Create jsondiff tool to capture diffs between two JSON expectations files.

tools/jsondiff.py

+#!/usr/bin/python
+
+'''
+Copyright 2013 Google Inc.
+
+Use of this source code is governed by a BSD-style license that can be
+found in the LICENSE file.
+'''
+
+'''
+Gathers diffs between 2 JSON expectations files, or between actual and
+expected results within a single JSON actual-results file,
+and generates an old-vs-new diff dictionary.

[epoger, 2013/07/02 18:24:32]

For now, this tool just generates a dictionary showing the old-vs-new checksums.
 Once I get this committed, the next steps will be:

1. rebaseline.py: if the existing expectations are stored as a JSON file rather
than image files, generate the new expectations as a JSON file also (just modify
the JSON file in the local checkout)

2. Use ExportBaseVersionOfFile() in
https://code.google.com/p/skia/source/browse/trunk/tools/svn.py , so jsondiff.py
can compare the base version of the JSON expectations file (what was checked out
from the repo) to the locally modified version.  We'll need something similar
for git.

3. Download images and call skdiff to display pixel diffs based on jsondiff's
output

+'''
+
+# System-level imports
+import argparse
+import json
+import os
+import sys
+import urllib2
+
+# Imports from within Skia
+#
+# We need to add the 'gm' directory, so that we can import gm_json.py within
+# that directory.  That script allows us to parse the actual-results.json file
+# written out by the GM tool.
+# Make sure that the 'gm' dir is in the PYTHONPATH, but add it at the *end*
+# so any dirs that are already in the PYTHONPATH will be preferred.
+#
+# This assumes that the 'gm' directory has been checked out as a sibling of
+# the 'tools' directory containing this script, which will be the case if
+# 'trunk' was checked out as a single unit.
+GM_DIRECTORY = os.path.realpath(
+    os.path.join(os.path.dirname(os.path.dirname(__file__)), 'gm'))
+if GM_DIRECTORY not in sys.path:
+    sys.path.append(GM_DIRECTORY)
+import gm_json
+
+
+# Object that generates diffs between two JSON gm result files.
+class GMDiffer(object):
+
+    def __init__(self):
+        pass
+
+    def _GetFileContentsAsString(self, filepath):
+        """Returns the full contents of a file, as a single string.
+        If the filename looks like a URL, download its contents..."""
+        if filepath.startswith('http:') or filepath.startswith('https:'):
+            return urllib2.urlopen(filepath).read()
+        else:
+            return open(filepath, 'r').read()
+
+    def _GetExpectedResults(self, filepath):
+        """Returns the dictionary of expected results from a JSON file,
+        in this form:
+
+        {
+          'test1' : 14760033689012826769,
+          'test2' : 9151974350149210736,
+          ...
+        }
+
+        We make these simplifying assumptions:
+        1. Each test has either 0 or 1 allowed results.
+        2. All expectations are of type JSONKEY_HASHTYPE_BITMAP_64BITMD5.
+
+        Any tests which violate those assumptions will cause an exception to
+        be raised.
+
+        Any tests for which we have no expectations will be left out of the
+        returned dictionary.
+        """
+        result_dict = {}
+        contents = self._GetFileContentsAsString(filepath)
+        json_dict = gm_json.LoadFromString(contents)
+        all_expectations = json_dict[gm_json.JSONKEY_EXPECTEDRESULTS]
+        for test_name in all_expectations.keys():
+            test_expectations = all_expectations[test_name]
+            allowed_digests = test_expectations[
+                gm_json.JSONKEY_EXPECTEDRESULTS_ALLOWEDDIGESTS]
+            if allowed_digests:
+                num_allowed_digests = len(allowed_digests)
+                if num_allowed_digests > 1:
+                    raise ValueError(
+                        'test %s in file %s has %d allowed digests' % (
+                            test_name, filepath, num_allowed_digests))
+                digest_pair = allowed_digests[0]
+                if digest_pair[0] != gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5:
+                    raise ValueError(
+                        'test %s in file %s has unsupported hashtype %s' % (
+                            test_name, filepath, digest_pair[0]))
+                result_dict[test_name] = digest_pair[1]
+        return result_dict
+
+    def _GetActualResults(self, filepath):
+        """Returns the dictionary of actual results from a JSON file,
+        in this form:
+
+        {
+          'test1' : 14760033689012826769,
+          'test2' : 9151974350149210736,
+          ...
+        }
+
+        We make these simplifying assumptions:
+        1. All results are of type JSONKEY_HASHTYPE_BITMAP_64BITMD5.
+
+        Any tests which violate those assumptions will cause an exception to
+        be raised.
+
+        Any tests for which we have no actual results will be left out of the
+        returned dictionary.
+        """
+        result_dict = {}
+        contents = self._GetFileContentsAsString(filepath)
+        json_dict = gm_json.LoadFromString(contents)
+        all_result_types = json_dict[gm_json.JSONKEY_ACTUALRESULTS]
+        for result_type in all_result_types.keys():
+            results_of_this_type = all_result_types[result_type]
+            if results_of_this_type:
+                for test_name in results_of_this_type.keys():
+                    digest_pair = results_of_this_type[test_name]
+                    if digest_pair[0] != gm_json.JSONKEY_HASHTYPE_BITMAP_64BITMD5:
+                        raise ValueError(
+                            'test %s in file %s has unsupported hashtype %s' % (
+                                test_name, filepath, digest_pair[0]))
+                    result_dict[test_name] = digest_pair[1]
+        return result_dict
+
+    def _DictionaryDiff(self, old_dict, new_dict):
+        """Generate a dictionary showing the diffs between old_dict and new_dict.
+        Any entries which are identical across them will be left out."""
+        diff_dict = {}
+        all_keys = set(old_dict.keys() + new_dict.keys())
+        for key in all_keys:
+            if old_dict.get(key) != new_dict.get(key):
+                new_entry = {}
+                new_entry['old'] = old_dict.get(key)
+                new_entry['new'] = new_dict.get(key)
+                diff_dict[key] = new_entry
+        return diff_dict
+
+    def GenerateDiffDict(self, oldfile, newfile=None):
+        """Generate a dictionary showing the diffs:
+        old = expectations within oldfile
+        new = expectations within newfile
+
+        If newfile is not specified, then 'new' is the actual results within
+        oldfile.
+        """
+        old_results = self._GetExpectedResults(oldfile)
+        if newfile:
+            new_results = self._GetExpectedResults(newfile)
+        else:
+            new_results = self._GetActualResults(oldfile)
+        return self._DictionaryDiff(old_results, new_results)
+
+
+# main...
+parser = argparse.ArgumentParser()
+parser.add_argument('old',
+                    help='Path to JSON file whose expectations to display on ' +
+                    'the "old" side of the diff. This can be a filepath on ' +
+                    'local storage, or a URL.')
+parser.add_argument('new', nargs='?',
+                    help='Path to JSON file whose expectations to display on ' +
+                    'the "new" side of the diff; if not specified, uses the ' +
+                    'ACTUAL results from the "old" JSON file. This can be a ' +
+                    'filepath on local storage, or a URL.')
+args = parser.parse_args()
+differ = GMDiffer()
+diffs = differ.GenerateDiffDict(oldfile=args.old, newfile=args.new)
+json.dump(diffs, sys.stdout, sort_keys=True, indent=2)