support arrays in site options

[parmentelat]

a proposal to implement #2729 (whose focus is now restricted to arrays, not objects)

[changeset-bot]

🦋 Changeset detected

Latest commit: 03a2821

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 4 packages

Name	Type
myst-templates	Minor
myst-cli	Minor
mystmd	Minor
myst-migrate	Minor

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[Copilot]

Pull request overview

Note

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Adds support for template options that accept multiple values via a new multiple flag, including validation/coercion behavior and file-option resolution in site manifests.

Changes:

• Added multiple?: boolean to TemplateOptionDefinition and validated it in option-definition validation.
• Updated validateTemplateOption to support list inputs (and scalar-to-list coercion) when multiple is enabled.
• Updated site manifest file-option resolution to handle file options that validate to a list, plus added tests to cover these behaviors.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
packages/myst-templates/src/validators.ts	Wraps option validation to support multiple via list validation/coercion and validates the multiple flag on definitions.
packages/myst-templates/src/validators.spec.ts	Adds unit tests for multiple option behavior across option validation, options objects, and option definitions.
packages/myst-templates/src/types.ts	Extends TemplateOptionDefinition with a documented multiple flag.
packages/myst-cli/src/build/site/manifest.ts	Resolves/copies file options that may now be arrays (when multiple is enabled).

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[parmentelat]

my recent move is only about rebasing on top of the current main