version 0.76_01

[sepia.git] / sepia.texi

\input texinfo   @c -*-texinfo-*-
@c %**start of header
@setfilename sepia.info
@settitle Simple Emacs Perl Integration
@dircategory Emacs
@direntry
* Sepia: (sepia).    Simple Emacs Perl Integration.
@end direntry
@c %**end of header

@titlepage
@title Sepia: Simple Emacs Perl Integration
@author Sean O'Rourke
@end titlepage

@macro kbinding{key,cmd}
@item \key\ `\cmd\'
@kindex \key\
@end macro

@macro fitem{name}
@item \name\
@findex \name\
@end macro

@macro xxx{stuff}
@b{XXX: \stuff\}
@end macro

@node Top, Introduction, (dir), (dir)

@ifinfo
@top SEPIA
@end ifinfo

Sepia is a set of Perl development tools for Emacs supporting code
navigation and interactive evaluation.

@menu
* Introduction::                
* Editing::                     
* Interactive Perl::            
* Customization::               
* Internals::                   
* Credits::                     
* Function Index::              
@end menu

@c ============================================================
@node Introduction, Editing, Top, Top
@chapter Introduction

Sepia is a set of tools for Perl development in Emacs.  Its goal is to
extend CPerl mode with two contributions: fast code navigation and
interactive development.  It is inspired by Emacs' current support for a
number of other languages, including Lisp, Python, and Emacs Lisp.

@menu
* Getting Started::             
* Philosophy::                  
@end menu

@node Getting Started, Philosophy, Introduction, Introduction
@section Getting Started

To install Sepia, its Emacs Lisp files must be in Emacs'
@code{load-path}, and the @file{lib} directory must be in Perl's
@code{@@INC}.  Assuming that Sepia has been unpacked in
@file{~/sepia}, it can be installed by adding the following lines to
@file{~/.emacs}:

@example
(add-to-list 'load-path "~/sepia")
(setq sepia-perl5lib (expand-file-name "~/sepia/lib"))
(defalias 'perl-mode 'sepia-mode)
@end example

Then to bring up the interactive Perl prompt, type @kbd{M-x sepia-repl}.

@node Philosophy,  , Getting Started, Introduction
@section Philosophy

A development environment should support three activities: code
spelunking, interaction, and customization.  Emacs as an environment for
developing Emacs Lisp thoroughly supports all of them: It has commands
to visit individual functions' code and documentation, commands to
evaluate or step through expressions, and an architecture that
encourages customization in Emacs Lisp.  As an environment for Perl,
however, it is lacking: there is limited interactivity with the Perl
debugger, and reasonable documentation browsing, but no support for
navigating, editing, and re-evaluating code.  Sepia attempts to remedy
the situation.

Modern IDEs also support these three activities, but do so awkwardly.
Rather than having functions to visit definitions (@kbd{find-function})
and search for functions (@kbd{apropos}), they clutter the screen with
class and file trees.  Rather than supporting interactive evaluation of
small pieces of code, they perform background semantic checking on whole
projects and highlight errors.  Rather than allowing minor
customizations to grow organically into features, they support limited
configuration files and baroque plug-in APIs.  Sepia tries to adhere to
the apparent Emacs philosophy that rich semantic information should be
unobtrusive, and that the best way to build working code is to start
by experimenting with small pieces.

Language support packages for Emacs vary widely in the degree to which
they make use of or replace existing Emacs features.  Minimal modes
provide keyword-based syntax highlighting and an unadorned comint buffer
as an interpreter.  Others provide their own specialized equivalents of
comint, eldoc, completion, and other Emacs features.  Sepia takes a
third approach by trying to do as much as possible with existing Emacs
features, even when they are not optimal for Perl.  It uses comint to
communicate with the subprocess, eldoc to display documentation, and
grep to list source locations.

This approach has three advantages: First, it maximizes the number of
features that can be supported with limited development time.  Second,
it respects users' settings.  A seasoned Emacs user may have changed
hundreds of settings, so a mode that reimplements features will have to
support equivalent settings, and will force the user to re-specify them.
Finally, this approach respects decades of development spent, as Neal
Stephenson put it, ``focused with maniacal intensity on the deceptively
simple-seeming problem of editing text.''  Many non-obvious choices go
into making a polished interface, and while a reimplementation gets rid
of accumulated cruft, it must rediscover these hidden trade-offs.

Anyways, I hope you enjoy using Sepia.  Its development style is strange
for someone used Perl's typical mix of one-liners and edit-save-run, but
once you are accustomed to it, you may find it very effective.

