docs: sphinx and initial protodoc support for RST generation. (#212)

This takes us to the point where address.proto format in a style fairly
similar to the existing docs. There's some missing bits, e.g. oneof/enum
support, nested messages, optional/required, these will come as later
PRs.

Signed-off-by: Harvey Tuch <htuch@google.com>

.gitignore

@@ -1 +1,3 @@
 bazel-*
+build_docs/
+generated/

ci/do_ci.sh

@@ -15,8 +15,7 @@ if [[ "$1" == "bazel.test" ]]; then
   exit 0
 elif [[ "$1" == "bazel.docs" ]]; then
   echo "generating docs..."
-  bazel --batch build ${BAZEL_BUILD_OPTIONS} --aspects tools/protodoc/protodoc.bzl%proto_doc_aspect  \
-    --output_groups=rst //api
+  ./docs/build.sh
 else
   echo "Invalid do_ci.sh target. The only valid target is bazel.build."
   exit 1

ci/run_envoy_docker.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+set -e
+
+[[ -z "${IMAGE_NAME}" ]] && IMAGE_NAME="lyft/envoy-build-ubuntu"
+[[ -z "${IMAGE_ID}" ]] && IMAGE_ID="latest"
+[[ -z "${ENVOY_API_DOCKER_BUILD_DIR}" ]] && ENVOY_API_DOCKER_BUILD_DIR=/tmp/envoy-api-docker-build
+
+mkdir -p "${ENVOY_API_DOCKER_BUILD_DIR}"
+docker run -t -i -u $(id -u):$(id -g) -v "${ENVOY_API_DOCKER_BUILD_DIR}":/build \
+  -v "$PWD":/source "${IMAGE_NAME}":"${IMAGE_ID}" /bin/bash -c "cd source && $*"

docs/build.sh

@@ -0,0 +1,40 @@
+#!/bin/bash
+
+set -e
+
+SCRIPT_DIR=$(dirname "$0")
+BUILD_DIR=build_docs
+[[ -z "${DOCS_OUTPUT_DIR}" ]] && DOCS_OUTPUT_DIR=generated/docs
+[[ -z "${GENERATED_RST_DIR}" ]] && GENERATED_RST_DIR=generated/rst
+
+rm -rf "${DOCS_OUTPUT_DIR}"
+mkdir -p "${DOCS_OUTPUT_DIR}"
+
+rm -rf "${GENERATED_RST_DIR}"
+mkdir -p "${GENERATED_RST_DIR}"
+cp -f "${SCRIPT_DIR}"/{conf.py,index.rst} "${GENERATED_RST_DIR}"
+
+if [ ! -d "${BUILD_DIR}"/venv ]; then
+  virtualenv "${BUILD_DIR}"/venv --no-site-packages
+  "${BUILD_DIR}"/venv/bin/pip install -r "${SCRIPT_DIR}"/requirements.txt
+fi
+
+source "${BUILD_DIR}"/venv/bin/activate
+
+bazel --batch build -s ${BAZEL_BUILD_OPTIONS} //api --aspects \
+  tools/protodoc/protodoc.bzl%proto_doc_aspect --output_groups=rst
+
+# These are the protos we want to put in docs, this list will grow.
+# TODO(htuch): Factor this out of this script.
+PROTO_RST="
+  /api/address/api/address.proto.rst
+"
+
+# Only copy in the protos we care about and know how to deal with in protodoc.
+for p in $PROTO_RST
+do
+  mkdir -p "$(dirname "${GENERATED_RST_DIR}/$p")"
+  cp -f bazel-bin/"${p}" "${GENERATED_RST_DIR}/$p"
+done
+
+sphinx-build -W -b html "${GENERATED_RST_DIR}" "${DOCS_OUTPUT_DIR}"

