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| 1 | r"""Utilities to compile possibly incomplete Python source code. | ||
| 2 | |||
| 3 | This module provides two interfaces, broadly similar to the builtin | ||
| 4 | function compile(), which take program text, a filename and a 'mode' | ||
| 5 | and: | ||
| 6 | |||
| 7 | - Return code object if the command is complete and valid | ||
| 8 | - Return None if the command is incomplete | ||
| 9 | - Raise SyntaxError, ValueError or OverflowError if the command is a | ||
| 10 | syntax error (OverflowError and ValueError can be produced by | ||
| 11 | malformed literals). | ||
| 12 | |||
| 13 | Approach: | ||
| 14 | |||
| 15 | First, check if the source consists entirely of blank lines and | ||
| 16 | comments; if so, replace it with 'pass', because the built-in | ||
| 17 | parser doesn't always do the right thing for these. | ||
| 18 | |||
| 19 | Compile three times: as is, with \n, and with \n\n appended. If it | ||
| 20 | compiles as is, it's complete. If it compiles with one \n appended, | ||
| 21 | we expect more. If it doesn't compile either way, we compare the | ||
| 22 | error we get when compiling with \n or \n\n appended. If the errors | ||
| 23 | are the same, the code is broken. But if the errors are different, we | ||
| 24 | expect more. Not intuitive; not even guaranteed to hold in future | ||
| 25 | releases; but this matches the compiler's behavior from Python 1.4 | ||
| 26 | through 2.2, at least. | ||
| 27 | |||
| 28 | Caveat: | ||
| 29 | |||
| 30 | It is possible (but not likely) that the parser stops parsing with a | ||
| 31 | successful outcome before reaching the end of the source; in this | ||
| 32 | case, trailing symbols may be ignored instead of causing an error. | ||
| 33 | For example, a backslash followed by two newlines may be followed by | ||
| 34 | arbitrary garbage. This will be fixed once the API for the parser is | ||
| 35 | better. | ||
| 36 | |||
| 37 | The two interfaces are: | ||
| 38 | |||
| 39 | compile_command(source, filename, symbol): | ||
| 40 | |||
| 41 | Compiles a single command in the manner described above. | ||
| 42 | |||
| 43 | CommandCompiler(): | ||
| 44 | |||
| 45 | Instances of this class have __call__ methods identical in | ||
| 46 | signature to compile_command; the difference is that if the | ||
| 47 | instance compiles program text containing a __future__ statement, | ||
| 48 | the instance 'remembers' and compiles all subsequent program texts | ||
| 49 | with the statement in force. | ||
| 50 | |||
| 51 | The module also provides another class: | ||
| 52 | |||
| 53 | Compile(): | ||
| 54 | |||
| 55 | Instances of this class act like the built-in function compile, | ||
| 56 | but with 'memory' in the sense described above. | ||
| 57 | """ | ||
| 58 | |||
| 59 | import __future__ | ||
| 60 | |||
| 61 | _features = [getattr(__future__, fname) | ||
| 62 | for fname in __future__.all_feature_names] | ||
| 63 | |||
| 64 | __all__ = ["compile_command", "Compile", "CommandCompiler"] | ||
| 65 | |||
| 66 | PyCF_DONT_IMPLY_DEDENT = 0x200 # Matches pythonrun.h | ||
| 67 | |||
| 68 | def _maybe_compile(compiler, source, filename, symbol): | ||
| 69 | # Check for source consisting of only blank lines and comments | ||
| 70 | for line in source.split("\n"): | ||
| 71 | line = line.strip() | ||
| 72 | if line and line[0] != '#': | ||
| 73 | break # Leave it alone | ||
| 74 | else: | ||
| 75 | if symbol != "eval": | ||
| 76 | source = "pass" # Replace it with a 'pass' statement | ||
| 77 | |||
| 78 | err = err1 = err2 = None | ||
| 79 | code = code1 = code2 = None | ||
| 80 | |||
| 81 | try: | ||
| 82 | code = compiler(source, filename, symbol) | ||
