fix: clear form issues when error() is used after validation passes

[Copilot]

Problem

When a remote form is submitted with invalid values, validation issues are displayed. If the form is then resubmitted with valid values but the handler calls error() (e.g., for authentication), the validation issues remain visible even though validation passed.

<form {...createPost.enhance(async ({ submit }) => {
  try {
    await submit()
  } catch (error) {
    console.log('error occurred')
  }
})}>
  <input {...createPost.fields.title.as('text')}>
  {#if createPost.fields.title.issues()}
    <!-- These issues don't clear when validation passes but error() is thrown -->
    <p>{createPost.fields.title.issues()!.at(0)!.message}</p>
  {/if}
</form>

export const createPost = form(
  object({
    title: pipe(string(), nonEmpty())
  }),
  async (data) => {
    const currentUser = await getCurrentUser()
    if (!currentUser) {
      error(401) // Validation passed, but issues aren't cleared on client
    }
    // proceed
  }
)

Solution

The client had no way to know that validation passed when an error was thrown. The fix ensures validation state is communicated even when errors occur:

1. Server: Set output.issues = {} when validation passes (before calling user handler)
2. Server: Always cache the output so validation state is preserved even if an error is thrown
3. Server: Include cached issues in error response when available
4. Client: Parse issues from error response; if empty (validation passed), clear old issues before throwing the error

Changes

• packages/kit/src/runtime/app/server/remote/form.js: Set and cache empty issues when validation passes
• packages/kit/src/runtime/server/remote.js: Include issues from cache in form error responses
• packages/kit/src/runtime/client/remote-functions/form.svelte.js: Clear issues when error response indicates validation passed
• packages/kit/src/types/internal.d.ts: Add optional issues field to ServerErrorNode type
• Added test case to verify issues are cleared when valid data triggers an error

Fixes #[issue_number]

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Original prompt

---

This section details on the original issue you should resolve

<issue_title>Valid field issues are not cleared when error is used in remote form handler</issue_title>
<issue_description>### Describe the problem

1. Submit form with intentionally invalid values
2. Invalid fields will have issues
3. Submit form again but make sure it's valid
4. If error is used inside form, fields issues are not updated even though validation passes

Enhanced form:

<form {...createPost.enhance(async ({ submit }) => {
  try {
    await submit()
  } catch (error) {
    console.log('oh wow, we have an error')
  }
})}>
  <input {...createPost.fields.title.as('text')}>
  {#if createPost.fields.title.issues()}
    <p>{createPost.fields.title.issues()!.at(0)!.message}</p>
  {/if}
</form>

Remote form:

export const createPost = form(
  object({
    title: pipe(string(), nonEmpty())
  }),
  async (data) => {
    const currentUser = await getCurrentUser()

    if (!currentUser) {
      return error(401)
    }

    // proceed
  }
)

Describe the proposed solution

Field issues should be updated even with error since validation passes and handler is executed

Alternatives considered

Current workaround is to manually validate in catch:

<form {...createPost.enhance(async ({ submit }) => {
  try {
    await submit()
  } catch (error) {
    await createPost.validate({ includeUntouched: true })
  }
})}>

Importance

would make my life easier

Additional Information

@sveltejs/kit - 2.46.1
svelte - 5.39.9
</issue_description>

<agent_instructions>look into form.js and form.svelte.js to fix the bug. add a test to the test/apps/basic app at src/routes/remote/form/validate by enhancing my_form in form.remote.ts to error(...) in case of a specific value set to then test that the issues are cleared.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #14646

---

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[changeset-bot]

⚠️ No Changeset found

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[svelte-docs-bot]

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[dummdidumm]

useless