Handle editor contents changing

If the editor contents have been changed since the lint was triggered
the results returned are no longer valid. If this has happend tell
Linter not to update the current message set for the provider as any
current messages will have "followed" the text if possible.

Author: Arcanemagus

lib/main.js

@@ -63,7 +63,7 @@ export default {
       scope: 'file',
       lintOnFly: false,
       grammarScopes: ['source.c', 'source.cpp', 'source.objc', 'source.objcpp'],
-      lint: (editor) => {
+      lint: async (editor) => {
         if (helpers === null) {
           helpers = require('atom-linter');
         }
@@ -72,6 +72,7 @@ export default {
         }
 
         const filePath = editor.getPath();
+        const fileText = editor.getText();
 
         const args = [
           '-fsyntax-only',
@@ -136,9 +137,16 @@ export default {
           allowEmptyStderr: true,
         };
 
-        return helpers.exec(this.execPath, args, execOpts).then(output =>
-          helpers.parse(output, regex),
-        );
+        const output = await helpers.exec(this.execPath, args, execOpts);
+
+        if (editor.getText() !== fileText) {
+          // Editor contents have changed, tell Linter not to update results
+          // eslint-disable-next-line no-console
+          console.warn('linter-clang: Editor contents changed, not updating results');
+          return null;
+        }
+
+        return helpers.parse(output, regex);
       },
     };
   },