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| 1 #!/usr/bin/python | |
| 2 # Copyright (c) 2011, the Dart project authors. Please see the AUTHORS file | |
| 3 # for details. All rights reserved. Use of this source code is governed by a | |
| 4 # BSD-style license that can be found in the LICENSE file. | |
| 5 | |
| 6 # Template loader and preprocessor. | |
| 7 # | |
| 8 # Preprocessor language: | |
| 9 # | |
| 10 # //$ Comment line removed by preprocessor | |
| 11 # $if VAR | |
| 12 # $else | |
| 13 # $endif | |
| 14 # | |
| 15 # VAR must be defined in the conditions dictionary. | |
| 16 | |
| 17 import os | |
| 18 | |
| 19 class TemplateLoader(object): | |
| 20 """Loads template files from a path.""" | |
| 21 | |
| 22 def __init__(self, root, subpaths, conditions = {}): | |
| 23 """Initializes loader. | |
| 24 | |
| 25 Args: | |
| 26 root - a string, the directory under which the templates are stored. | |
| 27 subpaths - a list of strings, subpaths of root in search order. | |
| 28 conditions - a dictionay from strings to booleans. Any conditional | |
| 29 expression must be a key in the map. | |
| 30 """ | |
| 31 self._root = root | |
| 32 self._subpaths = subpaths | |
| 33 self._conditions = conditions | |
| 34 self._cache = {} | |
| 35 | |
| 36 def TryLoad(self, name): | |
| 37 """Returns content of template file as a string, or None of not found.""" | |
| 38 if name in self._cache: | |
| 39 return self._cache[name] | |
| 40 | |
| 41 for subpath in self._subpaths: | |
| 42 template_file = os.path.join(self._root, subpath, name) | |
| 43 if os.path.exists(template_file): | |
| 44 template = ''.join(open(template_file).readlines()) | |
| 45 template = self._Preprocess(template, template_file) | |
| 46 self._cache[name] = template | |
| 47 return template | |
| 48 | |
| 49 return None | |
| 50 | |
| 51 def Load(self, name): | |
| 52 """Returns contents of template file as a string, or raises an exception.""" | |
| 53 template = self.TryLoad(name) | |
| 54 if template is not None: # Can be empty string | |
| 55 return template | |
| 56 raise Exception("Could not find template '%s' on %s / %s" % ( | |
| 57 name, self._root, self._subpaths)) | |
| 58 | |
| 59 def _Preprocess(self, template, filename): | |
| 60 def error(lineno, message): | |
| 61 raise Exception('%s:%s: %s' % (filename, lineno, message)) | |
| 62 | |
| 63 lines = template.splitlines(True) | |
| 64 out = [] | |
| 65 | |
| 66 condition_stack = [] | |
| 67 active = True | |
| 68 seen_else = False | |
| 69 | |
| 70 for (lineno, full_line) in enumerate(lines): | |
| 71 line = full_line.strip() | |
| 72 | |
| 73 if line.startswith('$'): | |
| 74 words = line.split() | |
| 75 directive = words[0] | |
| 76 | |
| 77 if directive == '$if': | |
| 78 if len(words) != 2: | |
| 79 error(lineno, '$if does not have single variable') | |
| 80 variable = words[1] | |
| 81 if variable in self._conditions: | |
| 82 condition_stack.append((active, seen_else)) | |
| 83 active = self._conditions[variable] | |
| 84 seen_else = False | |
| 85 else: | |
| 86 error(lineno, "Unknown $if variable '%s'" % variable) | |
| 87 | |
| 88 elif directive == '$else': | |
| 89 if not condition_stack: | |
| 90 error(lineno, '$else without $if') | |
| 91 if seen_else: | |
| 92 raise error(lineno, 'Double $else') | |
| 93 seen_else = True | |
| 94 active = not active | |
| 95 | |
| 96 elif directive == '$endif': | |
| 97 if not condition_stack: | |
| 98 error(lineno, '$endif without $if') | |
| 99 (active, seen_else) = condition_stack.pop() | |
| 100 | |
| 101 else: | |
| 102 # Something else, like '$!MEMBERS' | |
| 103 if active: | |
| 104 out.append(full_line) | |
| 105 elif line.startswith('//$'): | |
| 106 pass # Ignore pre-processor comment. | |
| 107 | |
| 108 else: | |
| 109 if active: | |
| 110 out.append(full_line) | |
| 111 continue | |
| 112 | |
| 113 if condition_stack: | |
| 114 error(len(lines), 'Unterminated $if') | |
| 115 | |
| 116 return ''.join(out) | |
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