 self.record_details = False
  89                 self.ready = False
  90
  91         def solve_for(self, requirements):
  92                 """Solve for given requirements.
  93                 @param requirements: the interface, architecture and command to solve for
  94                 @type requirements: L{requirements.Requirements}
  95                 @postcondition: self.ready, self.selections and self.feeds_used are updated
  96                 @since: 1.8"""
  97                 return self.solve(requirements.interface_uri, self.get_arch_for(requirements), requirements.command)
  98
  99         def solve(self, root_interface, root_arch, command_name = 'run'):
 100                 """Get the best implementation of root_interface and all of its dependencies.
 101                 @param root_interface: the URI of the program to be solved
 102                 @type root_interface: str
 103                 @param root_arch: the desired target architecture
 104                 @type root_arch: L{arch.Architecture}
 105                 @param command_name: which <command> element to select
 106                 @type command_name: str | None
 107                 @postcondition: self.ready, self.selections and self.feeds_used are updated"""
 108                 raise NotImplementedError("Abstract")
 109
 110         def get_arch_for(self, requirements, interface = None):
 111                 """Return the Architecture we would use when solving for this interface.
 112                 Normally, this architecture is constructed from the OS and CPU type in the requirements,
 113                 using the host platform's settings if these are not given.
 114                 If interface is the root, then we wrap this in a SourceArchitecture if looking
 115                 for source code and (for backwards compatibility) we enable use="testing" dependencies
 116                 if the command is "test".
 117                 @param requirements: the overall requirements for the solve
 118                 @type requirements: L{requirements.Requirements}
 119                 @param interface: the interface of interest
 120                 @type interface: L{model.Interface}
 121                 @return: the architecture that would be used
 122                 @rtype: L{architecture.Architecture}
 123                 @since: 1.9"""
 124                 root_arch = arch.get_architecture(requirements.os, requirements.cpu)
 125                 if interface is None or interface.uri == requirements.interface_uri:
 126                         if requirements.source:
 127                                 root_arch = arch.SourceArchitecture(root_arch)
 128                         if requirements.command == 'test':
 129                                 # This is for old feeds that have use='testing' instead of the newer
 130                                 # 'test' command for giving test-only dependencies.
 131                                 root_arch = arch.Architecture(root_arch.os_ranks, root_arch.machine_ranks)
 132                                 root_arch.use = frozenset([None, "testing"])
 133                         return root_arch
 134                 # Assume we use the same arch for all descendants
 135                 return root_arch.child_arch
 136
 137 class SATSolver(Solver):
 138         """Converts the problem to a set of pseudo-boolean constraints and uses a PB solver to solve them.
 139         @ivar langs: the preferred languages (e.g. ["es_ES", "en"]). Initialised to the current locale.
 140         @type langs: str"""
 141
 142         __slots__ = ['_failure_reason', 'config', 'extra_restrictions', '_lang_ranks', '_langs']
 143
 144         @property
 145         def iface_cache(self):
 146                 return self.config.iface_cache  # (deprecated; used by 0compile)
 147
 148         def __init__(self, config, extra_restrictions = None):
 149                 """
 150                 @param config: policy preferences (e.g. stability), the iface_cache and the stores to use
 151                 @type config: L{policy.Config}
 152                 @param extra_restrictions: extra restrictions on the chosen implementations
 153                 @type extra_restrictions: {L{model.Interface}: [L{model.Restriction}]}
 154                 """
 155                 Solver.__init__(self)
 156                 assert not isinstance(config, str), "API change!"
 157                 self.config = config
 158                 self.extra_restrictions = extra_restrictions or {}
 159
 160                 # By default, prefer the current locale's language first and English second
 161                 self.langs = [locale.getlocale()[0] or 'en', 'en']
 162
 163         def set_langs(self, langs):
 164                 """Set the preferred languages.
