chore(doc-gen): report on missing or obsolete error docs

Closes angular#12527

Author: Narretz

docs/config/processors/error-docs.js

@@ -5,18 +5,36 @@
  * @description
  * Process "error" docType docs and generate errorNamespace docs
  */
-module.exports = function errorDocsProcessor(errorNamespaceMap, getMinerrInfo) {
+module.exports = function errorDocsProcessor(log, errorNamespaceMap, getMinerrInfo) {
   return {
     $runAfter: ['tags-extracted'],
     $runBefore: ['extra-docs-added'],
     $process: function(docs) {
 
+      // Get the extracted min errors to compare with the error docs, and report any mismatch
+      var collectedErrors = require('../../../build/errors.json').errors;
+      var flatErrors = [];
+
+      for (var namespace in collectedErrors) {
+        for (var error in collectedErrors[namespace]) {
+          flatErrors.push(namespace + ':' + error);
+        }
+      }
+
       // Create error namespace docs and attach error docs to each
       docs.forEach(function(doc) {
         var parts, namespaceDoc;
 
         if (doc.docType === 'error') {
 
+          var matchingMinErr = flatErrors.indexOf(doc.name);
+
+          if (matchingMinErr === -1) {
+            log.warn('Error doc: ' + doc.name + ' has no matching min error');
+          } else {
+            flatErrors.splice(matchingMinErr, 1);
+          }
+
           // Parse out the error info from the id
           parts = doc.name.split(':');
           doc.namespace = parts[0];
@@ -41,6 +59,10 @@ module.exports = function errorDocsProcessor(errorNamespaceMap, getMinerrInfo) {
         }
       });
 
+      flatErrors.forEach(function(value) {
+        log.warn('No error doc exists for min error: ' + value);
+      });
+
       errorNamespaceMap.forEach(function(errorNamespace) {
         docs.push(errorNamespace);
       });