fix(schema): emit enum default values as enum values, not strings - #525
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value() checked `val instanceof Symbol` to decide whether to emit Kind.ENUM.
Symbols are primitives, so that is never true — the branch was unreachable and
there was no way to express an enum default at all.
Enum defaults passed as plain strings therefore fell into the STRING branch and
printed as `mutationMode: MutationMode = "STRICT"`. That is an invalid default
value for an enum: graphql 16 tolerated it, graphql 17 rejects it with
'Enum "X" cannot represent non-enum value', which blocks schema generation
entirely on graphql 17.
Fix the check to `typeof val === 'symbol'` so `defaultValue: Symbol('STRICT')`
prints as `= STRICT`. Value is already `unknown`, so no type change is needed,
and nothing can depend on the old behaviour because the branch never ran.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
nicola-smartive
marked this pull request as ready for review
July 16, 2026 17:00
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The bug
value()insrc/schema/utils.tsdecides whether to emitKind.ENUMwith:Symbols are primitives, so
Symbol('X') instanceof Symbolis alwaysfalse. That branch has never been reachable — meaning there is currently no way to express an enum default value at all.So an enum default written the natural way,
defaultValue: 'STRICT', falls into thetypeof val === 'string'branch above and prints as:That is an invalid default for an enum. graphql 16 tolerated it; graphql 17 rejects it:
Which means schema generation fails outright on graphql 17 — a hard blocker for consumers upgrading. Found while triaging a graphql 17 bump in zwei-wealth-platform.
Worth noting the SDL we emit today is already invalid; graphql 16's leniency is the only thing hiding it. So this is a correctness fix independent of 17.
The fix
One line —
typeof val === 'symbol'— restoring the branch's evident intent.Valueis alreadyunknown, soSymbol('STRICT')is accepted.defaultValue: Symbol('STRICT')→ prints= STRICT.Tests
Added
tests/unit/enum-default-values.spec.tscovering enum-vs-string and symbols-in-lists. Verified it genuinely catches the bug: reverting the one-line fix turns it 2 failed / 1 passed, restoring it 3 passed. Full unit suite green (132 tests), lint clean.Possible follow-up (deliberately not in this PR)
A string default on an enum-typed field still silently produces invalid SDL. Making
value()type-aware (emitKind.ENUMwhen the field's type is an enum) would remove the footgun entirely, but needs the enum registry threaded into the generic AST builders — a design call for the maintainers rather than something to smuggle into a bug fix.