 165                 @param langs: languages (and regions), first choice first
 166                 @type langs: [str]
 167                 """
 168                 # _lang_ranks is a map from locale string to score (higher is better)
 169                 _lang_ranks = {}
 170                 score = 0
 171                 i = len(langs)
 172                 # (is there are duplicates, the first occurance takes precedence)
 173                 while i > 0:
 174                         i -= 1
 175                         lang = langs[i].replace('_', '-')
 176                         _lang_ranks[lang.split('-')[0]] = score
 177                         _lang_ranks[lang] = score + 1
 178                         score += 2
 179                 self._langs = langs
 180                 self._lang_ranks = _lang_ranks
 181
 182         langs = property(lambda self: self._langs, set_langs)
 183
 184         def get_rating(self, interface, impl, arch):
 185                 impl_langs = (impl.langs or 'en').split()
 186                 my_langs = self._lang_ranks
 187
 188                 stores = self.config.stores
 189                 is_available = impl.is_available(stores)
 190
 191                 # Stability
 192                 stab_policy = interface.stability_policy
 193                 if not stab_policy:
 194                         if self.config.help_with_testing: stab_policy = model.testing
 195                         else: stab_policy = model.stable
 196
 197                 stability = impl.get_stability()
 198                 if stability >= stab_policy:
 199                         stability_limited = model.preferred
 200                 else:
 201                         stability_limited = stability
 202
 203                 # Note: this list must match _ranking_component_reason above
 204                 return [
 205                         # Languages we understand come first
 206                         max(my_langs.get(l.split('-')[0], -1) for l in impl_langs),
 207
 208                         # Preferred versions come first
 209                         stability == model.preferred,
 210
 211                         # Prefer available implementations next if we have limited network access
 212                         self.config.network_use != model.network_full and is_available,
 213
 214                         # Packages that require admin access to install come last
 215                         not impl.requires_root_install,
 216
 217                         # Prefer more stable versions, but treat everything over stab_policy the same
 218                         # (so we prefer stable over testing if the policy is to prefer "stable", otherwise
 219                         # we don't care)
 220                         stability_limited,
 221
 222                         # Newer versions come before older ones (ignoring modifiers)
 223                         impl.version[0],
 224
 225                         # Prefer native packages if the main part of the versions are the same
 226                         impl.id.startswith('package:'),
 227
 228                         # Full version compare (after package check, since comparing modifiers between native and non-native
 229                         # packages doesn't make sense).
 230                         impl.version,
 231
 232                         # Get best OS
 233                         -arch.os_ranks.get(impl.os, 999),
 234
 235                         # Get best machine
 236                         -arch.machine_ranks.get(impl.machine, 999),
 237
 238                         # Slightly prefer languages specialised to our country
 239                         # (we know a and b have the same base language at this point)
 240                         max(my_langs.get(l, -1) for l in impl_langs),
 241
 242                         # Slightly prefer cached versions
 243                         is_available,
 244
 245                         # Order by ID so the order isn't random
 246                         impl.id
 247                 ]
 248
 249         def solve(self, root_interface, root_arch, command_name = 'run', closest_match = False):
 250                 # closest_match is used internally. It adds a lowest-ranked
 251                 # by valid implementation to every interface, so we can always
 252                 # select something. Useful for diagnostics.
 253
 254                 # The basic plan is this:
 255                 # 1. Scan the root interface and all dependencies recursively, building up a SAT problem.
 256                 # 2. Solve the SAT problem. Whenever there are multiple options, try the most preferred one first.
 257                 # 3. Create a Selections object from the results.
 258                 #
 259                 # All three involve recursively walking the tree in a similar way:
 260                 # 1) we follow every dependency of every implementation (order not important)
 261                 # 2) we follow every dependency of every selected implementation (better versions first)
 262                 # 3) we follow every dependency of every selected implementation (order doesn't matter)
 263                 #
 264                 # In all cases, a dependency may be on an <implementation> or on a specific <command>.
 265
 266                 # TODO: We need some way to figure out which feeds to include.
 267                 # Currently, we include any feed referenced from anywhere but
 268                 # this is probably too much. We could insert a dummy optimial
 269                 # implementation in stale/uncached feeds and see whether it
 270                 # selects that.
