no-switch-case-fall-though: accespt different comment formats (palant…

…ir#2983)

[enhancement] `no-switch-case-fall-through` matches `// falls through` comments case insensitive and allows trailing text

src/rules/noSwitchCaseFallThroughRule.ts

@@ -93,10 +93,7 @@ export class NoSwitchCaseFallThroughWalker extends Lint.AbstractWalker<void> {
 
     private isFallThroughAllowed(clause: ts.CaseOrDefaultClause): boolean {
         const comments = ts.getLeadingCommentRanges(this.sourceFile.text, clause.end);
-        return comments !== undefined && comments.some((comment) => commentText(comment, this.sourceFile).trim() === "falls through");
+        return comments !== undefined &&
+            comments.some((comment) => /^\s*falls through\b/i.test(this.sourceFile.text.slice(comment.pos + 2, comment.end)));
     }
 }
-
-function commentText({ pos, end, kind }: ts.CommentRange, sourceFile: ts.SourceFile): string {
-    return sourceFile.text.slice(pos + 2, kind === ts.SyntaxKind.MultiLineCommentTrivia ? end - 2 : end);
-}

test/rules/no-switch-case-fall-through/test.ts.lint

@@ -125,7 +125,20 @@ switch (foo) {
                 foobar(); // this case clause falls through and returns in the default clause
             default:
             ~~~~~~~    [expected a 'break' before 'default']
-                return; 
+                return;
         }
     case 2:
-}
+}
+
+switch (foo) {
+    case 1:
+        foo;
+        // Falls through
+    case 2:
+        foo;
+        // Falls through.
+    case 3:
+        foo;
+        // Falls through -- for reasons
+    default:
+}