Python/future.c

   1 #include "Python.h"
   2 #include "Python-ast.h"
   3 #include "node.h"
   4 #include "token.h"
   5 #include "graminit.h"
   6 #include "code.h"
   7 #include "compile.h"
   8 #include "symtable.h"
   9
  10 #define UNDEFINED_FUTURE_FEATURE "future feature %.100s is not defined"
  11
  12 static int
  13 future_check_features(PyFutureFeatures *ff, stmt_ty s, const char *filename)
  14 {
  15         int i;
  16         asdl_seq *names;
  17
  18         assert(s->kind == ImportFrom_kind);
  19
  20         names = s->v.ImportFrom.names;
  21         for (i = 0; i < asdl_seq_LEN(names); i++) {
  22                 alias_ty name = asdl_seq_GET(names, i);
  23                 const char *feature = PyString_AsString(name->name);
  24                 if (!feature)
  25                         return 0;
  26                 if (strcmp(feature, FUTURE_NESTED_SCOPES) == 0) {
  27                         continue;
  28                 } else if (strcmp(feature, FUTURE_GENERATORS) == 0) {
  29                         continue;
  30                 } else if (strcmp(feature, FUTURE_DIVISION) == 0) {
  31                         ff->ff_features |= CO_FUTURE_DIVISION;
  32                 } else if (strcmp(feature, "braces") == 0) {
  33                         PyErr_SetString(PyExc_SyntaxError,
  34                                         "not a chance");
  35                         PyErr_SyntaxLocation(filename, s->lineno);
  36                         return 0;
  37                 } else {
  38                         PyErr_Format(PyExc_SyntaxError,
  39                                      UNDEFINED_FUTURE_FEATURE, feature);
  40                         PyErr_SyntaxLocation(filename, s->lineno);
  41                         return 0;
  42                 }
  43         }
  44         return 1;
  45 }
  46
  47 static int
  48 future_parse(PyFutureFeatures *ff, mod_ty mod, const char *filename)
  49 {
  50         int i, found_docstring = 0, done = 0, prev_line = 0;
  51
  52         static PyObject *future;
  53         if (!future) {
  54                 future = PyString_InternFromString("__future__");
  55                 if (!future)
  56                         return 0;
  57         }
  58
  59         if (!(mod->kind == Module_kind || mod->kind == Interactive_kind))
  60                 return 1;
  61
  62         /* A subsequent pass will detect future imports that don't
  63            appear at the beginning of the file.  There's one case,
  64            however, that is easier to handl here: A series of imports
  65            joined by semi-colons, where the first import is a future
  66            statement but some subsequent import has the future form
  67            but is preceded by a regular import.
  68         */
  69
  70
  71         for (i = 0; i < asdl_seq_LEN(mod->v.Module.body); i++) {
  72                 stmt_ty s = asdl_seq_GET(mod->v.Module.body, i);
  73
  74                 if (done && s->lineno > prev_line)
  75                         return 1;
  76                 prev_line = s->lineno;
  77
  78                 /* The tests below will return from this function unless it is
  79                    still possible to find a future statement.  The only things
  80                    that can precede a future statement are another future
  81                    statement and a doc string.
  82                 */
  83
  84                 if (s->kind == ImportFrom_kind) {
  85                         if (s->v.ImportFrom.module == future) {
  86                                 if (done) {
  87                                         PyErr_SetString(PyExc_SyntaxError,
  88                                                         ERR_LATE_FUTURE);
  89                                         PyErr_SyntaxLocation(filename,
  90                                                              s->lineno);
  91                                         return 0;
  92                                 }
  93                                 if (!future_check_features(ff, s, filename))
  94                                         return 0;
  95                                 ff->ff_lineno = s->lineno;
  96                         }
  97                         else
  98                                 done = 1;
  99                 }
 100                 else if (s->kind == Expr_kind && !found_docstring) {
 101                         expr_ty e = s->v.Expr.value;
 102                         if (e->kind != Str_kind)
 103                                 done = 1;
 104                         else
 105                                 found_docstring = 1;
 106                 }
 107                 else
 108                         done = 1;
 109         }
 110         return 1;
 111 }
 112
 113
 114 PyFutureFeatures *
 115 PyFuture_FromAST(mod_ty mod, const char *filename)
 116 {
 117         PyFutureFeatures *ff;
 118
 119         ff = (PyFutureFeatures *)PyMem_Malloc(sizeof(PyFutureFeatures));
 120         if (ff == NULL)
 121                 return NULL;
 122         ff->ff_features = 0;
 123         ff->ff_lineno = -1;
 124
 125         if (!future_parse(ff, mod, filename)) {
 126                 PyMem_Free((void *)ff);
 127                 return NULL;
 128         }
 129         return ff;
 130 }