docs/conf.py

@@ -0,0 +1,293 @@
+# -*- coding: utf-8 -*-
+#
+# envoy documentation build configuration file, created by
+# sphinx-quickstart on Sat May 28 10:51:27 2016.
+#
+# This file is execfile()d with the current directory set to its
+# containing dir.
+#
+# Note that not all possible configuration values are present in this
+# autogenerated file.
+#
+# All configuration values have a default; values that are commented out
+# serve to show the default.
+
+import sphinx_rtd_theme
+import sys
+import os
+import git
+
+# If extensions (or modules to document with autodoc) are in another directory,
+# add these directories to sys.path here. If the directory is relative to the
+# documentation root, use os.path.abspath to make it absolute, like shown here.
+#sys.path.insert(0, os.path.abspath('.'))
+
+# -- General configuration ------------------------------------------------
+
+# If your documentation needs a minimal Sphinx version, state it here.
+#needs_sphinx = '1.0'
+
+# Add any Sphinx extension module names here, as strings. They can be
+# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
+# ones.
+extensions = ['sphinxcontrib.httpdomain', 'sphinx.ext.extlinks']
+
+extlinks = {'repo': ('https://github.com/envoyproxy/envoy/blob/master/%s', '')}
+
+# Add any paths that contain templates here, relative to this directory.
+#templates_path = ['_templates']
+
+# The suffix(es) of source filenames.
+# You can specify multiple suffix as a list of string:
+# source_suffix = ['.rst', '.md']
+source_suffix = '.rst'
+
+# The encoding of source files.
+#source_encoding = 'utf-8-sig'
+
+# The master toctree document.
+master_doc = 'index'
+
+# General information about the project.
+project = u'envoy'
+copyright = u'2016-2017, Lyft'
+author = u'Lyft'
+
+# The version info for the project you're documenting, acts as replacement for
+# |version| and |release|, also used in various other places throughout the
+# built documents.
+
+repo = git.Repo('../../')
+last_commit = str(repo.head.commit)[:6]
+
+# The short X.Y version.
+version = u'1.5.0-' + last_commit
+# The full version, including alpha/beta/rc tags.
+release = u'1.5.0-' + last_commit
+
+# The language for content autogenerated by Sphinx. Refer to documentation
+# for a list of supported languages.
+#
+# This is also used if you do content translation via gettext catalogs.
+# Usually you set "language" from the command line for these cases.
+language = None
+
+# There are two options for replacing |today|: either, you set today to some
+# non-false value, then it is used:
+#today = ''
+# Else, today_fmt is used as the format for a strftime call.
+#today_fmt = '%B %d, %Y'
+
+# List of patterns, relative to source directory, that match files and
+# directories to ignore when looking for source files.
+# This patterns also effect to html_static_path and html_extra_path
+exclude_patterns = ['_build', '_venv', 'Thumbs.db', '.DS_Store']
+
+# The reST default role (used for this markup: `text`) to use for all
+# documents.
+#default_role = None
+
+# If true, '()' will be appended to :func: etc. cross-reference text.
+#add_function_parentheses = True
+
+# If true, the current module name will be prepended to all description
+# unit titles (such as .. function::).
+#add_module_names = True
+
+# If true, sectionauthor and moduleauthor directives will be shown in the
+# output. They are ignored by default.
+#show_authors = False
+
+# The name of the Pygments (syntax highlighting) style to use.
+pygments_style = 'sphinx'
+
+# A list of ignored prefixes for module index sorting.
+#modindex_common_prefix = []
+
+# If true, keep warnings as "system message" paragraphs in the built documents.
+#keep_warnings = False
+
+# If true, `todo` and `todoList` produce output, else they produce nothing.
+todo_include_todos = False
+
+
+# -- Options for HTML output ----------------------------------------------
+
+# The theme to use for HTML and HTML Help pages.  See the documentation for
+# a list of builtin themes.
+html_theme = 'sphinx_rtd_theme'
+
+# Theme options are theme-specific and customize the look and feel of a theme
+# further.  For a list of options available for each theme, see the
+# documentation.
+#html_theme_options = {}
+
+# Add any paths that contain custom themes here, relative to this directory.
+html_theme_path = [sphinx_rtd_theme.get_html_theme_path()]
+
+# The name for this set of Sphinx documents.
+# "<project> v<release> documentation" by default.
+#html_title = u'envoy v1.0.0'
+
+# A shorter title for the navigation bar.  Default is the same as html_title.
+#html_short_title = None
+
+# The name of an image file (relative to this directory) to place at the top
+# of the sidebar.
+#html_logo = None
+
+# The name of an image file (relative to this directory) to use as a favicon of
+# the docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
+# pixels large.
+#html_favicon = 'favicon.ico'
+