 271                 iface_cache = self.config.iface_cache
 272
 273                 problem = sat.SATProblem()
 274
 275                 impl_to_var = {}        # Impl -> sat var
 276                 self.feeds_used = set()
 277                 self.requires = {}
 278                 self.ready = False
 279                 self.details = self.record_details and {}
 280
 281                 self.selections = None
 282                 self._failure_reason = None
 283
 284                 ifaces_processed = set()
 285
 286                 machine_groups = arch.machine_groups
 287                 impls_for_machine_group = {0 : []}              # Machine group (e.g. "64") to [impl] in that group
 288                 for machine_group in machine_groups.values():
 289                         impls_for_machine_group[machine_group] = []
 290
 291                 impls_for_iface = {}    # Iface -> [impl]
 292
 293                 group_clause_for = {}   # Iface URI -> AtMostOneClause | bool
 294                 group_clause_for_command = {}   # (Iface URI, command name) -> AtMostOneClause | bool
 295
 296                 # Return the dependencies of impl that we should consider.
 297                 # Skips dependencies if the use flag isn't what we need.
 298                 # (note: impl may also be a model.Command)
 299                 def deps_in_use(impl, arch):
 300                         for dep in impl.requires:
 301                                 use = dep.metadata.get("use", None)
 302                                 if use not in arch.use:
 303                                         continue
 304                                 yield dep
 305
 306                 # Must have already done add_iface on dependency.interface.
 307                 # If dependency is essential:
 308                 #   Add a clause so that if requiring_impl_var is True then an implementation
 309                 #   matching 'dependency' must also be selected.
 310                 # If dependency is optional:
 311                 #   Require that no incompatible version is selected.
 312                 # This ignores any 'command' required. Handle that separately.
 313                 def find_dependency_candidates(requiring_impl_var, dependency):
 314                         def meets_restrictions(candidate):
 315                                 for r in dependency.restrictions:
 316                                         if not r.meets_restriction(candidate):
 317                                                 #warn("%s rejected due to %s", candidate.get_version(), r)
 318                                                 return False
 319                                 return True
 320
 321                         essential = dependency.importance == model.Dependency.Essential
 322
 323                         dep_iface = iface_cache.get_interface(dependency.interface)
 324                         dep_union = [sat.neg(requiring_impl_var)]       # Either requiring_impl_var is False, or ...
 325                         for candidate in impls_for_iface[dep_iface]:
 326                                 if (candidate.__class__ is _DummyImpl) or meets_restrictions(candidate):
 327                                         if essential:
 328                                                 c_var = impl_to_var.get(candidate, None)
 329                                                 if c_var is not None:
 330                                                         dep_union.append(c_var)
 331                                                 # else we filtered that version out, so ignore it
 332                                 else:
 333                                         # Candidate doesn't meet our requirements
 334                                         # If the dependency is optional add a rule to make sure we don't
 335                                         # select this candidate.
 336                                         # (for essential dependencies this isn't necessary because we must
 337                                         # select a good version and we can't select two)
 338                                         if not essential:
 339                                                 c_var = impl_to_var.get(candidate, None)
 340                                                 if c_var is not None:
 341                                                         problem.add_clause(dep_union + [sat.neg(c_var)])
 342                                                 # else we filtered that version out, so ignore it
 343
 344                         if essential:
 345                                 problem.add_clause(dep_union)
 346
 347                 def is_unusable(impl, restrictions, arch):
 348                         """@return: whether this implementation is unusable.
 349                         @rtype: bool"""
 350                         return get_unusable_reason(impl, restrictions, arch) != None
 351
 352                 def get_unusable_reason(impl, restrictions, arch):
 353                         """
 354                         @param impl: Implementation to test.
 355                         @type restrictions: [L{model.Restriction}]
 356                         @return: The reason why this impl is unusable, or None if it's OK.
 357                         @rtype: str
 358                         @note: The restrictions are for the interface being requested, not the feed
 359                         of the implementation; they may be different when feeds are being used."""
 360                         for r in restrictions:
 361                                 if not r.meets_restriction(impl):
 362                                         return _("Incompatible with another selected implementation")
 363                         stability = impl.get_stability()
 364                         if stability <= model.buggy:
 365                                 return stability.name
 366                         if (self.config.network_use == model.network_offline or not impl.download_sources) and not impl.is_available(self.config.stores):
 367                                 if not impl.download_sources:
 368                                         return _("No retrieval methods")
 369                                 return _("Not cached and we are off-line")
 370                         if impl.os not in arch.os_ranks:
 371                                 return _("Unsupported OS")
 372                         if impl.machine not in arch.machine_ranks:
 373                                 if impl.machine == 'src':
 374                                         return _("Source code")
 375                                 elif 'src' in arch.machine_ranks:
 376                                         return _("Not source code")
 377                                 return _("Unsupported machine type")
 378                         return None
 379
 380                 def usable_feeds(iface, arch):
 381                         """Return all feeds for iface that support arch.
