360 lines
12 KiB
Python
Executable File
360 lines
12 KiB
Python
Executable File
#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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# Copyright 2014 The Chromium Authors. All rights reserved.
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# Use of this source code is governed by a BSD-style license that can be
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# found in the LICENSE file.
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"""Helper functions useful when writing scripts that integrate with GN.
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The main functions are ToGNString and FromGNString which convert between
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serialized GN variables and Python variables.
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To use in a random python file in the build:
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import os
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import sys
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sys.path.append(os.path.join(os.path.dirname(__file__),
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os.pardir, os.pardir, "build"))
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import gn_helpers
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Where the sequence of parameters to join is the relative path from your source
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file to the build directory.
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"""
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class GNException(Exception):
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pass
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def ToGNString(value, allow_dicts=True):
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"""Returns a stringified GN equivalent of the Python value.
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allow_dicts indicates if this function will allow converting dictionaries
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to GN scopes. This is only possible at the top level, you can't nest a
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GN scope in a list, so this should be set to False for recursive calls."""
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if isinstance(value, str):
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if value.find('\n') >= 0:
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raise GNException("Trying to print a string with a newline in it.")
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return '"' + \
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value.replace('\\', '\\\\').replace('"', '\\"').replace('$', '\\$') + \
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'"'
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if isinstance(value, str):
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return ToGNString(value.encode('utf-8'))
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if isinstance(value, bool):
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if value:
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return "true"
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return "false"
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if isinstance(value, list):
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return '[ %s ]' % ', '.join(ToGNString(v) for v in value)
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if isinstance(value, dict):
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if not allow_dicts:
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raise GNException("Attempting to recursively print a dictionary.")
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result = ""
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for key in sorted(value):
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if not isinstance(key, str):
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raise GNException("Dictionary key is not a string.")
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result += "%s = %s\n" % (key, ToGNString(value[key], False))
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return result
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if isinstance(value, int):
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return str(value)
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raise GNException("Unsupported type when printing to GN.")
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def FromGNString(input_string):
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"""Converts the input string from a GN serialized value to Python values.
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For details on supported types see GNValueParser.Parse() below.
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If your GN script did:
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something = [ "file1", "file2" ]
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args = [ "--values=$something" ]
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The command line would look something like:
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--values="[ \"file1\", \"file2\" ]"
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Which when interpreted as a command line gives the value:
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[ "file1", "file2" ]
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You can parse this into a Python list using GN rules with:
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input_values = FromGNValues(options.values)
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Although the Python 'ast' module will parse many forms of such input, it
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will not handle GN escaping properly, nor GN booleans. You should use this
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function instead.
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A NOTE ON STRING HANDLING:
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If you just pass a string on the command line to your Python script, or use
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string interpolation on a string variable, the strings will not be quoted:
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str = "asdf"
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args = [ str, "--value=$str" ]
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Will yield the command line:
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asdf --value=asdf
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The unquoted asdf string will not be valid input to this function, which
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accepts only quoted strings like GN scripts. In such cases, you can just
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use the Python string literal directly.
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The main use cases for this is for other types, in particular lists. When
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using string interpolation on a list (as in the top example) the embedded
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strings will be quoted and escaped according to GN rules so the list can be
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re-parsed to get the same result.
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"""
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parser = GNValueParser(input_string)
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return parser.Parse()
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def FromGNArgs(input_string):
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"""Converts a string with a bunch of gn arg assignments into a Python dict.
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Given a whitespace-separated list of
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<ident> = (integer | string | boolean | <list of the former>)
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gn assignments, this returns a Python dict, i.e.:
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FromGNArgs("foo=true\nbar=1\n") -> { 'foo': True, 'bar': 1 }.
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Only simple types and lists supported; variables, structs, calls
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and other, more complicated things are not.
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This routine is meant to handle only the simple sorts of values that
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arise in parsing --args.
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"""
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parser = GNValueParser(input_string)
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return parser.ParseArgs()
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def UnescapeGNString(value):
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"""Given a string with GN escaping, returns the unescaped string.
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Be careful not to feed with input from a Python parsing function like
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'ast' because it will do Python unescaping, which will be incorrect when
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fed into the GN unescaper."""
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result = ''
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i = 0
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while i < len(value):
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if value[i] == '\\':
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if i < len(value) - 1:
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next_char = value[i + 1]
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if next_char in ('$', '"', '\\'):
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# These are the escaped characters GN supports.
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result += next_char
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i += 1
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else:
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# Any other backslash is a literal.
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result += '\\'
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else:
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result += value[i]
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i += 1
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return result
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def _IsDigitOrMinus(char):
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return char in "-0123456789"
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class GNValueParser(object):
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"""Duplicates GN parsing of values and converts to Python types.
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Normally you would use the wrapper function FromGNValue() below.
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If you expect input as a specific type, you can also call one of the Parse*
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functions directly. All functions throw GNException on invalid input.
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"""
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def __init__(self, string):
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self.input = string
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self.cur = 0
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def IsDone(self):
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return self.cur == len(self.input)
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def ConsumeWhitespace(self):
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while not self.IsDone() and self.input[self.cur] in ' \t\n':
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self.cur += 1
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def Parse(self):
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"""Converts a string representing a printed GN value to the Python type.
