Remove dependencies on Linguist

This saves about 128 MB of baseline RAM usage per Unicorn and
Sidekiq process (!).

Linguist wasn't detecting languages anymore from CE/EE since
9ae8b57467ac8b38f1fa9020a466d94a93cbb9dd. However, Linguist::BlobHelper
was still being depended on by BlobLike and others.

This removes the Linguist gem, given it isn't required anymore.
EscapeUtils were pulled in as dependency, but given Banzai depends on
it, it is now added explicitly.

Previously, Linguist was used to detect the best ACE mode. Instead,
we rely on ACE to guess the best mode based on the file extension.

8 files changed, 19 insertions, 9 deletions

diff --git a/app/assets/javascripts/blob_edit/blob_bundle.js b/app/assets/javascripts/blob_edit/blob_bundle.js
index 4e4598870fa..3cc89ff1955 100644
--- a/app/assets/javascripts/blob_edit/blob_bundle.js
+++ b/app/assets/javascripts/blob_edit/blob_bundle.js
@@ -13,11 +13,11 @@ export default () => {
   if (editBlobForm.length) {
     const urlRoot = editBlobForm.data('relativeUrlRoot');
     const assetsPath = editBlobForm.data('assetsPrefix');
-    const blobLanguage = editBlobForm.data('blobLanguage');
+    const filePath = editBlobForm.data('blobFilename')
     const currentAction = $('.js-file-title').data('currentAction');
     const projectId = editBlobForm.data('project-id');
 
-    new EditBlob(`${urlRoot}${assetsPath}`, blobLanguage, currentAction, projectId);
+    new EditBlob(`${urlRoot}${assetsPath}`, filePath, currentAction, projectId);
     new NewCommitForm(editBlobForm);
   }
 
diff --git a/app/assets/javascripts/blob_edit/edit_blob.js b/app/assets/javascripts/blob_edit/edit_blob.js
index ec2b130ab7d..6e19548eed2 100644
--- a/app/assets/javascripts/blob_edit/edit_blob.js
+++ b/app/assets/javascripts/blob_edit/edit_blob.js
@@ -5,6 +5,7 @@ import axios from '~/lib/utils/axios_utils';
 import createFlash from '~/flash';
 import { __ } from '~/locale';
 import TemplateSelectorMediator from '../blob/file_template_mediator';
+import getModeByFileExtension from '~/lib/utils/ace_utils';
 
 export default class EditBlob {
   constructor(assetsPath, aceMode, currentAction, projectId) {
@@ -14,9 +15,10 @@ export default class EditBlob {
     this.initFileSelectors(currentAction, projectId);
   }
 
-  configureAceEditor(aceMode, assetsPath) {
+  configureAceEditor(filePath, assetsPath) {
     ace.config.set('modePath', `${assetsPath}/ace`);
     ace.config.loadModule('ace/ext/searchbox');
+    ace.config.loadModule('ace/ext/modelist');
 
     this.editor = ace.edit('editor');
 
@@ -25,8 +27,8 @@ export default class EditBlob {
 
     this.editor.focus();
 
-    if (aceMode) {
-      this.editor.getSession().setMode(`ace/mode/${aceMode}`);
+    if (filePath) {
+      this.editor.getSession().setMode(getModeByFileExtension(filePath));
     }
   }
 
diff --git a/app/assets/javascripts/lib/ace.js b/app/assets/javascripts/lib/ace.js
index 9cdc0309503..e90b3d2eec7 100644
--- a/app/assets/javascripts/lib/ace.js
+++ b/app/assets/javascripts/lib/ace.js
@@ -1,3 +1,4 @@
 /*= require ace/ace */
+/*= require ace/ext-modelist */
 /*= require ace/ext-searchbox */
 /*= require ./ace/ace_config_paths */
diff --git a/app/assets/javascripts/lib/utils/ace_utils.js b/app/assets/javascripts/lib/utils/ace_utils.js
new file mode 100644
index 00000000000..efc4b2a8d94
--- /dev/null
+++ b/app/assets/javascripts/lib/utils/ace_utils.js
@@ -0,0 +1,6 @@
+/* global ace */
+
+export default function getModeByFileExtension(path) {
+  const modelist = ace.require("ace/ext/modelist");
+  return modelist.getModeForPath(path).mode;
+};
diff --git a/app/assets/javascripts/merge_conflicts/components/diff_file_editor.js b/app/assets/javascripts/merge_conflicts/components/diff_file_editor.js
index 425b806e9d6..a62ebe23646 100644
--- a/app/assets/javascripts/merge_conflicts/components/diff_file_editor.js
+++ b/app/assets/javascripts/merge_conflicts/components/diff_file_editor.js
@@ -5,6 +5,7 @@ import Vue from 'vue';
 import axios from '~/lib/utils/axios_utils';
 import flash from '~/flash';
 import { __ } from '~/locale';
+import getModeByFileExtension from '~/lib/utils/ace_utils';
 
 (global => {
   global.mergeConflicts = global.mergeConflicts || {};
@@ -72,7 +73,7 @@ import { __ } from '~/locale';
             this.fileLoaded = true;
             this.editor = ace.edit(content);
             this.editor.$blockScrolling = Infinity; // Turn off annoying warning
-            this.editor.getSession().setMode(`ace/mode/${data.blob_ace_mode}`);
+            this.editor.getSession().setMode(getModeByFileExtension(data.new_path));
             this.editor.on('change', () => {
               this.saveDiffResolution();
             });
diff --git a/app/helpers/blob_helper.rb b/app/helpers/blob_helper.rb
index 883e5ddff57..8d58c86b7a4 100644
--- a/app/helpers/blob_helper.rb
+++ b/app/helpers/blob_helper.rb
@@ -195,7 +195,7 @@ module BlobHelper
     {
       'relative-url-root' => Rails.application.config.relative_url_root,
       'assets-prefix' => Gitlab::Application.config.assets.prefix,
-      'blob-language' => @blob && @blob.language.try(:ace_mode),
+      'blob-filename' => @blob && @blob.path,
       'project-id' => project.id
     }
   end
diff --git a/app/models/blob.rb b/app/models/blob.rb
index acc64ffca67..31a839274b5 100644
--- a/app/models/blob.rb
+++ b/app/models/blob.rb
@@ -162,7 +162,7 @@ class Blob < SimpleDelegator
     if stored_externally?
       if rich_viewer
         rich_viewer.binary?
-      elsif Linguist::Language.find_by_extension(name).any?
+      elsif known_extension?
         false
       elsif _mime_type
         _mime_type.binary?
diff --git a/app/models/concerns/blob_like.rb b/app/models/concerns/blob_like.rb
index e96fefe81c4..f20f01486a5 100644
--- a/app/models/concerns/blob_like.rb
+++ b/app/models/concerns/blob_like.rb
@@ -2,7 +2,7 @@
 
 module BlobLike
   extend ActiveSupport::Concern
-  include Linguist::BlobHelper
+  include Gitlab::BlobHelper
 
   def id
     raise NotImplementedError