 382                         @rtype: generator(ZeroInstallFeed)"""
 383                         yield iface.uri
 384
 385                         for f in iface_cache.get_feed_imports(iface):
 386                                 # Note: when searching for src, None is not in machine_ranks
 387                                 if f.os in arch.os_ranks and \
 388                                    (f.machine is None or f.machine in arch.machine_ranks):
 389                                         yield f.uri
 390                                 else:
 391                                         debug(_("Skipping '%(feed)s'; unsupported architecture %(os)s-%(machine)s"),
 392                                                 {'feed': f, 'os': f.os, 'machine': f.machine})
 393
 394                 # If requiring_var is True then all of requirer's dependencies must be satisfied.
 395                 # requirer can be a <command> or an <implementation>
 396                 def process_dependencies(requiring_var, requirer, arch):
 397                         for d in deps_in_use(requirer, arch):
 398                                 debug(_("Considering command dependency %s"), d)
 399
 400                                 add_iface(d.interface, arch.child_arch)
 401
 402                                 for c in d.get_required_commands():
 403                                         # We depend on a specific command within the implementation.
 404                                         command_vars = add_command_iface(d.interface, arch.child_arch, c)
 405
 406                                         # If the parent command/impl is chosen, one of the candidate commands
 407                                         # must be too. If there aren't any, then this command is unselectable.
 408                                         problem.add_clause([sat.neg(requiring_var)] + command_vars)
 409
 410                                 # Must choose one version of d if impl is selected
 411                                 find_dependency_candidates(requiring_var, d)
 412
 413                 def add_iface(uri, arch):
 414                         """Name implementations from feed and assert that only one can be selected."""
 415                         if uri in ifaces_processed: return
 416                         ifaces_processed.add(uri)
 417
 418                         iface = iface_cache.get_interface(uri)
 419
 420                         impls = []
 421                         for f in usable_feeds(iface, arch):
 422                                 self.feeds_used.add(f)
 423                                 debug(_("Processing feed %s"), f)
 424
 425                                 try:
 426                                         feed = iface_cache.get_feed(f)
 427                                         if feed is None: continue
 428                                         #if feed.name and iface.uri != feed.url and iface.uri not in feed.feed_for:
 429                                         #       info(_("Missing <feed-for> for '%(uri)s' in '%(feed)s'"), {'uri': iface.uri, 'feed': f})
 430
 431                                         if feed.implementations:
 432                                                 impls.extend(feed.implementations.values())
 433
 434                                         distro_feed_url = feed.get_distro_feed()
 435                                         if distro_feed_url:
 436                                                 self.feeds_used.add(distro_feed_url)
 437                                                 distro_feed = iface_cache.get_feed(distro_feed_url)
 438                                                 if distro_feed.implementations:
 439                                                         impls.extend(distro_feed.implementations.values())
 440                                 except MissingLocalFeed as ex:
 441                                         warn(_("Missing local feed; if it's no longer required, remove it with:") +
 442                                                         '\n0install remove-feed ' + iface.uri + ' ' + f,
 443                                                 {'feed': f, 'interface': iface, 'exception': ex})
 444                                 except Exception as ex:
 445                                         warn(_("Failed to load feed %(feed)s for %(interface)s: %(exception)s"), {'feed': f, 'interface': iface, 'exception': ex})
 446                                         #raise
 447
 448                         impls.sort(key = lambda impl: self.get_rating(iface, impl, arch), reverse = True)
 449
 450                         impls_for_iface[iface] = filtered_impls = []
 451
 452                         my_extra_restrictions = self.extra_restrictions.get(iface, [])
 453
 454                         if self.record_details:
 455                                 self.details[iface] = [(impl, get_unusable_reason(impl, my_extra_restrictions, arch)) for impl in impls]
 456
 457                         var_names = []
 458                         for impl in impls:
 459                                 if is_unusable(impl, my_extra_restrictions, arch):
 460                                         continue
 461
 462                                 filtered_impls.append(impl)
 463
