Implement the whitespace.suppressor service

This service allows packages to suppress the automatic transformations
of the whitespace package. This is useful for packages that implement or
want to control such functionality themselves.

Fixes atom#160

lib/main.js

@@ -10,5 +10,9 @@ export default {
   deactivate () {
     if (this.whitespace) this.whitespace.destroy()
     this.whitespace = null
+  },
+
+  consumeSuppressor (suppressor) {
+    return this.whitespace.addSuppressor(suppressor)
   }
 }

lib/whitespace.js

@@ -1,11 +1,12 @@
 /** @babel */
 
-import {CompositeDisposable, Point, Range} from 'atom'
+import {Disposable, CompositeDisposable, Point, Range} from 'atom'
 
 const TRAILING_WHITESPACE_REGEX = /[ \t]+(?=\r?$)/g
 
 export default class Whitespace {
   constructor () {
+    this.suppressors = []
     this.subscriptions = new CompositeDisposable()
 
     this.subscriptions.add(atom.workspace.observeTextEditors(editor => {
@@ -70,6 +71,35 @@ export default class Whitespace {
     return this.subscriptions.dispose()
   }
 
+  addSuppressor (suppressor) {
+    this.suppressors.push(suppressor)
+    return new Disposable(() => {
+      this.suppressors.splice(this.suppressors.findIndex(
+        x => x === suppressor
+      ), 1)
+    })
+  }
+
+  shouldSuppressRemoveTrailingWhitespace (editor) {
+    for (let i = 0, n = this.suppressors.length; i < n; i++) {
+      if (this.suppressors[i].shouldSuppressRemoveTrailingWhitespace(editor)) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
+  shouldSuppressEnsureSingleTrailingNewline (editor) {
+    for (let i = 0, n = this.suppressors.length; i < n; i++) {
+      if (this.suppressors[i].shouldSuppressEnsureSingleTrailingNewline(editor)) {
+        return true;
+      }
+    }
+
+    return false;
+  }
+
   handleEvents (editor) {
     let buffer = editor.getBuffer()
 
@@ -79,11 +109,12 @@ export default class Whitespace {
 
         if (atom.config.get('whitespace.removeTrailingWhitespace', {
           scope: scopeDescriptor
-        }) && !this.ignore) {
+        }) && !this.ignore && !this.shouldSuppressRemoveTrailingWhitespace(editor)) {
           this.removeTrailingWhitespace(editor, editor.getGrammar().scopeName)
         }
 
-        if (atom.config.get('whitespace.ensureSingleTrailingNewline', {scope: scopeDescriptor})) {
+        if (atom.config.get('whitespace.ensureSingleTrailingNewline', {scope: scopeDescriptor}) &&
+            !this.shouldSuppressEnsureSingleTrailingNewline(editor)) {
           return this.ensureSingleTrailingNewline(editor)
         }
       })
@@ -102,7 +133,7 @@ export default class Whitespace {
 
       if (atom.config.get('whitespace.removeTrailingWhitespace', {
         scope: scopeDescriptor
-      })) {
+      }) && !this.shouldSuppressRemoveTrailingWhitespace(editor)) {
         if (!atom.config.get('whitespace.ignoreWhitespaceOnlyLines', {
           scope: scopeDescriptor
         })) {

package.json

@@ -40,6 +40,13 @@
       "waitsForPromise"
     ]
   },
+  "consumedServices": {
+    "whitespace.suppressor": {
+      "versions": {
+        "^1.0.0": "consumeSuppressor"
+      }
+    }
+  },
   "configSchema": {
     "removeTrailingWhitespace": {
       "type": "boolean",