1 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 # Use of this source code is governed by a BSD-style license that can be
3 # found in the LICENSE file.
6 """A convenience object for constructing code.
8 Logically each object should be a block of code. All methods except |Render|
9 and |IsEmpty| return self.
11 def __init__(self, indent_size=2, comment_length=80):
13 self._indent_level = 0
14 self._indent_size = indent_size
15 self._comment_length = comment_length
17 def Append(self, line='', substitute=True, indent_level=None):
18 """Appends a line of code at the current indent level or just a newline if
19 line is not specified. Trailing whitespace is stripped.
21 substitute: indicated whether this line should be affected by
24 if indent_level is None:
25 indent_level = self._indent_level
26 self._code.append(Line(((' ' * indent_level) + line).rstrip(),
27 substitute=substitute))
31 """Returns True if the Code object is empty.
33 return not bool(self._code)
35 def Concat(self, obj):
36 """Concatenate another Code object onto this one. Trailing whitespace is
39 Appends the code at the current indent level. Will fail if there are any
40 un-interpolated format specifiers eg %s, %(something)s which helps
41 isolate any strings that haven't been substituted.
43 if not isinstance(obj, Code):
44 raise TypeError(type(obj))
45 assert self is not obj
46 for line in obj._code:
48 # line % () will fail if any substitution tokens are left in line
52 raise TypeError('Unsubstituted value when concatting\n' + line.value)
54 raise ValueError('Stray % character when concatting\n' + line.value)
55 self.Append(line.value, line.substitute)
59 def Cblock(self, code):
60 """Concatenates another Code object |code| onto this one followed by a
61 blank line, if |code| is non-empty."""
62 if not code.IsEmpty():
63 self.Concat(code).Append()
66 def Sblock(self, line=None):
67 """Starts a code block.
69 Appends a line of code and then increases the indent level.
73 self._indent_level += self._indent_size
76 def Eblock(self, line=None):
77 """Ends a code block by decreasing and then appending a line (or a blank
80 # TODO(calamity): Decide if type checking is necessary
81 #if not isinstance(line, basestring):
83 self._indent_level -= self._indent_size
88 def Comment(self, comment, comment_prefix='// '):
89 """Adds the given string as a comment.
91 Will split the comment if it's too long. Use mainly for variable length
92 comments. Otherwise just use code.Append('// ...') for comments.
94 Unaffected by code.Substitute().
96 max_len = self._comment_length - self._indent_level - len(comment_prefix)
97 while len(comment) >= max_len:
98 line = comment[0:max_len]
99 last_space = line.rfind(' ')
101 line = line[0:last_space]
102 comment = comment[last_space + 1:]
104 comment = comment[max_len:]
105 self.Append(comment_prefix + line, substitute=False)
106 self.Append(comment_prefix + comment, substitute=False)
109 def Substitute(self, d):
110 """Goes through each line and interpolates using the given dict.
112 Raises type error if passed something that isn't a dict
114 Use for long pieces of code using interpolation with the same variables
115 repeatedly. This will reduce code and allow for named placeholders which
118 if not isinstance(d, dict):
119 raise TypeError('Passed argument is not a dictionary: ' + d)
120 for i, line in enumerate(self._code):
121 if self._code[i].substitute:
122 # Only need to check %s because arg is a dict and python will allow
123 # '%s %(named)s' but just about nothing else
124 if '%s' in self._code[i].value or '%r' in self._code[i].value:
125 raise TypeError('"%s" or "%r" found in substitution. '
126 'Named arguments only. Use "%" to escape')
127 self._code[i].value = line.value % d
128 self._code[i].substitute = False
132 """Renders Code as a string.
134 return '\n'.join([l.value for l in self._code])
139 def __init__(self, value, substitute=True):
141 self.substitute = substitute