@c ============================================================
@node Editing, Interactive Perl, Introduction, Top
@chapter Editing

Sepia's first contribution is a set of commands to explore a Perl
codebase.  These include commands to browse and display documentation,
to find function definitions, and to query a cross-reference database of
function and variable uses.  Sepia also provides intelligent symbol
completion.

@menu
* Completion::                  
* Navigation::                  
* Documentation::               
@end menu

@node Completion, Navigation, Editing, Editing
@section Completion

Sepia implements fairly sophisticated partial-word completion in
collaboration with the inferior Perl process.  For example,
@samp{%S:X:v_u} completes to @samp{%Sepia::Xref::var_use} when Sepia is
loaded.  This completion only operates on functions and global variables
known to the Perl interpreter, so it works best when code and
interpreter are in sync.

More precisely, completion examines the text before point and tries each
of the following in turn, using the first successful approach:

@enumerate
@item
If the text looks like a method call (e.g. @samp{$object->f} or
@samp{Class->f}), complete on methods.

@item
If it looks like a variable, complete on variables; otherwise, complete
on modules and functions.

@item
Otherwise, try to complete a Perl built-in operator.
@end enumerate

For each of the first two, completions candidates are first generated by
splitting the text on characters @code{[:_]} and matching the resulting
word parts.  For example, @samp{X:a_b} will complete to all symbols
matching @samp{^X[^:]*:a[^:_]*_b} such as @samp{Xref::a_bug} and
@samp{X::always_bites_me}.  If no matches result, the text is treated as
an acronym.  For example, @samp{dry} will complete to
@samp{dont_repeat_yourself}.

@table @kbd
@item M-x sepia-complete-symbol
@findex sepia-complete-symbol
Complete the symbol before point as either a module, function, methd, or
global variable.  Note that this does not consider lexical scope, and is
always case-sensitive, independent of @code{completion-ignore-case}.

@item TAB
@itemx M-x sepia-indent-or-complete
@findex sepia-indent-or-complete
First try to indent the current line.  If the indentation does not
change, then try to expand an abbrev at point (unless
@code{sepia-indent-expand-abbrev} is @code{NIL}).  If no abbrev is
expanded, then call @code{sepia-complete-symbol}.

@end table

@node Navigation, Documentation, Completion, Editing
@section Navigation

Sepia provides several commands for navigating program source.  All of
them rely on information from the inferior Perl process, so it is
important both that it be running, and that its internal representation
of the program matches the program on disk.  The commands marked (Xref)
below also rely on a cross-reference database, which must be explicitly
rebuilt by calling @code{xref-rebuild} when the program changes.

There are two basic kinds of navigation commands.  The first kind jump
directly to the first matching location when possible, prompting only if
no such location is found.  These commands find only a single location,
and do not put their results on the found-location ring.

@c direct-jump commands
@table @kbd

@item M-. M-.
@itemx M-x sepia-dwim
@findex sepia-dwim
Guess what kind of identifier is at point, and try to do the right
thing: for a function, find its definition(s); for a variable, find its
uses; for a module, view its documentation; otherwise, prompt for the
name of a function to visit.  @code{sepia-dwim} automatically goes to
the first function definition or variable use found.

@item M-. l
@itemx M-x sepia-location
@findex sepia-location
Jump directly to the definition of the function at point, prompting if
point is not on a symbol.  If multiple definitions are found, choose one
arbitrarily.  This function is similar to @code{sepia-defs}, and the two
should probably be merged.

@item M-. j
@itemx M-x sepia-jump-to-symbol
@findex sepia-jump-to-symbol
Navigate to a function using ``ido'' interactive completion.  Within
interactive completion, press @key{:} to descend into a package,
@key{DEL} to ascend to a parent package, and @key{RET} to go to the
currently-selected function.

@end table

The second kind of navigation commands always prompt the user -- though
usually with a sensible default value -- and find multiple locations.
When called with a prefix argument, these commands present their results
in a @code{grep-mode} buffer.  When called @emph{without} a prefix
argument, these commands place all results on the found-location ring
and jump directly to the first.  The remaining locations can be cycled
through by calls to @code{sepia-next}.

@c prompt-and-go commands
@table @kbd
@item M-. f @var{name} @key{RET}
@itemx M-x sepia-defs
@findex sepia-defs
Find definition(s) of function @var{name}.

@item M-. m
@itemx M-x sepia-module-find @var{name} @key{RET}
@findex sepia-module-find
Find the source of module @var{name}.

@item M-. a @var{regexp} @key{RET}
@itemx M-x sepia-apropos @var{regexp} @key{RET}
@findex sepia-apropos
Find definitions of all functions whose names match @var{regexp}.

