refactor: minor code improvements

src/is-github-alert-type.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, it } from "vitest";
+import { GithubAlertType } from "./github-alert.type.js";
+import { isGithubAlertType } from "./is-github-alert-type.js";
+
+describe("is-github-alert-type", () => {
+  it("should return false for an undefined value", () => {
+    expect(isGithubAlertType(undefined)).toEqual(false);
+  });
+
+  it("should return false for a null value", () => {
+    expect(isGithubAlertType(null)).toEqual(false);
+  });
+
+  it("should return false for a string value not equal to a GitHub alert type", () => {
+    expect(isGithubAlertType("test")).toEqual(false);
+  });
+
+  it("should return true for a value directly taken from the GitHub alert type enum", () => {
+    expect(isGithubAlertType(GithubAlertType.WARNING)).toEqual(true);
+  });
+
+  it("should return true for a string value that equals an alert type", () => {
+    expect(isGithubAlertType("IMPORTANT")).toEqual(true);
+  });
+
+  it("should return false for a string value with the wrong capitalization", () => {
+    expect(isGithubAlertType("important")).toEqual(false);
+  });
+});

src/is-github-alert-type.ts

@@ -0,0 +1,8 @@
+import {
+  GITHUB_ALERT_TYPES,
+  type GithubAlertType,
+} from "./github-alert.type.js";
+
+export function isGithubAlertType(type: unknown): type is GithubAlertType {
+  return GITHUB_ALERT_TYPES.includes(type as GithubAlertType);
+}

src/parse-github-alert-blockquote.test.ts

@@ -4,18 +4,18 @@ import { GithubAlertType } from "./github-alert.type.js";
 import { parseGithubAlertBlockquote } from "./parse-github-alert-blockquote.js";
 
 describe("parse-github-alert-blockquote", () => {
-  it("should return false if the blockquote has no children", () => {
+  it("should return null if the blockquote has no children", () => {
     const blockquote: Blockquote = {
       type: "blockquote",
       children: [],
     };
 
     const result = parseGithubAlertBlockquote(blockquote);
 
-    expect(result).toBe(false);
+    expect(result).toBe(null);
   });
 
-  it("should return false if the first chlid of the blockquote is not a paragraph", () => {
+  it("should return null if the first child of the blockquote is not a paragraph", () => {
     const blockquote: Blockquote = {
       type: "blockquote",
       children: [
@@ -34,10 +34,10 @@ describe("parse-github-alert-blockquote", () => {
 
     const result = parseGithubAlertBlockquote(blockquote);
 
-    expect(result).toBe(false);
+    expect(result).toBe(null);
   });
 
-  it("should return false if the first child of the paragraph is not a text node", () => {
+  it("should return null if the first child of the paragraph is not a text node", () => {
     const blockquote: Blockquote = {
       type: "blockquote",
       children: [
@@ -60,10 +60,10 @@ describe("parse-github-alert-blockquote", () => {
 
     const result = parseGithubAlertBlockquote(blockquote);
 
-    expect(result).toBe(false);
+    expect(result).toBe(null);
   });
 
-  it("should return false if the first paragraph child doesn't contain a valid alert declaration", () => {
+  it("should return null if the first paragraph child doesn't contain a valid alert declaration", () => {
     const blockquote: Blockquote = {
       type: "blockquote",
       children: [
@@ -81,7 +81,7 @@ describe("parse-github-alert-blockquote", () => {
 
     const result = parseGithubAlertBlockquote(blockquote);
 
-    expect(result).toBe(false);
+    expect(result).toBe(null);
   });
 
   it("should return the parsed alert if the blockquote is a valid alert", () => {

src/parse-github-alert-blockquote.ts

@@ -1,32 +1,30 @@
 import type { Blockquote, Paragraph, Text } from "mdast";
 import type { GithubAlert } from "./github-alert.type.js";
-import { parseGithubAlertDeclaration } from "./is-github-alert-declaration.js";
+import { parseGithubAlertDeclaration } from "./parse-github-alert-declaration.js";
 
