manifest: add a --json output option

Sometimes parsing JSON is easier than parsing XML, especially when
the XML format is limited (which ours is).  Add a --json option to
the manifest command to quickly emit that form.

Bug: https://crbug.com/gerrit/11743
Change-Id: Ia2bb254a78ae2b70a851638b4545fcafe8c1a76b
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/280436
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

manifest_xml.py

@@ -283,9 +283,8 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
   def _ParseGroups(self, groups):
     return [x for x in re.split(r'[,\s]+', groups) if x]
 
-  def Save(self, fd, peg_rev=False, peg_rev_upstream=True, peg_rev_dest_branch=True, groups=None):
-    """Write the current manifest out to the given file descriptor.
-    """
+  def ToXml(self, peg_rev=False, peg_rev_upstream=True, peg_rev_dest_branch=True, groups=None):
+    """Return the current manifest XML."""
     mp = self.manifestProject
 
     if groups is None:
@@ -459,6 +458,56 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                      ' '.join(self._repo_hooks_project.enabled_repo_hooks))
       root.appendChild(e)
 
+    return doc
+
+  def ToDict(self, **kwargs):
+    """Return the current manifest as a dictionary."""
+    # Elements that may only appear once.
+    SINGLE_ELEMENTS = {
+        'notice',
+        'default',
+        'manifest-server',
+        'repo-hooks',
+    }
+    # Elements that may be repeated.
+    MULTI_ELEMENTS = {
+        'remote',
+        'remove-project',
+        'project',
+        'extend-project',
+        'include',
+        # These are children of 'project' nodes.
+        'annotation',
+        'project',
+        'copyfile',
+        'linkfile',
+    }
+
+    doc = self.ToXml(**kwargs)
+    ret = {}
+
+    def append_children(ret, node):
+      for child in node.childNodes:
+        if child.nodeType == xml.dom.Node.ELEMENT_NODE:
+          attrs = child.attributes
+          element = dict((attrs.item(i).localName, attrs.item(i).value)
+                         for i in range(attrs.length))
+          if child.nodeName in SINGLE_ELEMENTS:
+            ret[child.nodeName] = element
+          elif child.nodeName in MULTI_ELEMENTS:
+            ret.setdefault(child.nodeName, []).append(element)
+          else:
+            raise ManifestParseError('Unhandled element "%s"' % (child.nodeName,))
+
+          append_children(element, child)
+
+    append_children(ret, doc.firstChild)
+
+    return ret
+
+  def Save(self, fd, **kwargs):
+    """Write the current manifest out to the given file descriptor."""
+    doc = self.ToXml(**kwargs)
     doc.writexml(fd, '', '  ', '\n', 'UTF-8')
 
   def _output_manifest_project_extras(self, p, e):

subcmds/manifest.py

@@ -15,6 +15,8 @@
 # limitations under the License.
 
 from __future__ import print_function
+
+import json
 import os
 import sys
 
@@ -68,6 +70,10 @@ to indicate the remote ref to push changes to via 'repo upload'.
                  help='If in -r mode, do not write the dest-branch field.  '
                  'Only of use if the branch names for a sha1 manifest are '
                  'sensitive.')
+    p.add_option('--json', default=False, action='store_true',
+                 help='Output manifest in JSON format (experimental).')
+    p.add_option('--pretty', default=False, action='store_true',
+                 help='Format output for humans to read.')
     p.add_option('-o', '--output-file',
                  dest='output_file',
                  default='-',
@@ -83,10 +89,26 @@ to indicate the remote ref to push changes to via 'repo upload'.
       fd = sys.stdout
     else:
       fd = open(opt.output_file, 'w')
-    self.manifest.Save(fd,
-                       peg_rev=opt.peg_rev,
-                       peg_rev_upstream=opt.peg_rev_upstream,
-                       peg_rev_dest_branch=opt.peg_rev_dest_branch)
+    if opt.json:
+      print('warning: --json is experimental!', file=sys.stderr)
+      doc = self.manifest.ToDict(peg_rev=opt.peg_rev,
+                                 peg_rev_upstream=opt.peg_rev_upstream,
+                                 peg_rev_dest_branch=opt.peg_rev_dest_branch)
+
+      json_settings = {
+          # JSON style guide says Uunicode characters are fully allowed.
+          'ensure_ascii': False,
+          # We use 2 space indent to match JSON style guide.
+          'indent': 2 if opt.pretty else None,
+          'separators': (',', ': ') if opt.pretty else (',', ':'),
+          'sort_keys': True,
+      }
+      fd.write(json.dumps(doc, **json_settings))
+    else:
+      self.manifest.Save(fd,
+                         peg_rev=opt.peg_rev,
+                         peg_rev_upstream=opt.peg_rev_upstream,
+                         peg_rev_dest_branch=opt.peg_rev_dest_branch)
     fd.close()
     if opt.output_file != '-':
       print('Saved manifest to %s' % opt.output_file, file=sys.stderr)