@item M-. c @var{name} @key{RET}
@itemx M-x sepia-callers @var{name} @key{RET}
@findex sepia-callers
(Xref) Find calls to function @var{name}.

@item M-. C @var{name} @key{RET}
@itemx M-x sepia-callees @var{name} @key{RET}
@findex sepia-callees
(Xref) Find the definitions of functions called by @var{name}.

@item M-. v @var{name} @key{RET}
@itemx M-x sepia-var-uses @var{name} @key{RET}
@findex sepia-var-uses
(Xref) Find uses of the global variable @var{name}.

@item M-. V @var{name} @key{RET}
@itemx M-x sepia-var-defs @var{name} @key{RET}
@findex sepia-var-defs
(Xref) Find definitions of global variable @var{name}.  Since Perl's
global variables are not declared, this is rarely useful

@c XXX: broken, so don't mention it.
@c @item M-. A @var{regexp} @key{RET}
@c @itemx M-x sepia-var-apropos
@c @findex sepia-var-apropos
@c Find definitions of all variables whose names match @var{regexp}.  Since
@c this function does not handle lexical variables, and since Perl's global
@c variables are not declared, this is rarely useful.

@end table

Finally, there are several other navigation-related commands that do not
fit into either of the above categories.

@c other commands
@table @kbd
@item M-. n
@itemx M-x sepia-next
@findex sepia-next
Cycle through the definitions found by the previous @key{M-.} search.

@item M-. r
@itemx M-x sepia-rebuild
@findex sepia-rebuild
Rebuild the cross-reference database by walking the op-tree and
stashes.

@item M-. t
@itemx M-x find-tag
Execute the @code{find-tag} command typically bound to @key{M-.}.

@end table

@node Documentation,  , Navigation, Editing
@section Documentation

Sepia can be used to browse installed modules' documentation, to format
and display the current buffer's POD, and to browse the list of modules
installed on the system.

@table @kbd
@item M-. d @var{name} @key{RET}
@itemx M-x sepia-perldoc-this
@findex sepia-perldoc-this
View documentation for module @var{name} or Perl manual page @var{name}.

@item C-c C-d
@itemx M-x sepia-view-pod
@findex sepia-view-pod
Format and view the current buffer's documentation.

@item sepia-package-list
@findex sepia-package-list
Browse a tree of installed packages.  This lists only the top-level
packages from installed distributions, so if package @code{My::Stuff}
also provides @code{My::Stuff::Details}, it will not be displayed.  When
Emacs-w3m is available, each module is linked to its documentation.

@item sepia-module-list
@findex sepia-module-list
Browse a tree of both top-level and internal packages, like
@code{sepia-package-list}.

@end table

@findex sepia-install-eldoc
Sepia also integrates with eldoc (at least in GNU Emacs >= 22).  To
toggle eldoc support, type @kbd{M-x sepia-install-eldoc}.  Documentation
for Perl operators and control structures is taken from CPerl mode.
Sepia can also display documentation for user-defined functions if their
POD is formatted in the standard way, with functions described in a
``=head2'' or ``=item'' entry.  To load user documentation, visit the
relevant file and type @kbd{M-x sepia-doc-update}.

If @code{Module::CoreList} is available Sepia's eldoc function will also
display the first version of Perl in which a module was shipped by
default.  This is intended to give the programmer a sense of when he is
creating external dependencies.

@c ============================================================
@node Interactive Perl, Customization, Editing, Top
@chapter Interactive Perl

Sepia's second main contribution is an interactive interface (REPL) to
an inferior Perl process in comint mode.  The interface is based on
comint-mode, and inherits many of its bindings; this chapter discusses
only the Sepia extensions.  In addition to the standard interactive
REPL, Sepia provides a number of other ways to evaluate pieces of code
in Perl, and commands to process buffer regions with Perl.

@findex sepia-repl
To start or switch to the repl, type @kbd{M-x sepia-repl}.  As
sepia-mode, @key{TAB} in the REPL performs partial-word completion with
@code{sepia-complete-symbol}.  However, it also supports filename
completion like standard comint mode.

@menu
* Shortcuts::                   
* Debugger::                    
* Evaluation::                  
* Mutilation::                  
* Scratchpad::                  
@end menu

@node Shortcuts, Debugger, Interactive Perl, Interactive Perl
@section Shortcuts

``Shortcuts'' are commands handled specially by the REPL rather than
being evaluated as perl code.  They either communicate with the REPL
function, or provide a convenient interface to variables in the Sepia
package.  Shortcuts are prefixed by a comma (@key{,}), and may be
abbreviated to the shortest unique prefix.

