fix: enhance fenced code language rule to support tilde as a delimiter (#344)

* fix: enhance fenced code language rule to support tilde as a delimiter

* wip: improve perf

Author: lumirlumir

src/rules/fenced-code-language.js

@@ -12,6 +12,12 @@
  * FencedCodeLanguageRuleDefinition
  */
 
+//-----------------------------------------------------------------------------
+// Helpers
+//-----------------------------------------------------------------------------
+
+const fencedCodeCharacters = new Set(["`", "~"]);
+
 //-----------------------------------------------------------------------------
 // Rule Definition
 //-----------------------------------------------------------------------------
@@ -58,7 +64,11 @@ export default {
 			code(node) {
 				if (!node.lang) {
 					// only check fenced code blocks
-					if (sourceCode.text[node.position.start.offset] !== "`") {
+					if (
+						!fencedCodeCharacters.has(
+							sourceCode.text[node.position.start.offset],
+						)
+					) {
 						return;
 					}
 

tests/rules/fenced-code-language.test.js

@@ -24,13 +24,22 @@ const ruleTester = new RuleTester({
 
 ruleTester.run("fenced-code-language", rule, {
 	valid: [
+		// backtick code block
 		`\`\`\`js
         console.log("Hello, world!");
         \`\`\``,
 		`\`\`\`javascript
         console.log("Hello, world!");
         \`\`\``,
 
+		// tilde code block
+		`~~~js
+        console.log("Hello, world!");
+        ~~~`,
+		`~~~javascript
+        console.log("Hello, world!");
+        ~~~`,
+
 		// indented code block
 		`
     console.log("Hello, world!");
@@ -57,6 +66,20 @@ ruleTester.run("fenced-code-language", rule, {
 				},
 			],
 		},
+		{
+			code: `~~~
+                console.log("Hello, world!");
+                ~~~`,
+			errors: [
+				{
+					messageId: "missingLanguage",
+					line: 1,
+					column: 1,
+					endLine: 3,
+					endColumn: 20,
+				},
+			],
+		},
 		{
 			code: `\`\`\`javascript
                 console.log("Hello, world!");