fix: improve cache handling and error recovery

src/core/render/embed.js

@@ -122,7 +122,7 @@ function walkFetchEmbed({ embedTokens, compile, fetch }, cb) {
     };
 
     if (currentToken.embed.url) {
-      get(currentToken.embed.url).then(next);
+      get(currentToken.embed.url).then(next, () => next());
     } else {
       next(currentToken.embed.html);
     }
@@ -133,7 +133,7 @@ function walkFetchEmbed({ embedTokens, compile, fetch }, cb) {
 
 export function prerenderEmbed({ compiler, raw = '', fetch }, done) {
   const hit = cached[raw];
-  if (hit) {
+  if (hit !== undefined) {
     const copy = hit.slice();
     copy.links = hit.links;
     return done(copy);
@@ -205,7 +205,7 @@ export function prerenderEmbed({ compiler, raw = '', fetch }, done) {
   walkFetchEmbed(
     { compile, embedTokens, fetch },
     ({ embedToken, token, rowIndex, cellIndex, tokenRef }) => {
-      if (token) {
+      if (token && embedToken) {
         Object.assign(links, embedToken.links);
 
         if (typeof rowIndex === 'number' && typeof cellIndex === 'number') {
@@ -269,7 +269,7 @@ export function prerenderEmbed({ compiler, raw = '', fetch }, done) {
             });
           }
         }
-      } else {
+      } else if (!token) {
         cached[raw] = tokens.concat();
         tokens.links = cached[raw].links = links;
         done(tokens);

src/core/util/core.js

@@ -10,8 +10,11 @@ export function cached(fn) {
   const cache = Object.create(null);
   return function (str) {
     const key = isPrimitive(str) ? str : JSON.stringify(str);
-    const hit = cache[key];
-    return hit || (cache[key] = fn(str));
+    if (key in cache) {
+      return cache[key];
+    }
+
+    return (cache[key] = fn(str));
   };
 }
 

test/integration/embed.test.js

@@ -262,6 +262,30 @@ Command | Description | Parameters
     expect(mainText).not.toContain("_media/second.md ':include'");
   });
 
+  test('failed embed URL does not block page render', async () => {
+    await docsifyInit({
+      markdown: {
+        homepage: `
+          # Embed Test
+
+          [missing](_media/missing.md ':include')
+
+          Text after missing embed
+
+          [ok](_media/ok.md ':include')
+        `,
+      },
+      routes: {
+        '_media/ok.md': 'reachable include content',
+      },
+    });
+
+    expect(await waitForText('#main', 'Text after missing embed')).toBeTruthy();
+    expect(
+      await waitForText('#main', 'reachable include content'),
+    ).toBeTruthy();
+  });
+
   test('embed file table cell', async () => {
     await docsifyInit({
       markdown: {

test/unit/core-util.test.js

@@ -1,12 +1,38 @@
-import { isExternal } from '../../src/core/util/index.js';
+import { cached, isExternal } from '../../src/core/util/index.js';
 
 // Core util
 // -----------------------------------------------------------------------------
 describe('core/util', () => {
+  describe('cached()', () => {
+    test('memoizes falsy return values', () => {
+      let calls = 0;
+      const fn = cached(() => {
+        calls += 1;
+        return '';
+      });
+
+      expect(fn('same-key')).toBe('');
+      expect(fn('same-key')).toBe('');
+      expect(calls).toBe(1);
+    });
+
+    test('memoizes undefined return values', () => {
+      let calls = 0;
+      const fn = cached(() => {
+        calls += 1;
+        return undefined;
+      });
+
+      expect(fn('same-key')).toBeUndefined();
+      expect(fn('same-key')).toBeUndefined();
+      expect(calls).toBe(1);
+    });
+  });
+
   // isExternal()
   // ---------------------------------------------------------------------------
   describe('isExternal()', () => {
-    // cases non external
+    // cases non-external
     test('non external local url with one /', () => {
       const result = isExternal(`/${location.host}/docsify/demo.md`);