+# Add any paths that contain custom static files (such as style sheets) here,
+# relative to this directory. They are copied after the builtin static files,
+# so a file named "default.css" will overwrite the builtin "default.css".
+#html_static_path = ['_static']
+
+# Add any extra paths that contain custom files (such as robots.txt or
+# .htaccess) here, relative to this directory. These files are copied
+# directly to the root of the documentation.
+#html_extra_path = []
+
+# If not None, a 'Last updated on:' timestamp is inserted at every page
+# bottom, using the given strftime format.
+# The empty string is equivalent to '%b %d, %Y'.
+#html_last_updated_fmt = None
+
+# If true, SmartyPants will be used to convert quotes and dashes to
+# typographically correct entities.
+#html_use_smartypants = True
+
+# Custom sidebar templates, maps document names to template names.
+#html_sidebars = {}
+
+# Additional templates that should be rendered to pages, maps page names to
+# template names.
+#html_additional_pages = {}
+
+# If false, no module index is generated.
+#html_domain_indices = True
+
+# If false, no index is generated.
+#html_use_index = True
+
+# If true, the index is split into individual pages for each letter.
+#html_split_index = False
+
+# If true, links to the reST sources are added to the pages.
+#html_show_sourcelink = True
+
+# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
+#html_show_sphinx = True
+
+# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
+#html_show_copyright = True
+
+# If true, an OpenSearch description file will be output, and all pages will
+# contain a <link> tag referring to it.  The value of this option must be the
+# base URL from which the finished HTML is served.
+#html_use_opensearch = ''
+
+# This is the file name suffix for HTML files (e.g. ".xhtml").
+#html_file_suffix = None
+
+# Language to be used for generating the HTML full-text search index.
+# Sphinx supports the following languages:
+#   'da', 'de', 'en', 'es', 'fi', 'fr', 'hu', 'it', 'ja'
+#   'nl', 'no', 'pt', 'ro', 'ru', 'sv', 'tr', 'zh'
+#html_search_language = 'en'
+
+# A dictionary with options for the search language support, empty by default.
+# 'ja' uses this config value.
+# 'zh' user can custom change `jieba` dictionary path.
+#html_search_options = {'type': 'default'}
+
+# The name of a javascript file (relative to the configuration directory) that
+# implements a search results scorer. If empty, the default will be used.
+#html_search_scorer = 'scorer.js'
+
+# Output file base name for HTML help builder.
+htmlhelp_basename = 'envoydoc'
+
+# -- Options for LaTeX output ---------------------------------------------
+
+latex_elements = {
+# The paper size ('letterpaper' or 'a4paper').
+#'papersize': 'letterpaper',
+
+# The font size ('10pt', '11pt' or '12pt').
+#'pointsize': '10pt',
+
+# Additional stuff for the LaTeX preamble.
+#'preamble': '',
+
+# Latex figure (float) alignment
+#'figure_align': 'htbp',
+}
+
+# Grouping the document tree into LaTeX files. List of tuples
+# (source start file, target name, title,
+#  author, documentclass [howto, manual, or own class]).
+latex_documents = [
+    (master_doc, 'envoy.tex', u'envoy Documentation',
+     u'Lyft', 'manual'),
+]
+
+# The name of an image file (relative to this directory) to place at the top of
+# the title page.
+#latex_logo = None
+
+# For "manual" documents, if this is true, then toplevel headings are parts,
+# not chapters.
+#latex_use_parts = False
+
+# If true, show page references after internal links.
+#latex_show_pagerefs = False
+
+# If true, show URL addresses after external links.
+#latex_show_urls = False
+
+# Documents to append as an appendix to all manuals.
+#latex_appendices = []
+
+# If false, no module index is generated.
+#latex_domain_indices = True
+
+
+# -- Options for manual page output ---------------------------------------
+
+# One entry per manual page. List of tuples
+# (source start file, name, description, authors, manual section).
+man_pages = [
+    (master_doc, 'envoy', u'envoy Documentation',
+     [author], 1)
+]
+
+# If true, show URL addresses after external links.
+#man_show_urls = False
+
+
+# -- Options for Texinfo output -------------------------------------------
+
+# Grouping the document tree into Texinfo files. List of tuples
+# (source start file, target name, title, author,
+#  dir menu entry, description, category)
+texinfo_documents = [
+    (master_doc, 'envoy', u'envoy Documentation',
+     author, 'envoy', 'One line description of project.',
+     'Miscellaneous'),
+]
+
+# Documents to append as an appendix to all manuals.
+#texinfo_appendices = []
+
+# If false, no module index is generated.
+#texinfo_domain_indices = True
+
+# How to display URL addresses: 'footnote', 'no', or 'inline'.
+#texinfo_show_urls = 'footnote'
+
+# If true, do not generate a @detailmenu in the "Top" node's menu.
+#texinfo_no_detailmenu = False