 464                                 assert impl not in impl_to_var
 465                                 v = problem.add_variable(ImplInfo(iface, impl, arch))
 466                                 impl_to_var[impl] = v
 467                                 var_names.append(v)
 468
 469                                 if impl.machine and impl.machine != 'src':
 470                                         impls_for_machine_group[machine_groups.get(impl.machine, 0)].append(v)
 471
 472                                 process_dependencies(v, impl, arch)
 473
 474                         if closest_match:
 475                                 dummy_impl = _DummyImpl()
 476                                 dummy_var = problem.add_variable(ImplInfo(iface, dummy_impl, arch, dummy = True))
 477                                 var_names.append(dummy_var)
 478                                 impl_to_var[dummy_impl] = dummy_var
 479                                 filtered_impls.append(dummy_impl)
 480
 481                         # Only one implementation of this interface can be selected
 482                         if uri == root_interface:
 483                                 if var_names:
 484                                         clause = problem.at_most_one(var_names)
 485                                         problem.add_clause(var_names)   # at least one
 486                                 else:
 487                                         problem.impossible()
 488                                         clause = False
 489                         elif var_names:
 490                                 clause = problem.at_most_one(var_names)
 491                         else:
 492                                 # Don't need to add to group_clause_for because we should
 493                                 # never get a possible selection involving this.
 494                                 return
 495
 496                         assert clause is not True
 497                         assert clause is not None
 498                         if clause is not False:
 499                                 group_clause_for[uri] = clause
 500
 501                 def add_command_iface(uri, arch, command_name):
 502                         """Add every <command> in interface 'uri' with this name.
 503                         Each one depends on the corresponding implementation and only
 504                         one can be selected. If closest_match is on, include a dummy
 505                         command that can always be selected."""
 506
 507                         # Check whether we've already processed this (interface,command) pair
 508                         existing = group_clause_for_command.get((uri, command_name), None)
 509                         if existing is not None:
 510                                 return existing.lits
 511
 512                         # First ensure that the interface itself has been processed
 513                         # We'll reuse the ordering of the implementations to order
 514                         # the commands too.
 515                         add_iface(uri, arch)
 516
 517                         iface = iface_cache.get_interface(uri)
 518                         filtered_impls = impls_for_iface[iface]
 519
 520                         var_names = []
 521                         for impl in filtered_impls:
 522                                 command = impl.commands.get(command_name, None)
 523                                 if not command:
 524                                         if not isinstance(impl, _DummyImpl):
 525                                                 # Mark implementation as unselectable
 526                                                 problem.add_clause([sat.neg(impl_to_var[impl])])
 527                                         continue
 528
 529                                 # We have a candidate <command>. Require that if it's selected
 530                                 # then we select the corresponding <implementation> too.
 531                                 command_var = problem.add_variable(CommandInfo(command_name, command, impl, arch))
 532                                 problem.add_clause([impl_to_var[impl], sat.neg(command_var)])
 533
 534                                 var_names.append(command_var)
 535
 536                                 process_dependencies(command_var, command, arch)
 537
 538                         # Tell the user why we couldn't use this version
 539                         if self.record_details:
 540                                 def new_reason(impl, old_reason):
 541                                         if command_name in impl.commands:
 542                                                 return old_reason
 543                                         return old_reason or (_('No %s command') % command_name)
 544                                 self.details[iface] = [(impl, new_reason(impl, reason)) for (impl, reason) in self.details[iface]]
 545
 546                         if closest_match:
 547                                 dummy_command = problem.add_variable(None)
 548                                 var_names.append(dummy_command)
 549
 550                         if var_names:
 551                                 # Can't select more than one of them.
