Bug 1434974 - [mozlint] Create a SummaryFormatter to help triage paths, r=jmaher

This formatter is useful for triaging paths when enabling new linters or
expanding existing ones. It works well with the -n/--no-filter option.

For example, if I wanted to look for candidates of new directories to enable
the codespell linter on, I could run:

./mach lint -l codespell -nf summary

This will print something like:
accessible: 429
dom: 142
layout: 15
testing: 53
etc..

If desired, you can also specify a depth by setting MOZLINT_SUMMARY_DEPTH. A
depth of 2 means results will be aggregated further down, e.g:

accesible/build: 129
accesible/ipc: 300
dom/indexedDB: 100
dom/workers: 42
etc..

The depth is always relative to the common path prefix of all results, so
running:

./mach lint -l codespell -nf python/mozbuild

Would expand all the directories under python/mozbuild (not topsrdir).

MozReview-Commit-ID: OiihLTpULA

--HG--
extra : rebase_source : eaaabc1d5cdc8e3942808d01b24e22081fea752e

python/mozlint/mozlint/formatters/__init__.py

@@ -9,6 +9,7 @@ import json
 from ..result import ResultEncoder
 from .compact import CompactFormatter
 from .stylish import StylishFormatter
+from .summary import SummaryFormatter
 from .treeherder import TreeherderFormatter
 from .unix import UnixFormatter
 
@@ -22,6 +23,7 @@ all_formatters = {
     'compact': CompactFormatter,
     'json': JSONFormatter,
     'stylish': StylishFormatter,
+    'summary': SummaryFormatter,
     'treeherder': TreeherderFormatter,
     'unix': UnixFormatter,
 }

python/mozlint/mozlint/formatters/summary.py

@@ -0,0 +1,35 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from __future__ import absolute_import, unicode_literals
+
+import os
+from collections import defaultdict
+
+import mozpack.path as mozpath
+
+
+class SummaryFormatter(object):
+
+    def __init__(self, depth=None):
+        self.depth = depth or int(os.environ.get('MOZLINT_SUMMARY_DEPTH', 1))
+
+    def __call__(self, result, **kwargs):
+        commonprefix = mozpath.commonprefix([mozpath.abspath(p) for p in result])
+        commonprefix = commonprefix.rsplit('/', 1)[0] + '/'
+
+        summary = defaultdict(int)
+        for path, errors in result.iteritems():
+            path = mozpath.abspath(path)
+            assert path.startswith(commonprefix)
+
+            if path == commonprefix:
+                summary[path] += len(errors)
+                continue
+
+            parts = mozpath.split(mozpath.relpath(path, commonprefix))[:self.depth]
+            path = mozpath.join(commonprefix, *parts)
+            summary[path] += len(errors)
+
+        return '\n'.join(['{}: {}'.format(k, summary[k]) for k in sorted(summary)])

python/mozlint/test/test_formatters.py

@@ -9,6 +9,7 @@ import os
 from collections import defaultdict
 
 import mozunit
+import mozpack.path as mozpath
 import pytest
 
 from mozlint import ResultContainer
@@ -17,6 +18,7 @@ from mozlint import formatters
 NORMALISED_PATHS = {
     'abc': os.path.normpath('a/b/c.txt'),
     'def': os.path.normpath('d/e/f.txt'),
+    'cwd': mozpath.normpath(os.getcwd()),
 }
 
 EXPECTED = {
@@ -59,6 +61,13 @@ TEST-UNEXPECTED-WARNING | d/e/f.txt:4:2 | oh no bar (bar-not-allowed)
 {abc}:1: foo error: oh no foo
 {abc}:4: baz error: oh no baz
 {def}:4:2: bar-not-allowed warning: oh no bar
+""".format(**NORMALISED_PATHS).strip(),
+    },
+    'summary': {
+        'kwargs': {},
+        'format': """
+{cwd}/a: 2
+{cwd}/d: 1
 """.format(**NORMALISED_PATHS).strip(),
     },
 }