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See additional usage notes on FromGNString above.
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- GN booleans ('true', 'false') will be converted to Python booleans.
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- GN numbers ('123') will be converted to Python numbers.
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- GN strings (double-quoted as in '"asdf"') will be converted to Python
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strings with GN escaping rules. GN string interpolation (embedded
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variables preceded by $) are not supported and will be returned as
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literals.
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- GN lists ('[1, "asdf", 3]') will be converted to Python lists.
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- GN scopes ('{ ... }') are not supported.
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"""
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result = self._ParseAllowTrailing()
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self.ConsumeWhitespace()
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if not self.IsDone():
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raise GNException("Trailing input after parsing:\n " +
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self.input[self.cur:])
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return result
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def ParseArgs(self):
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"""Converts a whitespace-separated list of ident=literals to a dict.
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See additional usage notes on FromGNArgs, above.
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"""
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d = {}
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self.ConsumeWhitespace()
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while not self.IsDone():
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ident = self._ParseIdent()
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self.ConsumeWhitespace()
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if self.input[self.cur] != '=':
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raise GNException("Unexpected token: " + self.input[self.cur:])
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self.cur += 1
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self.ConsumeWhitespace()
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val = self._ParseAllowTrailing()
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self.ConsumeWhitespace()
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d[ident] = val
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return d
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def _ParseAllowTrailing(self):
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"""Internal version of Parse that doesn't check for trailing stuff."""
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self.ConsumeWhitespace()
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if self.IsDone():
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raise GNException("Expected input to parse.")
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next_char = self.input[self.cur]
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if next_char == '[':
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return self.ParseList()
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elif _IsDigitOrMinus(next_char):
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return self.ParseNumber()
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elif next_char == '"':
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return self.ParseString()
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elif self._ConstantFollows('true'):
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return True
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elif self._ConstantFollows('false'):
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return False
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else:
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raise GNException("Unexpected token: " + self.input[self.cur:])
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def _ParseIdent(self):
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ident = ''
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next_char = self.input[self.cur]
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if not next_char.isalpha() and not next_char == '_':
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raise GNException("Expected an identifier: " + self.input[self.cur:])
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ident += next_char
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self.cur += 1
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next_char = self.input[self.cur]
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while next_char.isalpha() or next_char.isdigit() or next_char == '_':
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ident += next_char
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self.cur += 1
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next_char = self.input[self.cur]
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return ident
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def ParseNumber(self):
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self.ConsumeWhitespace()
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if self.IsDone():
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raise GNException('Expected number but got nothing.')
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begin = self.cur
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# The first character can include a negative sign.
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if not self.IsDone() and _IsDigitOrMinus(self.input[self.cur]):
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self.cur += 1
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while not self.IsDone() and self.input[self.cur].isdigit():
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self.cur += 1
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number_string = self.input[begin:self.cur]
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if not len(number_string) or number_string == '-':
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raise GNException("Not a valid number.")
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return int(number_string)
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def ParseString(self):
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self.ConsumeWhitespace()
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if self.IsDone():
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raise GNException('Expected string but got nothing.')
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if self.input[self.cur] != '"':
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raise GNException('Expected string beginning in a " but got:\n ' +
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self.input[self.cur:])
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self.cur += 1 # Skip over quote.
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begin = self.cur
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while not self.IsDone() and self.input[self.cur] != '"':
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if self.input[self.cur] == '\\':
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self.cur += 1 # Skip over the backslash.
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if self.IsDone():
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raise GNException("String ends in a backslash in:\n " +
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self.input)
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self.cur += 1
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if self.IsDone():
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raise GNException('Unterminated string:\n ' + self.input[begin:])
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end = self.cur
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self.cur += 1 # Consume trailing ".
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return UnescapeGNString(self.input[begin:end])
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def ParseList(self):
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self.ConsumeWhitespace()
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if self.IsDone():
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raise GNException('Expected list but got nothing.')
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# Skip over opening '['.
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if self.input[self.cur] != '[':
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raise GNException("Expected [ for list but got:\n " +
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self.input[self.cur:])
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self.cur += 1
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self.ConsumeWhitespace()
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if self.IsDone():
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raise GNException("Unterminated list:\n " + self.input)
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list_result = []
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previous_had_trailing_comma = True
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while not self.IsDone():
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if self.input[self.cur] == ']':
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self.cur += 1 # Skip over ']'.
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return list_result
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if not previous_had_trailing_comma:
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raise GNException("List items not separated by comma.")
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list_result += [self._ParseAllowTrailing()]
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self.ConsumeWhitespace()
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if self.IsDone():
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break
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# Consume comma if there is one.
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previous_had_trailing_comma = self.input[self.cur] == ','
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if previous_had_trailing_comma:
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# Consume comma.
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self.cur += 1
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self.ConsumeWhitespace()
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raise GNException("Unterminated list:\n " + self.input)
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def _ConstantFollows(self, constant):
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"""Returns true if the given constant follows immediately at the
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current location in the input. If it does, the text is consumed and
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the function returns true. Otherwise, returns false and the current
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position is unchanged."""
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end = self.cur + len(constant)
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if end > len(self.input):
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return False # Not enough room.
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if self.input[self.cur:end] == constant:
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self.cur = end
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return True
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return False
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