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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 | try: | |
99 | e1 = err1.__dict__ | |
100 | except AttributeError: | |
101 | e1 = err1 | |
102 | try: | |
103 | e2 = err2.__dict__ | |
104 | except AttributeError: | |
105 | e2 = err2 | |
106 | if not code1 and e1 == e2: | |
107 | raise SyntaxError, err1 | |
108 | ||
109 | def _compile(source, filename, symbol): | |
110 | return compile(source, filename, symbol, PyCF_DONT_IMPLY_DEDENT) | |
111 | ||
112 | def compile_command(source, filename="<input>", symbol="single"): | |
113 | r"""Compile a command and determine whether it is incomplete. | |
114 | ||
115 | Arguments: | |
116 | ||
117 | source -- the source string; may contain \n characters | |
118 | filename -- optional filename from which source was read; default | |
119 | "<input>" | |
120 | symbol -- optional grammar start symbol; "single" (default) 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 | ||
132 | class 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 | ||
147 | class 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) |