docs/index.rst

@@ -0,0 +1,8 @@
+Envoy v2 API documentation
+==========================
+
+.. toctree::
+  :glob:
+  :maxdepth: 2
+
+  **

docs/requirements.txt

@@ -0,0 +1,19 @@
+GitPython==2.0.8
+Jinja2==2.9.6
+MarkupSafe==1.0
+Pygments==2.2.0
+alabaster==0.7.10
+babel==2.4.0
+docutils==0.12
+gitdb==0.6.4
+imagesize==0.7.1
+pytz==2017.2
+requests==2.13.0
+six==1.10.0
+smmap==0.9.0
+snowballstemmer==1.2.1
+sphinx==1.6.5
+sphinxcontrib-httpdomain==1.5.0
+
+# Fix for https://github.com/rtfd/sphinx_rtd_theme/issues/397
+git+https://github.com/rtfd/sphinx_rtd_theme@9d704f287ac197dfb1c9b27f0acfb91267dce4f1

tools/protodoc/protodoc.bzl

@@ -35,6 +35,18 @@ def _proto_doc_aspect_impl(target, ctx):
     # but just glues together other libs, we just need to follow the graph.
     if not proto_sources:
         return [OutputGroupInfo(rst=transitive_outputs)]
+    # Figure out the set of import paths. Ideally we would use descriptor sets
+    # built by proto_library, which avoid having to do nasty path mangling, but
+    # these don't include source_code_info, which we need for comment
+    # extractions. See https://github.com/bazelbuild/bazel/issues/3971.
+    import_paths = []
+    for f in target.proto.transitive_sources:
+      if f.root.path:
+        import_path = f.root.path + "/" + f.owner.workspace_root
+      else:
+        import_path = f.owner.workspace_root
+      if import_path:
+        import_paths += [import_path]
     # The outputs live in the ctx.label's package root. We add some additional
     # path information to match with protoc's notion of path relative locations.
     outputs = [ctx.actions.declare_file(ctx.label.name + "/" + _proto_path(f) +
@@ -42,18 +54,13 @@ def _proto_doc_aspect_impl(target, ctx):
     # Create the protoc command-line args.
     ctx_path = ctx.label.package + "/" + ctx.label.name
     output_path = outputs[0].root.path + "/" + outputs[0].owner.workspace_root + "/" + ctx_path
-    # proto_library will be generating the descriptor sets for all the .proto deps of the
-    # current node, we can feed them into protoc instead of setting up elaborate -I path
-    # expressions.
-    descriptor_set_in = ":".join([s.path for s in target.proto.transitive_descriptor_sets])
-    args = ["--descriptor_set_in", descriptor_set_in]
+    args = ["-I./" + ctx.label.workspace_root]
+    args += ["-I" + import_path for import_path in import_paths]
     args += ["--plugin=protoc-gen-protodoc=" + ctx.executable._protodoc.path, "--protodoc_out=" + output_path]
     args += [_proto_path(src) for src in target.proto.direct_sources]
     ctx.action(executable=ctx.executable._protoc,
                arguments=args,
-               inputs=[ctx.executable._protodoc] +
-                   target.proto.transitive_descriptor_sets.to_list() +
-                   proto_sources,
+               inputs=[ctx.executable._protodoc] + target.proto.transitive_sources.to_list(),
                outputs=outputs,
                mnemonic="ProtoDoc",
                use_default_shell_env=True)

