1r"""Utilities to compile possibly incomplete Python source code. 2 3This module provides two interfaces, broadly similar to the builtin 4function compile(), which take program text, a filename and a 'mode' 5and: 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 13Approach: 14 15First, check if the source consists entirely of blank lines and 16comments; if so, replace it with 'pass', because the built-in 17parser doesn't always do the right thing for these. 18 19Compile three times: as is, with \n, and with \n\n appended. If it 20compiles as is, it's complete. If it compiles with one \n appended, 21we expect more. If it doesn't compile either way, we compare the 22error we get when compiling with \n or \n\n appended. If the errors 23are the same, the code is broken. But if the errors are different, we 24expect more. Not intuitive; not even guaranteed to hold in future 25releases; but this matches the compiler's behavior from Python 1.4 26through 2.2, at least. 27 28Caveat: 29 30It is possible (but not likely) that the parser stops parsing with a 31successful outcome before reaching the end of the source; in this 32case, trailing symbols may be ignored instead of causing an error. 33For example, a backslash followed by two newlines may be followed by 34arbitrary garbage. This will be fixed once the API for the parser is 35better. 36 37The two interfaces are: 38 39compile_command(source, filename, symbol): 40 41 Compiles a single command in the manner described above. 42 43CommandCompiler(): 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 51The module also provides another class: 52 53Compile(): 54 55 Instances of this class act like the built-in function compile, 56 but with 'memory' in the sense described above. 57""" 58 59import __future__ 60import warnings 61 62_features = [getattr(__future__, fname) 63 for fname in __future__.all_feature_names] 64 65__all__ = ["compile_command", "Compile", "CommandCompiler"] 66 67PyCF_DONT_IMPLY_DEDENT = 0x200 # Matches pythonrun.h 68 69def _maybe_compile(compiler, source, filename, symbol): 70 # Check for source consisting of only blank lines and comments 71 for line in source.split("\n"): 72 line = line.strip() 73 if line and line[0] != '#': 74 break # Leave it alone 75 else: 76 if symbol != "eval": 77 source = "pass" # Replace it with a 'pass' statement 78 79 err = err1 = err2 = None 80 code = code1 = code2 = None 81 82 try: 83 code = compiler(source, filename, symbol) 84 except SyntaxError as err: 85 pass 86 87 # Suppress warnings after the first compile to avoid duplication. 88 with warnings.catch_warnings(): 89 warnings.simplefilter("ignore") 90 try: 91 code1 = compiler(source + "\n", filename, symbol) 92 except SyntaxError as e: 93 err1 = e 94 95 try: 96 code2 = compiler(source + "\n\n", filename, symbol) 97 except SyntaxError as e: 98 err2 = e 99 100 try: 101 if code: 102 return code 103 if not code1 and repr(err1) == repr(err2): 104 raise err1 105 finally: 106 err1 = err2 = None 107 108def _compile(source, filename, symbol): 109 return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT) 110 111def compile_command(source, filename="<input>", symbol="single"): 112 r"""Compile a command and determine whether it is incomplete. 113 114 Arguments: 115 116 source -- the source string; may contain \n characters 117 filename -- optional filename from which source was read; default 118 "<input>" 119 symbol -- optional grammar start symbol; "single" (default), "exec" 120 or "eval" 121 122 Return value / exceptions raised: 123 124 - Return a code object if the command is complete and valid 125 - Return None if the command is incomplete 126 - Raise SyntaxError, ValueError or OverflowError if the command is a 127 syntax error (OverflowError and ValueError can be produced by 128 malformed literals). 129 """ 130 return _maybe_compile(_compile, source, filename, symbol) 131 132class Compile: 133 """Instances of this class behave much like the built-in compile 134 function, but if one is used to compile text containing a future 135 statement, it "remembers" and compiles all subsequent program texts 136 with the statement in force.""" 137 def __init__(self): 138 self.flags = PyCF_DONT_IMPLY_DEDENT 139 140 def __call__(self, source, filename, symbol): 141 codeob = compile(source, filename, symbol, self.flags, 1) 142 for feature in _features: 143 if codeob.co_flags & feature.compiler_flag: 144 self.flags |= feature.compiler_flag 145 return codeob 146 147class CommandCompiler: 148 """Instances of this class have __call__ methods identical in 149 signature to compile_command; the difference is that if the 150 instance compiles program text containing a __future__ statement, 151 the instance 'remembers' and compiles all subsequent program texts 152 with the statement in force.""" 153 154 def __init__(self,): 155 self.compiler = Compile() 156 157 def __call__(self, source, filename="<input>", symbol="single"): 158 r"""Compile a command and determine whether it is incomplete. 159 160 Arguments: 161 162 source -- the source string; may contain \n characters 163 filename -- optional filename from which source was read; 164 default "<input>" 165 symbol -- optional grammar start symbol; "single" (default) or 166 "eval" 167 168 Return value / exceptions raised: 169 170 - Return a code object if the command is complete and valid 171 - Return None if the command is incomplete 172 - Raise SyntaxError, ValueError or OverflowError if the command is a 173 syntax error (OverflowError and ValueError can be produced by 174 malformed literals). 175 """ 176 return _maybe_compile(self.compiler, source, filename, symbol) 177