fix(compiler-ssr): disable v-memo transform in ssr vdom fallback branch #13725

equt · 2025-07-31T08:50:23Z

Summary by CodeRabbit

Bug Fixes
- Prevented memoization logic from being applied during server-side rendering, ensuring correct handling of v-memo directives in SSR.
Tests
- Added a test to verify that slot content with v-memo is rendered correctly in SSR without caching logic.

coderabbitai · 2025-07-31T08:50:31Z

Walkthrough

A condition was added to the memo transform logic to prevent it from running during server-side rendering (SSR). Additionally, a new SSR test was introduced to verify that slot content with v-memo does not generate any cache-related code in SSR output.

Changes

Cohort / File(s)	Change Summary
Memo Transform SSR Guard `packages/compiler-core/src/transforms/vMemo.ts`	Added a check for `context.inSSR` in the `transformMemo` function to skip memo transformation during SSR.
SSR Component Memo Test `packages/compiler-ssr/__tests__/ssrComponent.spec.ts`	Added a test to ensure that slot content with `v-memo` does not produce `_cache` references in SSR output.

Sequence Diagram(s)

sequenceDiagram
    participant Compiler as Compiler
    participant MemoTransform as vMemo Transform

    Compiler->>MemoTransform: transformMemo(node, context)
    MemoTransform->>MemoTransform: Check for memo directive and seen
    MemoTransform->>MemoTransform: Check context.inSSR
    alt inSSR is true
        MemoTransform-->>Compiler: Return early, skip memo transform
    else inSSR is false
        MemoTransform-->>Compiler: Proceed with memo transform
    end

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~7 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Prevent `_cache` references in SSR output for `v-memo` ( #13724 )	✅

Suggested labels

ready to merge, scope: compiler

Poem

A bunny hopped through SSR's night,
Guarding cache from the renderer's sight.
With a check for inSSR,
Memo skipped, no crash by far!
Tests now prove the code is right—
The output clean, the future bright.
🐇✨

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📥 Commits

Reviewing files that changed from the base of the PR and between c875019 and e3d08d8.

📒 Files selected for processing (2)

packages/compiler-core/src/transforms/vMemo.ts (1 hunks)
packages/compiler-ssr/__tests__/ssrComponent.spec.ts (1 hunks)

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GitHub Check: test / e2e-test
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🔇 Additional comments (2)

packages/compiler-core/src/transforms/vMemo.ts (1)

19-19: Perfect fix for the SSR v-memo issue.

The addition of context.inSSR to the early return condition effectively prevents the memo transform from running during server-side rendering, which addresses the core issue where _cache variables are not initialized in SSR context. This targeted approach maintains the existing logic while solving the specific SSR crash problem.

packages/compiler-ssr/__tests__/ssrComponent.spec.ts (1)

320-347: Excellent test coverage for the v-memo SSR fix.

This test case provides comprehensive validation of the fix by:

Verifying that slot content with v-memo compiles without _cache references

Confirming the generated SSR code matches the expected pattern

Following the established testing pattern from the v-once test above

The test effectively validates that the memo transform is properly disabled during SSR compilation, ensuring the fix works as intended.

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github-actions · 2025-07-31T08:51:33Z

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB	38.4 kB	34.6 kB
vue.global.prod.js	159 kB (+10 B)	58.6 kB (+2 B)	52.2 kB (+25 B)

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.6 kB	18.2 kB	16.7 kB
createApp	54.6 kB	21.2 kB	19.4 kB
createSSRApp	58.8 kB	23 kB	20.9 kB
defineCustomElement	59.6 kB	22.8 kB	20.8 kB
overall	68.7 kB	26.4 kB	24.1 kB

pkg-pr-new · 2025-07-31T08:52:01Z

Open in StackBlitz

@vue/compiler-core

npm i https://pkg.pr.new/@vue/compiler-core@13725

@vue/compiler-dom

npm i https://pkg.pr.new/@vue/compiler-dom@13725

@vue/compiler-sfc

npm i https://pkg.pr.new/@vue/compiler-sfc@13725

@vue/compiler-ssr

npm i https://pkg.pr.new/@vue/compiler-ssr@13725

@vue/reactivity

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@vue/runtime-core

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@vue/runtime-dom

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@vue/server-renderer

npm i https://pkg.pr.new/@vue/server-renderer@13725

@vue/shared

npm i https://pkg.pr.new/@vue/shared@13725

vue

npm i https://pkg.pr.new/vue@13725

@vue/compat

npm i https://pkg.pr.new/@vue/compat@13725

commit: e3d08d8

edison1105 · 2025-08-01T00:59:49Z

/ecosystem-ci run

vue-bot · 2025-08-01T01:07:08Z

📝 Ran ecosystem CI: Open

suite	result	latest scheduled
nuxt	✅ success	✅ success
primevue	✅ success	✅ success
pinia	✅ success	✅ success
language-tools	❌ failure	✅ success
test-utils	✅ success	✅ success
vant	✅ success	❌ failure
radix-vue	✅ success	✅ success
router	✅ success	✅ success
vue-i18n	✅ success	✅ success
quasar	✅ success	✅ success
vuetify	✅ success	✅ success
vite-plugin-vue	✅ success	✅ success
vue-simple-compiler	✅ success	✅ success
vitepress	✅ success	✅ success
vueuse	❌ failure	✅ success
vue-macros	❌ failure	❌ failure

fix(compiler-ssr): disable v-memo transform in ssr vdom fallback branch

e3d08d8

edison1105 added ready to merge The PR is ready to be merged. scope: ssr 🔨 p3-minor-bug Priority 3: this fixes a bug, but is an edge case that only affects very specific usage. labels Aug 1, 2025

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