tools/protodoc/protodoc.py

@@ -1,7 +1,280 @@
+# protoc plugin to map from FileDescriptorProtos to Envoy doc style RST.
+# See https://github.com/google/protobuf/blob/master/src/google/protobuf/descriptor.proto
+# for the underlying protos mentioned in this file.
+
+import functools
 import sys
 
 from google.protobuf.compiler import plugin_pb2
 
+# Namespace prefix for Envoy APIs.
+ENVOY_API_NAMESPACE_PREFIX = '.envoy.api.v2.'
+
+
+class ProtodocError(Exception):
+  """Base error class for the protodoc module."""
+
+
+class SourceCodeInfo(object):
+  """Wrapper for SourceCodeInfo proto."""
+
+  def __init__(self, source_code_info):
+    self._proto = source_code_info
+
+  @property
+  def file_level_comment(self):
+    """Obtain inferred file level comment."""
+    comment = ''
+    earliest_detached_comment = max(
+        max(location.span) for location in self._proto.location)
+    for location in self._proto.location:
+      if location.leading_detached_comments and location.span[0] < earliest_detached_comment:
+        comment = StripLeadingSpace(''.join(
+            location.leading_detached_comments)) + '\n'
+        earliest_detached_comment = location.span[0]
+    return comment
+
+  def LeadingCommentPathLookup(self, path):
+    """Lookup leading comment by path in SourceCodeInfo.
+
+    Args:
+      path: a list of path indexes as per
+        https://github.com/google/protobuf/blob/a08b03d4c00a5793b88b494f672513f6ad46a681/src/google/protobuf/descriptor.proto#L717.
+    Returns:
+      Attached leading comment if it exists, otherwise empty space.
+    """
+    for location in self._proto.location:
+      if location.path == path:
+        return StripLeadingSpace(location.leading_comments) + '\n'
+    return ''
+
+
+def MapLines(f, s):
+  """Apply a function across each line in a flat string.
+
+  Args:
+    f: A string transform function for a line.
+    s: A string consisting of potentially multiple lines.
+  Returns:
+    A flat string with f applied to each line.
+  """
+  return '\n'.join(f(line) for line in s.split('\n'))
+
+
+def Indent(spaces, line):
+  """Indent a string."""
+  return ' ' * spaces + line
+
+
+def IndentLines(spaces, lines):
+  """Indent a list of strings."""
+  return map(functools.partial(Indent, spaces), lines)
+
+
+def FormatHeader(style, text):
+  """Format RST header.
+
+  Args:
+    style: underline style, e.g. '=', '-'.
+    text: header text
+  Returns:
+    RST formatted header.
+  """
+  return '%s\n%s\n\n' % (text, style * len(text))
+
+
+def FormatFieldTypeAsJson(field):
+  """Format FieldDescriptorProto.Type as a pseudo-JSON string.
+
+  Args:
+    field: FieldDescriptor proto.
+  Return:
+    RST formatted pseudo-JSON string representation of field type.
+  """
+  if field.label == field.LABEL_REPEATED:
+    return '[]'
+  if field.type == field.TYPE_MESSAGE:
+    return '"{...}"'
+  return '"..."'
+
+
+def FormatMessageAsJson(msg):
+  """Format a message definition DescriptorProto as a pseudo-JSON block.
+
+  Args:
+    msg: message definition DescriptorProto.
+  Return:
