fix(select): add empty string as option when not required

[Dominik Kadera (dominikkadera)]

Add support for '' to be valid option of non-required selects as it prevents mishaps with JSON Schema alignments.

[Copilot]

Pull request overview

Adds support for using '' as the “no selection” value for non-required select-like fields to better align generated JSON Schema with common form submission semantics, while updating tests and roundtrip behavior accordingly.

Changes:

• Update JSON Schema generation to prepend '' as an allowed option for non-required select-like fields and set default: '' (plus a standard description when none is provided).
• Update validator logic to treat '' as an empty value (and handle placeholder-nested selects with '' as “no selection”).
• Add/adjust Jest test coverage (including a new spec file) for schema generation, validation, and roundtrip behavior.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/forman.ts	Injects empty-string option/default/description for non-required select-like fields; changes placeholder-nested injected option from null to ''.
src/validator.ts	Treats '' as an empty value and extends placeholder-nested select handling to support ''.
src/json.ts	Attempts to prevent roundtrip leakage by filtering out injected '' option and hiding the injected description when converting back to Forman schema.
test/empty-select-option.spec.ts	New tests for schema generation, validation, and roundtrip behavior around optional empty-string select options.
test/placeholder-nested.spec.ts	Updates placeholder-nested schema expectations to use '' and adds validation coverage for empty-string.
test/validator-extended.spec.ts	Updates expectations so optional empty file path '' is treated as valid.
test/test.spec.ts	Updates expected schema fragments to include default: '' and description for optional select-like fields.
test/directives/rpc.spec.ts	Updates expected JSON schema output for RPC-backed selects to include default: '' and description.
test/directives/nested.spec.ts	Updates expected nested directive schemas to include empty option/default/description for non-required select-like fields.
test/directives/grouped.spec.ts	Updates expected grouped select schemas to include empty option/default/description.
test/composites/udttype.spec.ts	Updates expected option count and default for udttype composite select output.
test/composites/__snapshots__/udttype.spec.ts.snap	Snapshot updated for injected empty option/default in udttype output.

Comments suppressed due to low confidence (1)

src/validator.ts:318

• This change makes '' behave like “no value” for all optional fields (not just selects): the validator returns valid: true early and skips type checks and field-level validations (pattern/min/max/etc). If the intent is only to support empty-string for non-required selects (and path-like selectors), consider narrowing this condition to those field types; otherwise, add focused tests that assert the new empty-string semantics for other optional field types with validations.

    if (value == null || value === '') {
        // When a select field has placeholder.nested, null/'' means "no selection" and we need to validate the nested fields
        if (normalizedField.type === 'select' && hasPlaceholderNested(normalizedField)) {
            return handleSelectType(value, normalizedField, context);
        }
        return {
            valid: true,
            errors: [],
        };
    }

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