IDL parser rewrite in Python

Source/bindings/scripts/idl_validator.py

Index: Source/bindings/scripts/idl_validator.py
diff --git a/Source/bindings/scripts/idl_validator.py b/Source/bindings/scripts/idl_validator.py
new file mode 100644
index 0000000000000000000000000000000000000000..7bf7fc5203baa44fe785a84ca7588a7fc0d33122
--- /dev/null
+++ b/Source/bindings/scripts/idl_validator.py
@@ -0,0 +1,110 @@
+# Copyright (C) 2013 Google Inc. All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+#     * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#     * Redistributions in binary form must reproduce the above
+# copyright notice, this list of conditions and the following disclaimer
+# in the documentation and/or other materials provided with the
+# distribution.
+#     * Neither the name of Google Inc. nor the names of its
+# contributors may be used to endorse or promote products derived from
+# this software without specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+"""Validate extended attributes."""
+
+
+import re
+
+
+class IDLExtendedAttributeFileFormatError(Exception):
+    pass
+
+
+class IDLInvalidExtendedAttributeError(Exception):
+    pass
+
+
+def validate_extended_attributes(definitions, basename, idl_attributes_filename):
+    extended_attribute_validator = IDLExtendedAttributeValidator(idl_attributes_filename)
+    extended_attribute_validator.validate_extended_attributes(definitions, basename)
+
+
+def read_extended_attributes_file(extended_attributes_filename):
+    valid_extended_attributes = {}
+    with open(extended_attributes_filename) as extended_attributes_file:
+        for line in extended_attributes_file:
+            line = line.strip()
+            if not line or line.startswith('#'):
+                continue
+            name, _, values_string = map(str.strip, line.partition('='))
+            if not name:
+                raise IDLExtendedAttributeFileFormatError('The format of %s is wrong, in line "%s"' % (extended_attributes_filename, line))
+            valid_extended_attributes[name] = set()
+            value_list = values_string.split('|')
+            if not value_list:
+                valid_extended_attributes[name].add(None)
+                continue
+            for value in value_list:
+                value = value.strip()
+                if not value:
+                    value = None
+                valid_extended_attributes[name].add(value)
+    return valid_extended_attributes
+
+
+class IDLExtendedAttributeValidator:
+    def __init__(self, extended_attributes_filename):
+        self.valid_extended_attributes = read_extended_attributes_file(extended_attributes_filename)
+
+    def validate_extended_attributes(self, definitions, idl_filename):
+        # FIXME: this should be done when parsing the file, rather than after.
+        try:
+            for interface in definitions.interfaces.itervalues():
+                self.validate_extended_attributes_node(interface)
+                for attribute in interface.attributes:
+                    self.validate_extended_attributes_node(attribute)
+                for function in interface.functions:
+                    self.validate_extended_attributes_node(function)
+                    for argument in function.arguments:
+                        self.validate_extended_attributes_node(argument)
+        except IDLInvalidExtendedAttributeError, error:
+            raise IDLInvalidExtendedAttributeError("""IDL ATTRIBUTE ERROR in file %s:
+%s
+If you want to add a new IDL extended attribute, please add it to bindings/scripts/IDLAttributes.txt and add an explanation to the Blink IDL document at http://chromium.org/blink/webidl
+""" % (idl_filename, str(error)))
+
+    def validate_extended_attributes_node(self, node):
+        for name, value_string in node.extended_attributes.iteritems():
+            self.validate_name_value_string(name, value_string)
+
+    def validate_name_value_string(self, name, values_string):

[haraken, 2013/07/22 01:50:23]

Nit: values_string => value_string (for consistency with the method name and the
parameter name in the caller side.)

[Nils Barth (inactive), 2013/07/22 06:32:01]

Oops, good point -- this was inconsistent (elsewhere too).
I’ve actually changed to values_string to emphasize that it needs splitting.

+        if name == 'ImplementedBy':  # attribute added when merging interfaces
+            return
+        if name not in self.valid_extended_attributes:
+            raise IDLInvalidExtendedAttributeError('Unknown extended attribute [%s]' % name)
+        valid_values = self.valid_extended_attributes[name]
+        if '*' in valid_values:  # wildcard, any value ok
+            return
+        if values_string is None:
+            value_list = [None]
+        else:
+            value_list = re.split('[|&]', values_string)
+        for value in value_list:
+            if value not in valid_values:
+                raise IDLInvalidExtendedAttributeError('Invalid value "{value}" found in extended attribute [{name}={value_string}]'.format(**locals()))

[haraken, 2013/07/22 01:50:23]

Help me understand: What is .format(**locals()) for?

[Nils Barth (inactive), 2013/07/22 06:32:01]

It’s string formatting, so we can write {name} to substitute the value of the
variable ‘name’, and corresponds to “$name” in Bash or Perl.
The .format(**locals()) is ugly, but it’s the standard way to do it in Python,
and means that the format template string itself is clear.

Actually though, this is a hint that Python doesn't want you to do this.
(Lint can't see what variables you're using, for instance.)
I've replaced this with explicit variables instead (which is consistent with
other uses).

For background:
The **locals() expression says
“make named parameters from the dictionary of local variables”;
this ** is useful when passing named parameters by passing a dictionary.

The alternatives are to either:
1. use %s in the format string and listing the variables outside,
   which is a bit indirect, or
2. use %(foo)s format strings and then % locals() afterwards,
   which makes the format string a little harder to read.
The %s solution is the simplest and most explicit, so I've changed to that.

Some (long) reference:
http://stackoverflow.com/questions/1550479/python-is-using-vars-locals-a-good...