IDL parser rewrite in Python

Source/bindings/scripts/idl_validator.py

+# 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):
+    if idl_attributes_filename is None:
+        return

[haraken, 2013/07/17 02:44:49]

You might want to output an error for this case.

[Nils Barth (inactive), 2013/07/17 12:05:09]

Fixed by refactoring.
This “return” is because the IDL extended attributes file is optional
(ditto with dependencies resolution), and we’re doing all the checking
at the bottom.
I moved the checks that there’s a filename into read_idl_definitions,
which makes these functions clearer and makes it explicit that the
dependency resolution and attribute validation can be skipped.

+    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.

[haraken, 2013/07/17 02:44:49]

I think postmortem processing sounds reasonable.

[Nils Barth (inactive), 2013/07/17 12:05:09]

(See longer reply.)

[Nils Barth (inactive), 2013/07/17 12:11:02]

It’s not a big deal either way, but validating while parsing would
let us report the exact line number of an error, and would have
simpler code: we’d just add a check in p_ExtendedAttribute, avoiding
having to walk the tree or special-case the merged attributes.

I’ll look into this later when simplifying the parser (moving things 
upstream), and if it turns out to be messier that way, I’ll just
remove this comment (ok if I leave for now?).

[haraken, 2013/07/21 14:31:50]

Sounds like a plan. I don't have a strong opinion about where the validation
check is conducted.

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

Got it; we’ll see what makes sense when actually trying it out.

+        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):
+        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.strip())
+        for value in value_list:
+            if value not in valid_values:

[haraken, 2013/07/17 02:44:49]

Don't you need to do value.strip() ?

[Nils Barth (inactive), 2013/07/17 12:05:09]

Nope, since the parser has already handled whitespace:
the values are tokens, hence no whitespace.
(We need to handle whitespace ourselves when reading the extended
attributes file though.)
Actually, I don’t even need to do values_string.strip(),
so removed for consistency!

+                raise IDLInvalidExtendedAttributeError('Invalid value "{value}" found in extended attribute [{name}={value_string}]'.format(**locals()))