Include page path in PageData.vars error messages

lib/build-pages/page-data.js

@@ -137,14 +137,21 @@ export class PageData {
    * @return {T} globalVars, pageVars, and buildVars merged together
    */
   get vars () {
-    if (!this.#initialized) throw new Error('Initialize PageData before accessing vars')
-    const { globalVars, globalDataVars, pageVars, builderVars } = this
-    // @ts-ignore
-    return {
-      ...globalVars,
-      ...globalDataVars,
-      ...pageVars,
-      ...builderVars,
+    if (!this.#initialized) throw new Error(`Initialize PageData before accessing vars for page "${this.pageInfo?.path ?? '<unknown page>'}"`)
+    try {
+      const { globalVars, globalDataVars, pageVars, builderVars } = this
+      // @ts-ignore
+      return {
+        ...globalVars,
+        ...globalDataVars,
+        ...pageVars,
+        ...builderVars,
+      }
+    } catch (err) {
+      throw new Error(
+        `Failed to resolve vars for page "${this.pageInfo.path}": ${err instanceof Error ? err.message : String(err)}`,
+        { cause: err }
+      )
     }
   }
 

lib/build-pages/page-data.test.js

@@ -0,0 +1,53 @@
+import { test } from 'node:test'
+import assert from 'node:assert'
+import { PageData } from './page-data.js'
+
+test.describe('PageData.vars', () => {
+  test('throws with page path before initialization', () => {
+    const pd = new PageData({
+      pageInfo: /** @type {any} */ ({ path: 'blog/test-post' }),
+      globalVars: {},
+      globalStyle: undefined,
+      globalClient: undefined,
+      defaultStyle: null,
+      defaultClient: null,
+      builderOptions: /** @type {any} */ ({}),
+    })
+
+    assert.throws(
+      () => pd.vars,
+      (err) => {
+        assert.ok(err instanceof Error, 'throws an Error')
+        assert.ok(
+          err.message.includes('blog/test-post'),
+          `error message should include the page path, got: "${err.message}"`
+        )
+        return true
+      }
+    )
+  })
+
+  test('error message includes unknown page fallback when pageInfo has no path', () => {
+    const pd = new PageData({
+      pageInfo: /** @type {any} */ ({}),
+      globalVars: {},
+      globalStyle: undefined,
+      globalClient: undefined,
+      defaultStyle: null,
+      defaultClient: null,
+      builderOptions: /** @type {any} */ ({}),
+    })
+
+    assert.throws(
+      () => pd.vars,
+      (err) => {
+        assert.ok(err instanceof Error, 'throws an Error')
+        assert.ok(
+          err.message.includes('<unknown page>'),
+          `error message should include fallback text, got: "${err.message}"`
+        )
+        return true
+      }
+    )
+  })
+})