+    RST formatted pseudo-JSON string representation of message definition.
+  """
+  lines = ['"%s": %s' % (f.name, FormatFieldTypeAsJson(f)) for f in msg.field]
+  return '.. code-block:: json\n\n  {\n' + ',\n'.join(IndentLines(
+      4, lines)) + '\n  }\n\n'
+
+
+def NormalizeFQN(fqn):
+  """Normalize a fully qualified field type name.
+
+  Strips leading ENVOY_API_NAMESPACE_PREFIX and makes pretty wrapped type names.
+
+  Args:
+    fqn: a fully qualified type name from FieldDescriptorProto.type_name.
+  Return:
+    Normalized type name.
+  """
+  if fqn.startswith(ENVOY_API_NAMESPACE_PREFIX):
+    return fqn[len(ENVOY_API_NAMESPACE_PREFIX):]
+
+  def Wrapped(s):
+    return '{%s}' % s
+
+  remap_fqn = {
+      '.google.protobuf.UInt32Value': Wrapped('uint32'),
+      '.google.protobuf.UInt64Value': Wrapped('uint64'),
+      '.google.protobuf.BoolValue': Wrapped('bool'),
+  }
+  if fqn in remap_fqn:
+    return remap_fqn[fqn]
+
+  return fqn
+
+
+def FormatEmph(s):
+  """RST format a string for emphasis."""
+  return '*%s*' % s
+
+
+def FormatFieldType(field):
+  """Format a FieldDescriptorProto type description.
+
+  Adds cross-refs for message types.
+  TODO(htuch): Add cross-refs for enums as well.
+
+  Args:
+    field: FieldDescriptor proto.
+  Return:
+    RST formatted field type.
+  """
+  if field.type == field.TYPE_MESSAGE and field.type_name.startswith(
+      ENVOY_API_NAMESPACE_PREFIX):
+    type_name = NormalizeFQN(field.type_name)
+    return ':ref:`%s <%s>`' % (type_name, MessageCrossRefLabel(type_name))
+  # TODO(htuch): Replace with enum handling.
+  if field.type_name:
+    return FormatEmph(NormalizeFQN(field.type_name))
+  pretty_type_names = {
+      field.TYPE_DOUBLE: 'double',
+      field.TYPE_FLOAT: 'float',
+      field.TYPE_INT32: 'int32',
+      field.TYPE_UINT32: 'uint32',
+      field.TYPE_INT64: 'int64',
+      field.TYPE_UINT64: 'uint64',
+      field.TYPE_BOOL: 'bool',
+      field.TYPE_STRING: 'string',
+      field.TYPE_BYTES: 'bytes',
+  }
+  if field.type in pretty_type_names:
+    return FormatEmph(pretty_type_names[field.type])
+  raise ProtodocError('Unknown field type ' + str(field.type))
+
+
+def StripLeadingSpace(s):
+  """Remove leading space in flat comment strings."""
+  return MapLines(lambda s: s[1:], s)
+
+
+def MessageCrossRefLabel(msg_name):
+  """Message cross reference label."""
+  return 'envoy_api_%s' % msg_name
+
+
+def FieldCrossRefLabel(msg_name, field_name):
+  """Field cross reference label."""
+  return 'envoy_api_%s_%s' % (msg_name, field_name)
+
+
+def FormatAnchor(label):
+  """Format a label as an Envoy API RST anchor."""
+  return '.. _%s:\n\n' % label
+
+
+def FormatFieldAsDefinitionListItem(source_code_info, msg, path, field):
+  """Format a FieldDescriptorProto as RST definition list item.
+
+  Args:
+    source_code_info: SourceCodeInfo object.
+    msg: MessageDescriptorProto.
+    path: a list of path indexes as per
+      https://github.com/google/protobuf/blob/a08b03d4c00a5793b88b494f672513f6ad46a681/src/google/protobuf/descriptor.proto#L717.
+    field: FieldDescriptorProto.
