fix(runtime-core): warn about negative number in v-for

[cyrilf]

Context

When using v-for with a negative value, let's say -1, an error occurs in the console:

RangeError: Invalid array length

You can see a reproduction here.

---

Proposed solution

If the number wasn't an integer, we would get a nice warning:

I'm just extending this warning to also includes negative integers.
This way, it's way easier to understand that the issue arises in the v-for and goes into debugging the issue faster.

You can see a reproduction of the fix live here. (the console is correctly warning [Vue warn]: The v-for range expects a positive integer value but got -1. )

---

Side note

• I did a commit for the server-renderer, to stay aligned with the runtime-core change.
  This one was failing silently as it's using a for loop compared to the runtime-core using a new Array(source) where source was -1, hence resulting in the RangeError: Invalid array length error message.

• I did a second commit for the runtime-core package, the one I want to fix.

(actually this issue arised from using the carousel from NuxtUI, but I see that the page / indicators calculation has now been fixed but I still think that this fix is nice to have)

Summary by CodeRabbit

• Bug Fixes

  • Improved validation for list rendering to require a positive integer, preventing negative or non-integer values from being accepted.
  • Updated warning messages to clearly state that a positive integer is expected for list rendering.
  • Ensured that no warnings are issued and no items are rendered when the input is zero.

• Tests

  • Added and updated test cases to cover edge cases for numeric inputs, including negative numbers, zero, and undefined values.

[skirtles-code]

This looks good to me.

Maybe it would be worth adding test cases for 0 too? It feels like something that could easily get broken without tests to catch it.

[cyrilf]

We could add test cases for 0 but I believe that currently everything behave correctly with 0.
If I give an empty array, I'm used to the fact that the v-for isn't going to render anything. And I don't expect a warning either (similar to a for loop on an empty array).
Maybe you meant adding tests but not necessarily as errors?

[skirtles-code]

Yes, I meant adding tests to confirm that 0 renders nothing, without a warning or error.

Your code contains a boundary condition of source < 0. Currently you've tested one side of that boundary, with a test for -1, but not the other side. The current tests would pass if the code were changed to source <= 0, or source < 1, or even source < 3. The tests should ideally lock it down exactly, so no future mistakes can be introduced.

[coderabbitai]

Walkthrough

Validation logic for numeric sources in both renderList and ssrRenderList was updated to require positive integers. Warning messages were revised to reflect this requirement. Test suites were expanded to cover cases involving zero, negative, and undefined numeric inputs, ensuring correct warnings and behavior for these edge cases.

Changes

File(s)	Change Summary
packages/runtime-core/src/helpers/renderList.ts, packages/server-renderer/src/helpers/ssrRenderList.ts	Enhanced numeric validation to require positive integers; updated warning messages accordingly.
packages/runtime-core/__tests__/helpers/renderList.spec.ts, packages/server-renderer/__tests__/ssrRenderList.spec.ts	Added and updated tests for zero, negative, and undefined numeric inputs; verified new warning logic.

Sequence Diagram(s)

sequenceDiagram
    participant Caller
    participant renderList/ssrRenderList

    Caller->>renderList/ssrRenderList: Call with source (number)
    alt source is not a positive integer
        renderList/ssrRenderList->>Caller: Warn "expects a positive integer value"
        renderList/ssrRenderList->>Caller: Return empty list
    else source is a positive integer
        renderList/ssrRenderList->>Caller: Return generated list
    end

Loading

Estimated code review effort

2 (~20 minutes)

Poem

In the warren where numbers hop and play,
Only positive integers may join the array.
If you bring a negative, undefined, or a float,
A warning is issued—no need to emote!
Zero brings silence, with no list to show,
The rabbits have spoken: now onward we go! 🐇

---

📜 Recent review details

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📥 Commits

Reviewing files that changed from the base of the PR and between 5082822 and 28c5ecb.

📒 Files selected for processing (4)

• packages/runtime-core/__tests__/helpers/renderList.spec.ts (2 hunks)
• packages/runtime-core/src/helpers/renderList.ts (1 hunks)
• packages/server-renderer/__tests__/ssrRenderList.spec.ts (2 hunks)
• packages/server-renderer/src/helpers/ssrRenderList.ts (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (4)

• packages/runtime-core/src/helpers/renderList.ts
• packages/server-renderer/src/helpers/ssrRenderList.ts
• packages/server-renderer/tests/ssrRenderList.spec.ts
• packages/runtime-core/tests/helpers/renderList.spec.ts

✨ Finishing Touches

• 📝 Generate Docstrings

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[cyrilf]

Got it!
Thanks for taking the time to clarify, I appreciate it.

I've updated the tests accordingly and pushed my changes.

[skirtles-code]

Looks good to me.

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	101 kB	38.3 kB	34.5 kB
vue.global.prod.js	159 kB	58.5 kB	52 kB

Usages

Name	Size	Gzip	Brotli
createApp (CAPI only)	46.5 kB	18.2 kB	16.7 kB
createApp	54.5 kB	21.2 kB	19.4 kB
createSSRApp	58.7 kB	22.9 kB	20.9 kB
defineCustomElement	59.4 kB	22.8 kB	20.8 kB
overall	68.5 kB	26.4 kB	24 kB

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commit: 5082822