dev_scripts: pylint: ignore errors per subdir

Add the ability to ignore specific pylint errors on per-subpackage or
per-module basis by adding a plugin that checks the path of the module
against pre-defined sub-paths and inserts disable tags as needed.

dev_scripts/pylint

@@ -42,12 +42,13 @@ if [ "$result" == "2" ]; then
 fi
 
 THIS_DIR="`dirname \"$0\"`"
+CWD=$PWD
+pushd $THIS_DIR > /dev/null
 if [[ "$target" == "" ]]; then
-	pushd $THIS_DIR/.. > /dev/null
 	for dir in "${DEFAULT_DIRS[@]}"; do
-		pylint --rcfile extras/pylintrc $dir
+		PYTHONPATH=. pylint --rcfile ../extras/pylintrc --load-plugins pylint_plugins $CWD/$dir
 	done
-	popd > /dev/null
 else
-	pylint --rcfile $THIS_DIR/../extras/pylintrc $target
+	PYTHONPATH=. pylint --rcfile ../extras/pylintrc --load-plugins pylint_plugins $CWD/$target
 fi
+popd > /dev/null

dev_scripts/pylint_plugins.py

@@ -0,0 +1,45 @@
+from astroid import MANAGER
+from astroid import scoped_nodes
+
+
+IGNORE_ERRORS = {
+        ('attribute-defined-outside-init', ): [
+            'wa.workloads',
+            'wa.instruments',
+            'wa.output_procesors',
+        ]
+}
+
+
+def register(linter):
+    pass
+
+
+def transform(mod):
+    for errors, paths in IGNORE_ERRORS.items():
+        for path in paths:
+            if path in mod.name:
+                text = mod.stream().read()
+                if not text.strip():
+                    return
+
+                text = text.split('\n')
+                # NOTE: doing it this way because the "correct" approach below does not
+                #       work. We can get away with this, because in well-formated WA files,
+                #       the initial line is the copyright header's blank line.
+                if 'pylint:' in text[0]:
+                    msg = 'pylint directive found on the first line of {}; please move to below copyright header'
+                    raise RuntimeError(msg.format(mod.name))
+                if text[0].strip() and text[0][0] != '#':
+                    msg = 'first line of {} is not a comment; is the copyright header missing?'
+                    raise RuntimeError(msg.format(mod.name))
+                text[0] = '# pylint: disable={}'.format(','.join(errors))
+                mod.file_bytes = '\n'.join(text)
+
+                # This is what *should* happen, but doesn't work.
+                # text.insert(0, '# pylint: disable=attribute-defined-outside-init')
+                # mod.file_bytes = '\n'.join(text)
+                # mod.tolineno += 1
+
+
+MANAGER.register_transform(scoped_nodes.Module, transform)