@table @kbd
@item cd @var{dir}
Change perl's current directory to @var{dir}.

@item format @var{type}
Set the output format to @var{type}, either ``dumper'' (using
@code{Data::Dumper}), ``dump'' (@code{Data::Dump}), ``yaml''
(@code{YAML}), or ``plain'' (stringification).  Default: ``dumper''.

@item help
Display a list of shortcuts.

@item methods @var{name} [@var{regexp}]
Display a list of functions defined in package @var{name} and its
@code{ISA}-ancestors matching optional pattern @var{regexp}.

@item package @var{name}
Set the default evaluation package to @var{name}.

@item quit
Exit the inferior Perl process.

@item reload
Reload @file{Sepia.pm} and recursively invoke the REPL.  This command is
mostly of interest when working on Sepia itself.

@item strict [@var{val}]
Set evaluation strictness to @var{val}, or toggle it if @var{val} is not
given.  Note that turning strictness off and on clears the REPL's
lexical environment.

@item wantarray [@var{val}]
Set the evaluation context to @var{val}, or toggle between scalar and
array context.

@item who [@var{name} [@var{regexp}]]
List identifiers in package @var{name} (main by default) matching
optional pattern @var{regexp}.

@end table

@node Debugger, Evaluation, Shortcuts, Interactive Perl
@section Debugger

Unfortunately Sepia does @emph{not} use Perl's debugger hooks, so it
does not support a true debugger with breakpoints, single-stepping, etc.
However, the REPL overrides the @code{die()} and @code{warn()}
operators, allowing it to intercept failures while their context is
still available.  This makes it possible to produce a backtrace, inspect
and modify global variables, and continue execution.  If the PadWalker
module is available, Sepia also provides functions to inspect and modify
lexical variables.

The debugger has its own set of shortcuts, also prefixed by a comma.

@table @kbd
@item backtrace
Show a backtrace with @code{Carp::cluck}.

@item inspect @var{n}
Inspect lexicals in frame @var{n}, counting upward (requires PadWalker).

@item eval @var{n} @var{expr}
Evaluate @var{expr} in the lexical environment of frame @var{n}
(requires PadWalker).  @var{expr} should not transfer control out of
this environment, but is free to modify its lexicals.

@item return @var{expr}
Continue execution as if @code{die()} or @code{warn()} had returned the
value of @var{expr}, which is evaluated in the global environment.

@item die
@itemx warn
Continue dying or warning as the program would have done without
debugger intervention.

@end table

@node Evaluation, Mutilation, Debugger, Interactive Perl
@section Evaluation

When interactive Perl is running, Sepia can evaluate regions of code in
the inferior Perl process.  The following commands assume that this
process has already been started by calling @code{sepia-repl}.

@table @kbd
@item C-M-x
@itemx M-x sepia-eval-defun
@findex sepia-eval-defun
Evaluate the function around point in the inferior Perl process.

@item C-c C-l
@itemx M-x sepia-load-file
@findex sepia-load-file
Save the current buffer, then reload its file and if warnings or errors
occur, display an error buffer.  With a prefix argument, also rebuild
the cross-reference index.

@item C-c e
@itemx M-x sepia-eval-expression @key{RET} @var{expr} @key{RET}
@findex sepia-eval-expression
Evaluate @var{expr} in scalar context and echo the result.  With a
prefix argument, evaluate in list context.

@item sepia-set-cwd

@end table

@node Mutilation, Scratchpad, Evaluation, Interactive Perl
@section Mutilation

Sepia contains several functions to operate on regions of text using the
interactive Perl process.  These functions can be used like standard
one-liners (e.g. @samp{perl -pe ...}), with the advantage that all of
the functions and variables in the interactive session are available.

@table @kbd
@item M-x sepia-perl-pe-region @key{RET} @var{code} @key{RET}
@findex sepia-perl-pe-region
Evaluate @var{code} on each line in the region with @code{$_} bound to
the line text, collecting the resulting values of @code{$_}.  With a
prefix argument, replace the region with the result.

@item M-x sepia-perl-ne-region @key{RET} @var{code} @key{RET}
@findex sepia-perl-ne-region
Evaluate @var{code} as above, but collect the @emph{results} of code.

@item M-x sepia-perlize-region @key{RET} @var{code} @key{RET}
@findex sepia-perlize-region
Evaluate @var{code} once with @code{$_} bound to the entire region,
collecting the final value of @code{$_}.  With a prefix argument,
replace the region.

