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