| 83 | except SyntaxError, err: | ||
| 84 | pass | ||
| 85 | |||
| 86 | try: | ||
| 87 | code1 = compiler(source + "\n", filename, symbol) | ||
| 88 | except SyntaxError, err1: | ||
| 89 | pass | ||
| 90 | |||
| 91 | try: | ||
| 92 | code2 = compiler(source + "\n\n", filename, symbol) | ||
| 93 | except SyntaxError, err2: | ||
| 94 | pass | ||
| 95 | |||
| 96 | if code: | ||
| 97 | return code | ||
| 98 | if not code1 and repr(err1) == repr(err2): | ||
| 99 | raise SyntaxError, err1 | ||
| 100 | |||
| 101 | def _compile(source, filename, symbol): | ||
| 102 | return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT) | ||
| 103 | |||
| 104 | def compile_command(source, filename="<input>", symbol="single"): | ||
| 105 | r"""Compile a command and determine whether it is incomplete. | ||
| 106 | |||
| 107 | Arguments: | ||
| 108 | |||
| 109 | source -- the source string; may contain \n characters | ||
| 110 | filename -- optional filename from which source was read; default | ||
| 111 | "<input>" | ||
| 112 | symbol -- optional grammar start symbol; "single" (default) or "eval" | ||
| 113 | |||
| 114 | Return value / exceptions raised: | ||
| 115 | |||
| 116 | - Return a code object if the command is complete and valid | ||
| 117 | - Return None if the command is incomplete | ||
| 118 | - Raise SyntaxError, ValueError or OverflowError if the command is a | ||
| 119 | syntax error (OverflowError and ValueError can be produced by | ||
| 120 | malformed literals). | ||
| 121 | """ | ||
| 122 | return _maybe_compile(_compile, source, filename, symbol) | ||
| 123 | |||
| 124 | class Compile: | ||
| 125 | """Instances of this class behave much like the built-in compile | ||
| 126 | function, but if one is used to compile text containing a future | ||
| 127 | statement, it "remembers" and compiles all subsequent program texts | ||
| 128 | with the statement in force.""" | ||
| 129 | def __init__(self): | ||
| 130 | self.flags = PyCF_DONT_IMPLY_DEDENT | ||
| 131 | |||
| 132 | def __call__(self, source, filename, symbol): | ||
| 133 | codeob = compile(source, filename, symbol, self.flags, 1) | ||
| 134 | for feature in _features: | ||
| 135 | if codeob.co_flags & feature.compiler_flag: | ||
| 136 | self.flags |= feature.compiler_flag | ||
| 137 | return codeob | ||
| 138 | |||
| 139 | class CommandCompiler: | ||
| 140 | """Instances of this class have __call__ methods identical in | ||
| 141 | signature to compile_command; the difference is that if the | ||
| 142 | instance compiles program text containing a __future__ statement, | ||
| 143 | the instance 'remembers' and compiles all subsequent program texts | ||
| 144 | with the statement in force.""" | ||
| 145 | |||
| 146 | def __init__(self,): | ||
| 147 | self.compiler = Compile() | ||
| 148 | |||
| 149 | def __call__(self, source, filename="<input>", symbol="single"): | ||
| 150 | r"""Compile a command and determine whether it is incomplete. | ||
| 151 | |||
| 152 | Arguments: | ||
| 153 | |||
| 154 | source -- the source string; may contain \n characters | ||
| 155 | filename -- optional filename from which source was read; | ||
| 156 | default "<input>" | ||
| 157 | symbol -- optional grammar start symbol; "single" (default) or | ||
| 158 | "eval" | ||
| 159 | |||
| 160 | Return value / exceptions raised: | ||
| 161 | |||
| 162 | - Return a code object if the command is complete and valid | ||
| 163 | - Return None if the command is incomplete | ||
| 164 | - Raise SyntaxError, ValueError or OverflowError if the command is a | ||
| 165 | syntax error (OverflowError and ValueError can be produced by | ||
| 166 | malformed literals). | ||
| 167 | """ | ||
| 168 | return _maybe_compile(self.compiler, source, filename, symbol) | ||