fix(compiler-ssr): support Set model for checkbox/select v-model in SSR

[chatman-media]

Client-side v-model for checkbox and <select multiple> already branches on isArray/isSet/else (see vModelCheckbox and setSelected in runtime-dom/src/directives/vModel.ts), but the SSR codegen in compiler-ssr and the runtime helpers in server-renderer only checked Array.isArray and fell back to treating the model as a plain truthy value otherwise. So a Set model on the server just diverged from the client - worst case, an empty Set rendered every single checkbox as checked, since new Set() is truthy.

Added an isSet branch alongside the existing array check in both the <option>/checkbox codegen and the ssrRenderDynamicModel/ssrGetDynamicModelProps runtime helpers, mirroring the client logic. Added tests covering select-multiple with a Set, checkbox with a Set, and the empty-Set case specifically (including through the dynamic-type and v-bind codepaths) since that's the one that silently does the wrong thing.

Summary by CodeRabbit

• New Features

  • SSR v-model now correctly supports Set values for <select> and checkbox inputs, including multiple selection and dynamic cases.

• Bug Fixes

  • Fixed server-rendered selected and checked states so items in a Set are matched by membership instead of being treated like a single value.
  • Improved consistency for forms using v-model with v-bind and nested option structures.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds Set support to Vue's SSR v-model codegen and runtime. A new ssrIsSet/SSR_IS_SET helper is introduced, wired into compiler-ssr's select/checkbox codegen and server-renderer's checkbox helpers, with corresponding snapshot updates and new tests.

Changes

SSR v-model Set support

Layer / File(s)	Summary
Register SSR_IS_SET runtime helper packages/compiler-ssr/src/runtimeHelpers.ts, packages/server-renderer/src/internal.ts	Adds SSR_IS_SET symbol mapped to ssrIsSet in compiler-ssr helpers and re-exports isSet as ssrIsSet from server-renderer internal exports.
Compiler SSR v-model codegen for Set models packages/compiler-ssr/src/transforms/ssrVModel.ts	Imports createCompoundExpression and SSR_IS_SET; generates .has(value) checks for Set models in select/option selected-state and checkbox checked-state expressions, falling back to prior loose-equality logic otherwise.
Compiler SSR v-model snapshot updates packages/compiler-ssr/__tests__/ssrVModel.spec.ts	Updates inline snapshots across select variants (single, multiple, v-for, v-if, template, optgroup) and checkbox variants to include ssrIsSet import and the new .has(...) branching.
Server-renderer checkbox Set handling packages/server-renderer/src/helpers/ssrVModelHelpers.ts	Adds isSet import and Set-aware .has(value) branches to ssrRenderDynamicModel and ssrGetDynamicModelProps checkbox logic.
Server-renderer Set v-model tests packages/server-renderer/__tests__/ssrDirectives.spec.ts	Adds tests covering select multiple and checkbox v-model with Set models across static, dynamic-type, and v-bind scenarios.

Estimated code review effort: 2 (Simple) | ~15 minutes

Sequence Diagram(s)

Skipped — this PR extends existing branching logic with a new conditional path rather than introducing multi-component sequential interactions.

Suggested labels: scope: ssr, :hammer: p3-minor-bug

Suggested reviewers: sxzz, baiwusanyu-c, yyx990803

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main SSR fix for Set-backed checkbox and select v-model handling.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

🧹 Nitpick comments (1)

packages/server-renderer/src/helpers/ssrVModelHelpers.ts (1)

1-1: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚖️ Poor tradeoff

Consider centralizing the array/set/fallback resolution logic.

The array→set→fallback ternary for checkbox "checked" state is now duplicated across four sites (two here, two in ssrVModel.ts codegen). Not a defect, but a shared runtime helper (e.g. ssrResolveModelChecked(model, value)) could reduce duplication and ease future extension (e.g. additional collection types).

Also applies to: 20-26, 45-51

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@packages/server-renderer/src/helpers/ssrVModelHelpers.ts` at line 1, The
array/set/fallback checked-state resolution logic is duplicated in the v-model
SSR helpers; centralize it into a shared runtime helper such as
ssrResolveModelChecked(model, value) and reuse it from ssrVModelHelpers and the
ssrVModel codegen paths. Update the checkbox checked-state handling in the
existing helper functions (including the branches that currently use isArray,
isSet, looseEqual, and looseIndexOf) to call the shared helper so the behavior
stays identical while reducing duplication and making future collection-type
support easier.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@packages/server-renderer/src/helpers/ssrVModelHelpers.ts`:
- Line 1: The array/set/fallback checked-state resolution logic is duplicated in
the v-model SSR helpers; centralize it into a shared runtime helper such as
ssrResolveModelChecked(model, value) and reuse it from ssrVModelHelpers and the
ssrVModel codegen paths. Update the checkbox checked-state handling in the
existing helper functions (including the branches that currently use isArray,
isSet, looseEqual, and looseIndexOf) to call the shared helper so the behavior
stays identical while reducing duplication and making future collection-type
support easier.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 84e7473b-5832-4811-be12-922469242c57

📥 Commits

Reviewing files that changed from the base of the PR and between c0606e9 and aabbb3a.

📒 Files selected for processing (6)

• packages/compiler-ssr/__tests__/ssrVModel.spec.ts
• packages/compiler-ssr/src/runtimeHelpers.ts
• packages/compiler-ssr/src/transforms/ssrVModel.ts
• packages/server-renderer/__tests__/ssrDirectives.spec.ts
• packages/server-renderer/src/helpers/ssrVModelHelpers.ts
• packages/server-renderer/src/internal.ts