add metrics_xml_formatter

git cl format supports formatting certain xml files under tools/metrics.
This CL adds metrics_xml_formatter so that the formatter can be run
with git cl format.

Bug: b/369827156
Change-Id: I5922cd79304aa8e06917aacc9f2d9bd3ed548c2f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/6072565
Reviewed-by: Josip Sokcevic <sokcevic@chromium.org>
Commit-Queue: Scott Lee <ddoman@chromium.org>

metrics_xml_format.py

@@ -0,0 +1,121 @@
+#!/usr/bin/env vpython3
+# Copyright (c) 2024 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Redirects to the version of the metrics XML formatter in the Chromium tree.
+"""
+import gclient_paths
+import os
+import shutil
+import subprocess
+import sys
+
+
+def GetMetricsDir(path):
+    metrics_xml_dirs = [
+        'tools/metrics/actions',
+        'tools/metrics/histograms',
+        'tools/metrics/structured',
+        'tools/metrics/ukm',
+    ]
+    normalized_abs_dirname = os.path.dirname(os.path.abspath(path)).replace(
+        os.sep, '/')
+    for xml_dir in metrics_xml_dirs:
+        if normalized_abs_dirname.endswith(xml_dir):
+            return xml_dir
+    return None
+
+
+def IsSupportedHistogramsXML(path):
+    supported_xmls = set([
+        'histograms.xml',
+        'enums.xml',
+        'histogram_suffixes_list.xml',
+    ])
+    return os.path.basename(path) in supported_xmls
+
+
+def log(msg, verbose):
+    if verbose:
+        print(msg)
+
+
+def FindMetricsXMLFormatterTool(path, verbose=False):
+    """Returns a path to the metrics XML formatter executable."""
+    top_dir = gclient_paths.GetPrimarySolutionPath()
+    if not top_dir:
+        log('Not executed in a Chromium checkout; skip formatting', verbose)
+        return ''
+    xml_dir = GetMetricsDir(path)
+    if not xml_dir:
+        log(f'{path} is not a metric XML; skip formatting', verbose)
+        return ''
+    # Just to ensure that the given file is located in the current checkout
+    # folder. If not, skip the formatting.
+    if not os.path.abspath(path).startswith(os.path.abspath(top_dir)):
+        log(
+            f'{path} is not located in the current Chromium checkout; '
+            'skip formatting', verbose)
+        return ''
+
+    if xml_dir == 'tools/metrics/histograms':
+        # Skips the formatting, if the XML file is not one of the known types.
+        if not IsSupportedHistogramsXML(path):
+            log(f'{path} is not a supported histogram XML; skip formatting',
+                verbose)
+            return ''
+
+    # top_dir is already formatted with the OS specific path separator, whereas
+    # xml_dir is not yet.
+    tool_dir = os.path.join(top_dir, xml_dir.replace('/', os.path.sep))
+    return os.path.join(tool_dir, 'pretty_print.py')
+
+
+usage_text = """Usage: %s [option] filepath
+
+Format a given metrics XML file with the metrics XML formatters in the Chromium
+checkout. Noop, if executed out of a Chromium checkout.
+
+Note that not all the options are understood by all the formatters.
+Find the formatter binaries for all the options supported by each formatter.
+
+positional arguments:
+  filepath           if the path is not under tools/metrics,
+                     no formatter will be run.
+
+options:,
+  -h, --help          show this help message and exit'
+  --presubmit
+  --diff"""
+
+
+def _print_help():
+    print(usage_text % sys.argv[0])
+
+
+def main(args):
+    path = next((arg for arg in args if not arg.startswith('-')), None)
+    if not path:
+        _print_help()
+        return 0
+    if not os.path.exists(path):
+        raise FileNotFoundError(f'{path} does not exist.')
+
+    tool = FindMetricsXMLFormatterTool(path, verbose=True)
+    if not tool:
+        # Fail (almost) silently.
+        return 0
+
+    subprocess.run([
+        shutil.which('vpython3'),
+        tool,
+    ] + args)
+    return 0
+
+
+if __name__ == '__main__':
+    try:
+        sys.exit(main(sys.argv[1:]))
+    except KeyboardInterrupt:
+        sys.stderr.write('interrupted\n')
+        sys.exit(1)