fix(runtime-core): allow an empty dynamic component (fix #3632)

[JonathanYin]

closes #3632

<component :is="''"> warned about an invalid type, though it already
renders nothing, the same as :is="null".

Summary by CodeRabbit

• Bug Fixes
  • Fixed dynamic component resolution for empty or falsy component values.
  • These values now render as empty placeholder content without triggering unnecessary warnings or lookup errors.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: b0821b09-945f-4fd3-8b2d-e50886390fa0

📥 Commits

Reviewing files that changed from the base of the PR and between 5be58b4 and 860bb9b.

📒 Files selected for processing (2)

• packages/runtime-core/__tests__/helpers/resolveAssets.spec.ts
• packages/runtime-core/src/helpers/resolveAssets.ts

Included review availability: Your plan provides up to 10 included reviews per hour; 8 remain after this review.

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📝 Walkthrough

Walkthrough

resolveDynamicComponent now treats an empty string as falsy. The test verifies that it produces a Comment vnode without a warning.

Changes

Dynamic component resolution

Layer / File(s)	Summary
Resolver guard and regression test packages/runtime-core/src/helpers/resolveAssets.ts, packages/runtime-core/__tests__/helpers/resolveAssets.spec.ts	The resolver skips asset lookup for falsy component values. The test verifies that an empty string resolves to a Comment vnode.

Priority: ➖ Normal

Estimated code review effort: 1 (Trivial) | ~5 minutes

Change: Bug fix · Severity of issue fixed: Medium

Merge Risk: ⚪ Minimal · up to 860bb

Empty dynamic components now render as comments without the prior invalid-type behavior; no actionable merge risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 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 change: allowing an empty dynamic component in runtime-core. It also identifies the related issue.
Linked Issues check	✅ Passed	The change satisfies #3632. resolveDynamicComponent now treats an empty string as a falsy dynamic component and returns NULL_DYNAMIC_COMPONENT, like null. The new test creates a vnode from `reso…
Out of Scope Changes check	✅ Passed	The changes stay within #3632. They modify dynamic-component resolution and add a focused regression test for the empty-string case. No unrelated behavior or files are changed.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create a new PR

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