 /**
  * Function that checks if a given blockquote is a GitHub alert and returns the
  * parsed alert if it is.
  */
 export function parseGithubAlertBlockquote(
   node: Blockquote,
-): false | GithubAlert {
+): GithubAlert | null {
   const [firstChild, ...blockQuoteChildren] = node.children;
 
-  if (firstChild === undefined) return false;
-  if (firstChild.type !== "paragraph") return false;
+  if (firstChild?.type !== "paragraph") return null;
 
   const [firstParagraphChild, ...paragraphChildren] = firstChild.children;
 
-  if (firstParagraphChild === undefined) return false;
-  if (firstParagraphChild.type !== "text") return false;
+  if (firstParagraphChild?.type !== "text") return null;
 
   const [possibleTypeDeclaration, ...textNodes] =
     firstParagraphChild.value.split("\n");
 
-  if (possibleTypeDeclaration === undefined) return false;
+  if (possibleTypeDeclaration === undefined) return null;
 
   const type = parseGithubAlertDeclaration(possibleTypeDeclaration);
 
-  if (type === false) return false;
+  if (type === null) return null;
 
   const textNodeChildren: Text[] =
     textNodes.length > 0 ? [{ type: "text", value: textNodes.join("\n") }] : [];

src/is-github-alert-declaration.test.ts → src/parse-github-alert-declaration.test.ts

@@ -1,19 +1,19 @@
 import { describe, expect, it } from "vitest";
 import { GithubAlertType } from "./github-alert.type.js";
-import { parseGithubAlertDeclaration } from "./is-github-alert-declaration.js";
+import { parseGithubAlertDeclaration } from "./parse-github-alert-declaration.js";
 
-describe("is-github-alert-declaration", () => {
-  it("should return false when passing an empty string.", () => {
+describe("parse-github-alert-declaration", () => {
+  it("should return null when passing an empty string.", () => {
     const result = parseGithubAlertDeclaration("");
-    expect(result).toBe(false);
+    expect(result).toBe(null);
   });
 
-  it("should return false when passing a string that's not a Github alert declaration.", () => {
+  it("should return null when passing a string that is not a Github alert declaration.", () => {
     const resultOne = parseGithubAlertDeclaration("test");
-    expect(resultOne).toBe(false);
+    expect(resultOne).toBe(null);
 
     const resultTwo = parseGithubAlertDeclaration("[!TEST]");
-    expect(resultTwo).toBe(false);
+    expect(resultTwo).toBe(null);
   });
 
   it("should return the alert type when passing a string that is a Github alert declaration.", () => {

src/parse-github-alert-declaration.ts

@@ -0,0 +1,22 @@
+import { type GithubAlertType } from "./github-alert.type.js";
+import { isGithubAlertType } from "./is-github-alert-type.js";
+
+const GITHUB_ALERT_DECLARATION_REGEX = /^\s*\[\!(?<type>\w+)\]\s*$/;
+
+/**
+ * Function that checks if a given string is a GitHub alert declaration and
+ * returns the parsed alert type if it is.
+ *
+ * A GitHub alert declaration is a string that is structured like this:
+ *
+ * `[!TYPE]`
+ */
+export function parseGithubAlertDeclaration(
+  text: string,
+): GithubAlertType | null {
+  const match = text.match(GITHUB_ALERT_DECLARATION_REGEX);
+
+  const type = match?.groups?.type;
+
+  return isGithubAlertType(type) ? type : null;
+}

src/plugin.ts

@@ -13,7 +13,7 @@ export const remarkGithubAdmonitionsToDirectives: Plugin<[], Root> = () => {
       (node: Blockquote, index?: number, parent?: Parent) => {
         const githubAlert = parseGithubAlertBlockquote(node);
 
-        if (githubAlert === false) return;
+        if (githubAlert === null) return;
 
         const directive: ContainerDirective = {
           type: "containerDirective",