 552                                 assert (uri, command_name) not in group_clause_for_command
 553                                 group_clause_for_command[(uri, command_name)] = problem.at_most_one(var_names)
 554
 555                         return var_names
 556
 557                 if command_name is None:
 558                         add_iface(root_interface, root_arch)
 559                 else:
 560                         commands = add_command_iface(root_interface, root_arch, command_name)
 561                         if len(commands) > int(closest_match):
 562                                 # (we have at least one non-dummy command)
 563                                 problem.add_clause(commands)            # At least one
 564                         else:
 565                                 # (note: might be because we haven't cached it yet)
 566                                 info("No %s <command> in %s", command_name, root_interface)
 567
 568                                 impls = impls_for_iface[iface_cache.get_interface(root_interface)]
 569                                 if impls == [] or (len(impls) == 1 and isinstance(impls[0], _DummyImpl)):
 570                                         # There were no candidates at all.
 571                                         if self.config.network_use == model.network_offline:
 572                                                 self._failure_reason = _("Interface '%s' has no usable implementations in the cache (and 0install is in off-line mode)") % root_interface
 573                                         else:
 574                                                 self._failure_reason = _("Interface '%s' has no usable implementations") % root_interface
 575                                 else:
 576                                         # We had some candidates implementations, but none for the command we need
 577                                         self._failure_reason = _("Interface '%s' cannot be executed directly; it is just a library "
 578                                                     "to be used by other programs (or missing '%s' command)") % (root_interface, command_name)
 579
 580                                 problem.impossible()
 581
 582                 # Require m<group> to be true if we select an implementation in that group
 583                 m_groups = []
 584                 for machine_group, impls in impls_for_machine_group.items():
 585                         m_group = 'm%d' % machine_group
 586                         group_var = problem.add_variable(m_group)
 587                         if impls:
 588                                 for impl in impls:
 589                                         problem.add_clause([group_var, sat.neg(impl)])
 590                         m_groups.append(group_var)
 591                 if m_groups:
 592                         m_groups_clause = problem.at_most_one(m_groups)
 593                 else:
 594                         m_groups_clause = None
 595
 596                 def decide():
 597                         """Recurse through the current selections until we get to an interface with
 598                         no chosen version, then tell the solver to try the best version from that."""
 599
 600                         def find_undecided_dep(impl_or_command, arch):
 601                                 # Check for undecided dependencies of impl_or_command
 602                                 for dep in deps_in_use(impl_or_command, arch):
 603                                         for c in dep.get_required_commands():
 604                                                 dep_lit = find_undecided_command(dep.interface, c)
 605                                                 if dep_lit is not None:
 606                                                         return dep_lit
 607                                         dep_lit = find_undecided(dep.interface)
 608                                         if dep_lit is not None:
 609                                                 return dep_lit
 610                                 return None
 611
 612                         seen = set()
 613                         def find_undecided(uri):
 614                                 if uri in seen:
 615                                         return  # Break cycles
 616                                 seen.add(uri)
 617
 618                                 group = group_clause_for.get(uri, None)
 619
 620                                 if group is None:
 621                                         # (can be None if the selected impl has an optional dependency on
 622                                         # a feed with no implementations)
 623                                         return
 624
 625                                 #print "Group for %s = %s" % (uri, group)
 626                                 lit = group.current
 627                                 if lit is None:
 628                                         return group.best_undecided()
 629                                 # else there was only one choice anyway
 630
 631                                 # Check for undecided dependencies
 632                                 lit_info = problem.get_varinfo_for_lit(lit).obj
 633                                 return find_undecided_dep(lit_info.impl, lit_info.arch)
 634
 635                         def find_undecided_command(uri, name):
 636                                 if name is None: return find_undecided(uri)
 637
 638                                 group = group_clause_for_command[(uri, name)]
 639                                 lit = group.current
 640                                 if lit is None:
 641                                         return group.best_undecided()
 642                                 # else we've already chosen which <command> to use
 643
 644                                 # Check for undecided command-specific dependencies, and then for
 645                                 # implementation dependencies.
 646                                 lit_info = problem.get_varinfo_for_lit(lit).obj
 647                                 if lit_info is None:
 648                                         assert closest_match
 649                                         return None     # (a dummy command added for better diagnostics; has no dependencies)
 650                                 return find_undecided_dep(lit_info.command, lit_info.arch) or \
 651                                        find_undecided_dep(lit_info.impl, lit_info.arch)
 652
 653                         best = find_undecided_command(root_interface, command_name)
 654                         if best is not None:
 655                                 return best
 656
 657                         # If we're chosen everything we need, we can probably
 658                         # set everything else to False.
