feat(core-eslint): component-must-have-story rule

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/core-eslint/rules/component-must-have-story.js

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+import fs from "node:fs";
+import path from "node:path";
+
+/**
+ * Identifies "component files" by location + extension:
+ * - `.tsx` extension
+ * - Inside `packages/core-ui/src/` OR `packages/<feature>/src/ui/`
+ * - NOT a test, stories, spec, or barrel file
+ */
+function isComponentFile(filename) {
+  if (!filename.endsWith(".tsx")) return false;
+  const base = path.basename(filename);
+  if (
+    base === "index.tsx" ||
+    base.endsWith(".test.tsx") ||
+    base.endsWith(".stories.tsx") ||
+    base.endsWith(".spec.tsx")
+  ) {
+    return false;
+  }
+  return (
+    filename.includes("/packages/core-ui/src/") ||
+    /\/packages\/[^/]+\/src\/ui\//.test(filename)
+  );
+}
+
+/** @type {import("eslint").Rule.RuleModule} */
+export default {
+  meta: {
+    type: "problem",
+    docs: {
+      description:
+        "Every component file must have a sibling *.stories.tsx for Storybook coverage.",
+    },
+    schema: [],
+    messages: {
+      missingStory:
+        "Component {{filename}} has no sibling Storybook story at {{expected}}. Stories are the spec for visual conformance.",
+    },
+  },
+  create(context) {
+    return {
+      Program(node) {
+        const filename = context.filename;
+        if (!isComponentFile(filename)) return;
+        const expected = filename.replace(/\.tsx$/, ".stories.tsx");
+        if (fs.existsSync(expected)) return;
+        context.report({
+          node,
+          messageId: "missingStory",
+          data: {
+            filename: path.basename(filename),
+            expected: path.basename(expected),
+          },
+        });
+      },
+    };
+  },
+};

packages/core-eslint/rules/component-must-have-story.test.js

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+import { describe, it } from "vitest";
+import { RuleTester } from "eslint";
+import path from "node:path";
+import os from "node:os";
+import fs from "node:fs";
+import rule from "./component-must-have-story.js";
+
+function makeFixture({ withStory, location = "core-ui" }) {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), "cmhs-"));
+  const dir =
+    location === "core-ui"
+      ? path.join(root, "packages", "core-ui", "src", "atoms", "Button")
+      : path.join(root, "packages", "demo", "src", "ui", "atoms", "Button");
+  fs.mkdirSync(dir, { recursive: true });
+  const component = path.join(dir, "Button.tsx");
+  fs.writeFileSync(component, `export const Button = () => <button>x</button>;`);
+  if (withStory) {
+    fs.writeFileSync(path.join(dir, "Button.stories.tsx"), `export default { title: "Button" };`);
+  }
+  return { component };
+}
+
+const tester = new RuleTester({
+  languageOptions: {
+    parser: await import("@typescript-eslint/parser"),
+    ecmaVersion: "latest",
+    sourceType: "module",
+    parserOptions: { ecmaFeatures: { jsx: true } },
+  },
+});
+
+describe("component-must-have-story", () => {
+  it("passes for a core-ui component with a sibling .stories.tsx", () => {
+    const { component } = makeFixture({ withStory: true });
+    tester.run("component-must-have-story", rule, {
+      valid: [{ filename: component, code: fs.readFileSync(component, "utf8") }],
+      invalid: [],
+    });
+  });
+
+  it("fires for a core-ui component without a sibling .stories.tsx", () => {
+    const { component } = makeFixture({ withStory: false });
+    tester.run("component-must-have-story", rule, {
+      valid: [],
+      invalid: [{
+        filename: component,
+        code: fs.readFileSync(component, "utf8"),
+        errors: [{ messageId: "missingStory" }],
+      }],
+    });
+  });
+
+  it("passes for a feature ui component with a sibling .stories.tsx", () => {
+    const { component } = makeFixture({ withStory: true, location: "feature" });
+    tester.run("component-must-have-story", rule, {
+      valid: [{ filename: component, code: fs.readFileSync(component, "utf8") }],
+      invalid: [],
+    });
+  });
+
+  it("is a no-op for index.tsx", () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), "cmhs-"));
+    const dir = path.join(root, "packages", "core-ui", "src", "atoms", "Button");
+    fs.mkdirSync(dir, { recursive: true });
+    const file = path.join(dir, "index.tsx");
+    fs.writeFileSync(file, `export * from "./Button";`);
+    tester.run("component-must-have-story", rule, {
+      valid: [{ filename: file, code: fs.readFileSync(file, "utf8") }],
+      invalid: [],
+    });
+  });
+
+  it("is a no-op for files outside packages/core-ui/ and packages/*/src/ui/", () => {
+    const root = fs.mkdtempSync(path.join(os.tmpdir(), "cmhs-"));
+    const dir = path.join(root, "packages", "auth", "src", "application", "use-cases");
+    fs.mkdirSync(dir, { recursive: true });
+    const file = path.join(dir, "sign-in.use-case.tsx");
+    fs.writeFileSync(file, `export const x = 1;`);
+    tester.run("component-must-have-story", rule, {
+      valid: [{ filename: file, code: fs.readFileSync(file, "utf8") }],
+      invalid: [],
+    });
+  });
+});