@end table

@node Scratchpad,  , Mutilation, Interactive Perl
@section Scratchpad

@findex sepia-scratch
Sepia also supports a scratchpad, another form of interaction inspired
by Emacs' @code{*scratch*} buffer.  To create or switch to the
scratchpad, type @kbd{M-x sepia-scratch}.  Scratchpad mode is exactly
like Sepia mode, except @key{C-j} evaluates the current line and prints
the result on the next line.

@c ============================================================
@node Customization, Internals, Interactive Perl, Top
@chapter Customization

While Sepia can be customized in both the Perl and Emacs Lisp, most of
the user-accessible configuration is in the latter.  The two variables
most likely to need customization are @kbd{sepia-program-name} and
@kbd{sepia-perl5lib}.  Since Sepia tries where possible to reuse
existing Emacs functionality, its behavior should already be covered by
existing customizations.

@menu
* Emacs Variables::             
* Perl Variables::              
@end menu

@node Emacs Variables, Perl Variables, Customization, Customization
@section Emacs Variables

@table @kbd

@item sepia-complete-methods
If non-@code{NIL}, @code{sepia-complete-symbol} will complete
simple method calls of the form @code{$x->} or @code{Module->}.  Since
the former requires evaluation of @code{$x}, this can be disabled.
Default: @code{T}.

@item sepia-eval-defun-include-decls
If non-@code{NIL}, attempt to generate a declaration list for
@code{sepia-eval-defun}.  This is necessary when evaluating some code,
such as that calling functions without parentheses, because the presence
of declarations affects the parsing of barewords.  Default: @code{T}.

@item sepia-indent-expand-abbrev
If non-@code{NIL}, @code{sepia-indent-or-complete} will, if
reindentation does not change the current line, expand an abbreviation
before point rather than performing completion.  Only if no abbreviation
is found will it perform completion.  Default: @code{T}.

@item sepia-module-list-function
The function to view a tree of installed modules.  Default:
@code{w3m-find-file} if Emacs-w3m is installed, or
@code{browse-url-of-buffer} otherwise.

@item sepia-perldoc-function
The function called to view installed modules' documentation.  Default:
@code{w3m-perldoc} if Emacs-w3m is installed, or @code{cperl-perldoc}
otherwise.

@item sepia-perl5lib
A list of directories to include in @code{PERL5LIB} when starting
interactive Perl.  Default: @code{NIL}.

@item sepia-prefix-key
The prefix to use for for functions in @code{sepia-keymap}.  Default:
@key{M-.}.

@item sepia-program-name
The Perl program name for interactive Perl.  Default: ``perl''.

@item sepia-use-completion
If non-@code{NIL}, various Sepia functions will generate completion
candidates from interactive Perl when called interactively.  This may be
slow or undesirable in some situations.  Default: @code{T}.

@item sepia-view-pod-function
The function called to view the current buffer's documentation.
Default: @code{sepia-w3m-view-pod} if Emacs-w3m is available, or
@code{sepia-perldoc-buffer} otherwise.

@end table

@node Perl Variables,  , Emacs Variables, Customization
@section Perl Variables

The following variables in the Sepia package control various aspects of
interactive evaluation.

@table @code

@item $PACKAGE
The package in which user input is evaluated, determined automatically
when code is evaluated from a buffer.  Default: @code{main}.

@item $PRINTER
The function called to format interactive output, normally set with the
@code{printer} shortcut.

@item $PRINT_PRETTY
If true, format some values nicely independent of the value of
@code{$PRINTER}.  Currently, this means columnating lists of simple
scalars.  Default: true.

@item $PS1
The trailing end of the prompt string, which should end with ``> ''.
Default: @code{"> "}.

@item $STOPDIE
If true, calls to @code{die} from interactive code will invoke the Sepia
debugger.  Default: true.

@item $STOPWARN
If true, calls to @code{warn} from interactive code will invoke the
Sepia debugger.  Default: false.

@item $WANTARRAY
If true, evaluate interactive expressions in list context.  Default: true.

@end table

@c ============================================================
@node Internals, Credits, Customization, Top
@chapter Internals

Many things remain unexplained except by the code itself, and some
details mentioned above should probably be given less prominence.  For
developer documentation, please see the POD for @code{Sepia} and
@code{Sepia::Xref}, and the doc-strings in @file{sepia.el}.

@node Credits, Function Index, Internals, Top
@unnumbered Credits

I would like to thank Hilko Bengen for finding and motivating me to fix
a bunch of bugs, and for doing the Debian packaging.

I would also like to thank the authors of Emacs-w3m, SLIME, ido, and
B::Xref for the code I stole.

@c ============================================================
@node Function Index,  , Credits, Top
@unnumbered Function Index
@printindex fn

@bye