 659                         for group in list(group_clause_for.values()) + list(group_clause_for_command.values()) + [m_groups_clause]:
 660                                 if group.current is None:
 661                                         best = group.best_undecided()
 662                                         if best is not None:
 663                                                 return sat.neg(best)
 664
 665                         return None                     # Failed to find any valid combination
 666
 667                 ready = problem.run_solver(decide) is True
 668
 669                 if not ready and not closest_match:
 670                         # We failed while trying to do a real solve.
 671                         # Try a closest match solve to get a better
 672                         # error report for the user.
 673                         self.solve(root_interface, root_arch, command_name = command_name, closest_match = True)
 674                 else:
 675                         self.ready = ready and not closest_match
 676                         self.selections = selections.Selections(None)
 677                         self.selections.interface = root_interface
 678
 679                         sels = self.selections.selections
 680
 681                         commands_needed = []
 682
 683                         # Populate sels with the selected implementations.
 684                         # Also, note down all the commands we need.
 685                         for uri, group in group_clause_for.items():
 686                                 if group.current is not None:
 687                                         lit_info = problem.get_varinfo_for_lit(group.current).obj
 688                                         if lit_info.is_dummy:
 689                                                 sels[lit_info.iface.uri] = None
 690                                         else:
 691                                                 # We selected an implementation for interface 'uri'
 692                                                 impl = lit_info.impl
 693
 694                                                 for b in impl.bindings:
 695                                                         c = b.command
 696                                                         if c is not None:
 697                                                                 commands.append((uri, c))
 698
 699                                                 deps = self.requires[lit_info.iface] = []
 700                                                 for dep in deps_in_use(lit_info.impl, lit_info.arch):
 701                                                         deps.append(dep)
 702                                                         for c in dep.get_required_commands():
 703                                                                 commands_needed.append((dep.interface, c))
 704
 705                                                 sels[lit_info.iface.uri] = selections.ImplSelection(lit_info.iface.uri, impl, deps)
 706
 707                         # Now all all the commands in too.
 708                         def add_command(iface, name):
 709                                 sel = sels.get(iface, None)
 710                                 if sel:
 711                                         command = sel.impl.commands[name]
 712                                         if name in sel._used_commands:
 713                                                 return  # Already added
 714                                         sel._used_commands.add(name)
 715
 716                                         for dep in command.requires:
 717                                                 for dep_command_name in dep.get_required_commands():
 718                                                         add_command(dep.interface, dep_command_name)
 719
 720                                         # A <command> can depend on another <command> in the same interface
 721                                         # (e.g. the tests depending on the main program)
 722                                         for b in command.bindings:
 723                                                 c = b.command
 724                                                 if c is not None:
 725                                                         add_command(iface, c)
 726
 727                         for iface, command in commands_needed:
 728                                 add_command(iface, command)
 729
 730                         if command_name is not None:
 731                                 self.selections.command = command_name
 732                                 add_command(root_interface, command_name)
 733
 734         def get_failure_reason(self):
 735                 """Return an exception explaining why the solve failed."""
 736                 assert not self.ready
 737
 738                 if self._failure_reason:
 739                         return model.SafeException(self._failure_reason)
 740
 741                 return model.SafeException(_("Can't find all required implementations:") + '\n' +
 742                                 '\n'.join(["- %s -> %s" % (iface, self.selections[iface])
 743                                            for iface  in self.selections]))
 744
 745         def justify_decision(self, requirements, iface, impl):
 746                 """Run a solve with impl_id forced to be selected, and explain why it wasn't (or was)
 747                 selected in the normal case."""
 748                 assert isinstance(iface, model.Interface), iface
 749
 750                 restrictions = self.extra_restrictions.copy()
 751                 restrictions[iface] = restrictions.get(iface, []) + [_ForceImpl(impl.id)]
 752                 s = SATSolver(self.config, restrictions)
 753                 s.record_details = True
 754                 s.solve_for(requirements)
 755
 756                 wanted = "{iface} {version}".format(iface = iface.get_name(), version = impl.get_version())
 757
 758                 # Could a selection involving impl even be valid?