+  Returns:
+    RST formatted definition list item.
+  """
+  anchor = FormatAnchor(FieldCrossRefLabel(msg.name, field.name))
+  comment = '(%s) ' % FormatFieldType(
+      field) + source_code_info.LeadingCommentPathLookup(path)
+  return anchor + field.name + '\n' + MapLines(
+      functools.partial(Indent, 2), comment)
+
+
+def FormatMessageAsDefinitionList(source_code_info, path, msg):
+  """Format a MessageDescriptorProto as RST definition list.
+
+  Args:
+    source_code_info: SourceCodeInfo object.
+    path: a list of path indexes as per
+      https://github.com/google/protobuf/blob/a08b03d4c00a5793b88b494f672513f6ad46a681/src/google/protobuf/descriptor.proto#L717.
+    msg: MessageDescriptorProto.
+  Returns:
+    RST formatted definition list item.
+  """
+  return '\n\n'.join(
+      FormatFieldAsDefinitionListItem(source_code_info, msg, path + [2, index],
+                                      field)
+      for index, field in enumerate(msg.field)) + '\n'
+
+
+def FormatMessage(source_code_info, path, msg):
+  """Format a MessageDescriptorProto as RST section.
+
+  Args:
+    source_code_info: SourceCodeInfo object.
+    path: a list of path indexes as per
+      https://github.com/google/protobuf/blob/a08b03d4c00a5793b88b494f672513f6ad46a681/src/google/protobuf/descriptor.proto#L717.
+    msg: MessageDescriptorProto.
+  Returns:
+    RST formatted section.
+  """
+  anchor = FormatAnchor(MessageCrossRefLabel(msg.name))
+  header = FormatHeader('-', msg.name)
+  comment = source_code_info.LeadingCommentPathLookup(path)
+  return anchor + header + comment + FormatMessageAsJson(
+      msg) + FormatMessageAsDefinitionList(source_code_info, path, msg)
+
+
+def FormatProtoAsBlockComment(proto):
+  """Format as RST a proto as a block comment.
+
+  Useful in debugging, not usually referenced.
+  """
+  return '\n\nproto::\n\n' + MapLines(functools.partial(Indent, 2),
+                                      str(proto)) + '\n'
+
+
+def GenerateRst(proto_file):
+  """Generate a RST representation from a FileDescriptor proto.
+
+  """
+  header = FormatHeader('=', proto_file.name)
+  source_code_info = SourceCodeInfo(proto_file.source_code_info)
+  # Find the earliest detached comment, attribute it to file level.
+  comment = source_code_info.file_level_comment
+  msgs = '\n'.join(
+      FormatMessage(source_code_info, [4, index], msg)
+      for index, msg in enumerate(proto_file.message_type))
+  #debug_proto = FormatProtoAsBlockComment(proto_file.source_code_info)
+  return header + comment + msgs  #+ debug_proto
+
+
 if __name__ == '__main__':
   # http://www.expobrain.net/2015/09/13/create-a-plugin-for-google-protocol-buffer/
   request = plugin_pb2.CodeGeneratorRequest()
@@ -13,6 +286,6 @@ if __name__ == '__main__':
     f.name = proto_file.name + '.rst'
     # We don't actually generate any RST right now, we just string dump the
     # input proto file descriptor into the output file.
-    f.content = str(proto_file)
+    f.content = GenerateRst(proto_file)
 
   sys.stdout.write(response.SerializeToString())