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, FUTURE_ABSOLUTE_IMPORT) == 0) {
  33                         ff->ff_features |= CO_FUTURE_ABSOLUTE_IMPORT;
  34                 } else if (strcmp(feature, FUTURE_WITH_STATEMENT) == 0) {
  35                         ff->ff_features |= CO_FUTURE_WITH_STATEMENT;
  36                 } else if (strcmp(feature, "braces") == 0) {
  37                         PyErr_SetString(PyExc_SyntaxError,
  38                                         "not a chance");
  39                         PyErr_SyntaxLocation(filename, s->lineno);
  40                         return 0;
  41                 } else {
  42                         PyErr_Format(PyExc_SyntaxError,
  43                                      UNDEFINED_FUTURE_FEATURE, feature);
  44                         PyErr_SyntaxLocation(filename, s->lineno);
  45                         return 0;
  46                 }
  47         }
  48         return 1;
  49 }
  50
  51 static int
  52 future_parse(PyFutureFeatures *ff, mod_ty mod, const char *filename)
  53 {
  54         int i, found_docstring = 0, done = 0, prev_line = 0;
  55
  56         static PyObject *future;
  57         if (!future) {
  58                 future = PyString_InternFromString("__future__");
  59                 if (!future)
  60                         return 0;
  61         }
  62
  63         if (!(mod->kind == Module_kind || mod->kind == Interactive_kind))
  64                 return 1;
  65
  66         /* A subsequent pass will detect future imports that don't
  67            appear at the beginning of the file.  There's one case,
  68            however, that is easier to handl here: A series of imports
  69            joined by semi-colons, where the first import is a future
  70            statement but some subsequent import has the future form
  71            but is preceded by a regular import.
  72         */
  73
  74
  75         for (i = 0; i < asdl_seq_LEN(mod->v.Module.body); i++) {
  76                 stmt_ty s = asdl_seq_GET(mod->v.Module.body, i);
  77
  78                 if (done && s->lineno > prev_line)
  79                         return 1;
  80                 prev_line = s->lineno;
  81
  82                 /* The tests below will return from this function unless it is
  83                    still possible to find a future statement.  The only things
  84                    that can precede a future statement are another future
  85                    statement and a doc string.
  86                 */
  87
  88                 if (s->kind == ImportFrom_kind) {
  89                         if (s->v.ImportFrom.module == future) {
  90                                 if (done) {
  91                                         PyErr_SetString(PyExc_SyntaxError,
  92                                                         ERR_LATE_FUTURE);
  93                                         PyErr_SyntaxLocation(filename,
  94                                                              s->lineno);
  95                                         return 0;
  96                                 }
  97                                 if (!future_check_features(ff, s, filename))
  98                                         return 0;
  99                                 ff->ff_lineno = s->lineno;
 100                         }
 101                         else
 102                                 done = 1;
 103                 }
 104                 else if (s->kind == Expr_kind && !found_docstring) {
 105                         expr_ty e = s->v.Expr.value;
 106                         if (e->kind != Str_kind)
 107                                 done = 1;
 108                         else
 109                                 found_docstring = 1;
 110                 }
 111                 else
 112                         done = 1;
 113         }
 114         return 1;
 115 }
 116
 117
 118 PyFutureFeatures *
 119 PyFuture_FromAST(mod_ty mod, const char *filename)
 120 {
 121         PyFutureFeatures *ff;
 122
 123         ff = (PyFutureFeatures *)PyObject_Malloc(sizeof(PyFutureFeatures));
 124         if (ff == NULL)
 125                 return NULL;
 126         ff->ff_features = 0;
 127         ff->ff_lineno = -1;
 128
 129         if (!future_parse(ff, mod, filename)) {
 130                 PyObject_Free(ff);
 131                 return NULL;
 132         }
 133         return ff;
 134 }