 759                 if not s.ready or iface.uri not in s.selections.selections:
 760                         reasons = s.details.get(iface, [])
 761                         for (rid, rstr) in reasons:
 762                                 if rid.id == impl.id and rstr is not None:
 763                                         return _("{wanted} cannot be used (regardless of other components): {reason}").format(
 764                                                         wanted = wanted,
 765                                                         reason = rstr)
 766
 767                         if not s.ready:
 768                                 return _("There is no possible selection using {wanted}.\n{reason}").format(
 769                                         wanted = wanted,
 770                                         reason = s.get_failure_reason())
 771
 772                 actual_selection = self.selections.get(iface, None)
 773                 if actual_selection is not None:
 774                         # Was impl actually selected anyway?
 775                         if actual_selection.id == impl.id:
 776                                 return _("{wanted} was selected as the preferred version.").format(wanted = wanted)
 777
 778                         # Was impl ranked below the selected version?
 779                         iface_arch = arch.get_architecture(requirements.os, requirements.cpu)
 780                         if requirements.source and iface.uri == requirements.interface_uri:
 781                                 iface_arch = arch.SourceArchitecture(iface_arch)
 782                         wanted_rating = self.get_rating(iface, impl, arch)
 783                         selected_rating = self.get_rating(iface, actual_selection, arch)
 784
 785                         if wanted_rating < selected_rating:
 786                                 _ranking_component_reason = [
 787                                         _("natural languages we understand are preferred"),
 788                                         _("preferred versions come first"),
 789                                         _("locally-available versions are preferred when network use is limited"),
 790                                         _("packages that don't require admin access to install are preferred"),
 791                                         _("more stable versions preferred"),
 792                                         _("newer versions are preferred"),
 793                                         _("native packages are preferred"),
 794                                         _("newer versions are preferred"),
 795                                         _("better OS match"),
 796                                         _("better CPU match"),
 797                                         _("better locale match"),
 798                                         _("is locally available"),
 799                                         _("better ID (tie-breaker)"),
 800                                 ]
 801
 802                                 actual = actual_selection.get_version()
 803                                 if impl.get_version() == actual:
 804                                         def detail(i):
 805                                                 if len(i.id) < 18:
 806                                                         return " (" + i.id + ")"
 807                                                 else:
 808                                                         return " (" + i.id[:16] + "...)"
 809
 810                                         wanted += detail(impl)
 811                                         actual += detail(actual_selection)
 812
 813                                 for i in range(len(wanted_rating)):
 814                                         if wanted_rating[i] < selected_rating[i]:
 815                                                 return _("{wanted} is ranked lower than {actual}: {why}").format(
 816                                                                 wanted = wanted,
 817                                                                 actual = actual,
 818                                                                 why = _ranking_component_reason[i])
 819
 820                 used_impl = iface.uri in s.selections.selections
 821
 822                 # Impl is selectable and ranked higher than the selected version. Selecting it would cause
 823                 # a problem elsewhere.
 824                 changes = []
 825                 for old_iface, old_sel in self.selections.selections.items():
 826                         if old_iface == iface.uri and used_impl: continue
 827                         new_sel = s.selections.selections.get(old_iface, None)
 828                         if new_sel is None:
 829                                 changes.append(_("{interface}: no longer used").format(interface = old_iface))
 830                         elif old_sel.version != new_sel.version:
 831                                 changes.append(_("{interface}: {old} to {new}").format(interface = old_iface, old = old_sel.version, new = new_sel.version))
 832                         elif old_sel.id != new_sel.id:
 833                                 changes.append(_("{interface}: {old} to {new}").format(interface = old_iface, old = old_sel.id, new = new_sel.id))
 834
 835                 if changes:
 836                         changes_text = '\n\n' + _('The changes would be:') + '\n\n' + '\n'.join(changes)
 837                 else:
 838                         changes_text = ''
 839
 840                 if used_impl:
 841                         return _("{wanted} is selectable, but using it would produce a less optimal solution overall.").format(wanted = wanted) + changes_text
 842                 else:
 843                         return _("If {wanted} were the only option, the best available solution wouldn't use it.").format(wanted = wanted) + changes_text
 844
 845 DefaultSolver = SATSolver