Refactor sphinx.environment: Reimplement filter_messages() as a transform

sphinx/environment.py

@@ -728,7 +728,6 @@ class BuildEnvironment(object):
         doctree = pub.document
 
         # post-processing
-        self.filter_messages(doctree)
         self.process_dependencies(docname, doctree)
         self.process_images(docname, doctree)
         self.process_downloads(docname, doctree)
@@ -851,14 +850,6 @@ class BuildEnvironment(object):
 
     # post-processing of read doctrees
 
-    def filter_messages(self, doctree):
-        """Filter system messages from a doctree."""
-        filterlevel = self.config.keep_warnings and 2 or 5
-        for node in doctree.traverse(nodes.system_message):
-            if node['level'] < filterlevel:
-                self.app.debug('%s [filtered system message]', node.astext())
-                node.parent.remove(node)
-
     def process_dependencies(self, docname, doctree):
         """Process docutils-generated dependency info."""
         cwd = getcwd()

sphinx/io.py

@@ -16,7 +16,8 @@ from six import string_types, text_type
 from sphinx.transforms import (
     ApplySourceWorkaround, ExtraTranslatableNodes, PreserveTranslatableMessages, Locale,
     CitationReferences, DefaultSubstitutions, MoveModuleTargets, HandleCodeBlocks,
-    AutoNumbering, AutoIndexUpgrader, SortIds, RemoveTranslatableInline
+    AutoNumbering, AutoIndexUpgrader, SortIds, RemoveTranslatableInline,
+    FilterSystemMessages
 )
 from sphinx.util import import_object, split_docinfo
 
@@ -62,7 +63,7 @@ class SphinxStandaloneReader(SphinxBaseReader):
     transforms = [ApplySourceWorkaround, ExtraTranslatableNodes, PreserveTranslatableMessages,
                   Locale, CitationReferences, DefaultSubstitutions, MoveModuleTargets,
                   HandleCodeBlocks, AutoNumbering, AutoIndexUpgrader, SortIds,
-                  RemoveTranslatableInline, PreserveTranslatableMessages]
+                  RemoveTranslatableInline, PreserveTranslatableMessages, FilterSystemMessages]
 
 
 class SphinxI18nReader(SphinxBaseReader):
@@ -75,7 +76,8 @@ class SphinxI18nReader(SphinxBaseReader):
 
     transforms = [ApplySourceWorkaround, ExtraTranslatableNodes, CitationReferences,
                   DefaultSubstitutions, MoveModuleTargets, HandleCodeBlocks,
-                  AutoNumbering, SortIds, RemoveTranslatableInline]
+                  AutoNumbering, SortIds, RemoveTranslatableInline,
+                  FilterSystemMessages]
 
     def __init__(self, *args, **kwargs):
         SphinxBaseReader.__init__(self, *args, **kwargs)

sphinx/transforms.py

@@ -249,6 +249,19 @@ class PreserveTranslatableMessages(Transform):
             node.preserve_original_messages()
 
 
+class FilterSystemMessages(Transform):
+    """Filter system messages from a doctree."""
+    default_priority = 999
+
+    def apply(self):
+        env = self.document.settings.env
+        filterlevel = env.config.keep_warnings and 2 or 5
+        for node in self.document.traverse(nodes.system_message):
+            if node['level'] < filterlevel:
+                env.app.debug('%s [filtered system message]', node.astext())
+                node.parent.remove(node)
+
+
 class Locale(Transform):
     """
     Replace translatable nodes with their translated doctree.

tests/roots/test-keep_warnings/conf.py

@@ -0,0 +1,4 @@
+# -*- coding: utf-8 -*-
+
+master_doc = 'index'
+keep_warnings = True

tests/roots/test-keep_warnings/index.rst

@@ -0,0 +1,2 @@
+keep_warnings
+=====

tests/test_markup.py

@@ -170,3 +170,21 @@ def test_rst_prolog(app, status, warning):
     # rst_prolog & rst_epilog on exlucding reST parser
     assert not md.rawsource.startswith('*Hello world*.')
     assert not md.rawsource.endswith('*Good-bye world*.\n')
+
+
+@with_app(buildername='dummy', testroot='keep_warnings')
+def test_keep_warnings_is_True(app, status, warning):
+    app.builder.build_all()
+    doctree = pickle.loads((app.doctreedir / 'index.doctree').bytes())
+    assert_node(doctree[0], nodes.section)
+    assert len(doctree[0]) == 2
+    assert_node(doctree[0][1], nodes.system_message)
+
+
+@with_app(buildername='dummy', testroot='keep_warnings',
+          confoverrides={'keep_warnings': False})
+def test_keep_warnings_is_False(app, status, warning):
+    app.builder.build_all()
+    doctree = pickle.loads((app.doctreedir / 'index.doctree').bytes())
+    assert_node(doctree[0], nodes.section)
+    assert len(doctree[0]) == 1