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 #define ERR_LATE_FUTURE \
  12 "from __future__ imports must occur at the beginning of the file"
  13
  14 static int
  15 future_check_features(PyFutureFeatures *ff, stmt_ty s, const char *filename)
  16 {
  17         int i;
  18         asdl_seq *names;
  19
  20         assert(s->kind == ImportFrom_kind);
  21
  22         names = s->v.ImportFrom.names;
  23         for (i = 0; i < asdl_seq_LEN(names); i++) {
  24                 alias_ty name = (alias_ty)asdl_seq_GET(names, i);
  25                 const char *feature = PyString_AsString(name->name);
  26                 if (!feature)
  27                         return 0;
  28                 if (strcmp(feature, FUTURE_NESTED_SCOPES) == 0) {
  29                         continue;
  30                 } else if (strcmp(feature, FUTURE_GENERATORS) == 0) {
  31                         continue;
  32                 } else if (strcmp(feature, FUTURE_DIVISION) == 0) {
  33                         ff->ff_features |= CO_FUTURE_DIVISION;
  34                 } else if (strcmp(feature, FUTURE_ABSOLUTE_IMPORT) == 0) {
  35                         ff->ff_features |= CO_FUTURE_ABSOLUTE_IMPORT;
  36                 } else if (strcmp(feature, FUTURE_WITH_STATEMENT) == 0) {
  37                         ff->ff_features |= CO_FUTURE_WITH_STATEMENT;
  38                 } else if (strcmp(feature, FUTURE_PRINT_FUNCTION) == 0) {
  39                         ff->ff_features |= CO_FUTURE_PRINT_FUNCTION;
  40                 } else if (strcmp(feature, FUTURE_UNICODE_LITERALS) == 0) {
  41                         ff->ff_features |= CO_FUTURE_UNICODE_LITERALS;
  42                 } else if (strcmp(feature, "braces") == 0) {
  43                         PyErr_SetString(PyExc_SyntaxError,
  44                                         "not a chance");
  45                         PyErr_SyntaxLocation(filename, s->lineno);
  46                         return 0;
  47                 } else {
  48                         PyErr_Format(PyExc_SyntaxError,
  49                                      UNDEFINED_FUTURE_FEATURE, feature);
  50                         PyErr_SyntaxLocation(filename, s->lineno);
  51                         return 0;
  52                 }
  53         }
  54         return 1;
  55 }
  56
  57 static int
  58 future_parse(PyFutureFeatures *ff, mod_ty mod, const char *filename)
  59 {
  60         int i, found_docstring = 0, done = 0, prev_line = 0;
  61
  62         static PyObject *future;
  63         if (!future) {
  64                 future = PyString_InternFromString("__future__");
  65                 if (!future)
  66                         return 0;
  67         }
  68
  69         if (!(mod->kind == Module_kind || mod->kind == Interactive_kind))
  70                 return 1;
  71
  72         /* A subsequent pass will detect future imports that don't
  73            appear at the beginning of the file.  There's one case,
  74            however, that is easier to handle here: A series of imports
  75            joined by semi-colons, where the first import is a future
  76            statement but some subsequent import has the future form
  77            but is preceded by a regular import.
  78         */
  79
  80
  81         for (i = 0; i < asdl_seq_LEN(mod->v.Module.body); i++) {
  82                 stmt_ty s = (stmt_ty)asdl_seq_GET(mod->v.Module.body, i);
  83
  84                 if (done && s->lineno > prev_line)
  85                         return 1;
  86                 prev_line = s->lineno;
  87
  88                 /* The tests below will return from this function unless it is
  89                    still possible to find a future statement.  The only things
  90                    that can precede a future statement are another future
  91                    statement and a doc string.
  92                 */
  93
  94                 if (s->kind == ImportFrom_kind) {
  95                         if (s->v.ImportFrom.module == future) {
  96                                 if (done) {
  97                                         PyErr_SetString(PyExc_SyntaxError,
  98                                                         ERR_LATE_FUTURE);
  99                                         PyErr_SyntaxLocation(filename,
 100                                                              s->lineno);
 101                                         return 0;
 102                                 }
 103                                 if (!future_check_features(ff, s, filename))
 104                                         return 0;
 105                                 ff->ff_lineno = s->lineno;
 106                         }
 107                         else
 108                                 done = 1;
 109                 }
 110                 else if (s->kind == Expr_kind && !found_docstring) {
 111                         expr_ty e = s->v.Expr.value;
 112                         if (e->kind != Str_kind)
 113                                 done = 1;
 114                         else
 115                                 found_docstring = 1;
 116                 }
 117                 else
 118                         done = 1;
 119         }
 120         return 1;
 121 }
 122
 123
 124 PyFutureFeatures *
 125 PyFuture_FromAST(mod_ty mod, const char *filename)
 126 {
 127         PyFutureFeatures *ff;
 128
 129         ff = (PyFutureFeatures *)PyObject_Malloc(sizeof(PyFutureFeatures));
 130         if (ff == NULL) {
 131                 PyErr_NoMemory();
 132                 return NULL;
 133         }
 134         ff->ff_features = 0;
 135         ff->ff_lineno = -1;
 136
 137         if (!future_parse(ff, mod, filename)) {
 138                 PyObject_Free(ff);
 139                 return NULL;
 140         }
 141         return ff;
 142 }