[libgraphql-core-v1] Task 15: Validators (object/interface, union, input object, directive)

[jeffmo]

Summary

Implements 4 type-system validators for cross-type validation of GraphQL schemas. These validators are designed to be called from SchemaBuilder::build() (Task 16) but are not yet wired into the build pipeline — build() is currently todo!().

ObjectOrInterfaceTypeValidator

• Generic over T: HasFieldsAndInterfaces — validates both ObjectType and InterfaceType
• Three-phase interface validation: (1) completeness — implemented interfaces exist and are interface types, (2) field contracts — all interface fields present with compatible params, additional params must be optional, (3) field types — covariant return types
• Precise error spans: interface-clause errors point at the interface reference span, not the whole type
• Rich error notes: param type mismatches, required additional params, and return type mismatches all include notes pointing at the interface's definition
• Output field types must be output types, param types must be input types
• Edit-distance "did you mean?" suggestions on undefined-name errors

UnionTypeValidator

• Members must exist in types_map and be Object types
• Edit-distance "did you mean?" suggestions on undefined member names
• Empty union check (EmptyUnionType) is a SchemaBuildErrorKind — will be added in build() (Task 16)

InputObjectTypeValidator

• Fixed v0 bug: uses !is_input_type() instead of as_object().is_some() — now correctly rejects Interface and Union types as input field types
• Circular non-nullable reference detection via recursive DFS; list types break circular chains per spec
• Edit-distance "did you mean?" suggestions on undefined type references

DirectiveDefinitionValidator (NEW — absent in v0)

• Validates custom directive parameter types are input types
• Dedicated InvalidDirectiveParameterType error variant
• Edit-distance "did you mean?" suggestions on undefined parameter type references

Removed: type_reference_validator

All type reference validation is distributed across the per-type validators — no separate pass needed.

Cross-cutting

• All identifiers in error messages wrapped in backticks
• All error pushes include spec-link notes
• Precise spans: interface-clause errors use the interface reference span
• Edit-distance "did you mean?" suggestions on all undefined-name errors

Note: Validators are not yet wired into SchemaBuilder::build() — that is Task 16.

Test plan

• 194 total tests pass (cargo test --package libgraphql-core-v1)
• Validator tests cover all error paths: undefined types, wrong type kinds, missing fields, param mismatches, return type covariance, circular input objects, directive param types
• cargo clippy --tests --package libgraphql-core-v1 -- -D warnings clean
• cargo check --tests --package libgraphql-core-v1 clean

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Implements cross-type schema validation in libgraphql-core-v1 during SchemaBuilder::build(), adding per-type validators for object/interface implementation rules, unions, input objects, and directive definitions.

Changes:

• Added 4 validators (object/interface, union, input object, directive definition) plus comprehensive unit tests.
• Updated type-validation error display formatting for circular input field chains (wrapping identifiers in backticks).
• Exposed a new internal validators module and updated the implementation plan notes.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
libgraphql-core-v1-plan.md	Marks validator work as completed and documents implementation notes.
crates/libgraphql-core-v1/src/lib.rs	Adds internal validators module to the crate.
crates/libgraphql-core-v1/src/validators/mod.rs	Declares validator submodules and re-exports validator entry points.
crates/libgraphql-core-v1/src/validators/object_or_interface_type_validator.rs	Validates interface implementation correctness and input/output type legality for fields/params.
crates/libgraphql-core-v1/src/validators/union_type_validator.rs	Validates union member existence and member type-kind constraints.
crates/libgraphql-core-v1/src/validators/input_object_type_validator.rs	Validates input field types and detects non-nullable circular input object reference chains.
crates/libgraphql-core-v1/src/validators/directive_definition_validator.rs	Validates custom directive parameter types are input types.
crates/libgraphql-core-v1/src/validators/tests/mod.rs	Wires up validator unit tests.
crates/libgraphql-core-v1/src/validators/tests/object_or_interface_type_validator_tests.rs	Adds test coverage for object/interface implementation validation rules.
crates/libgraphql-core-v1/src/validators/tests/union_type_validator_tests.rs	Adds test coverage for union member validation rules.
crates/libgraphql-core-v1/src/validators/tests/input_object_type_validator_tests.rs	Adds test coverage for input object field validation and cycle detection.
crates/libgraphql-core-v1/src/validators/tests/directive_definition_validator_tests.rs	Adds test coverage for directive definition parameter validation.
crates/libgraphql-core-v1/src/schema/type_validation_error.rs	Updates error formatting for circular input field chains.
crates/libgraphql-core-v1/src/schema/tests/type_validation_error_tests.rs	Adjusts tests to match updated error display formatting.

Comments suppressed due to low confidence (1)

crates/libgraphql-core-v1/src/schema/type_validation_error.rs:66

• CircularInputFieldChain Display wraps each path element in backticks, but the validator currently builds circular_field_path elements that already include backticks (e.g. "A" / "A.b"). This will produce double backticks in real error messages (e.g. "A"). Prefer storing raw path segments (no backticks) in circular_field_path and only formatting in Display, or revert this Display change and keep formatting at the source consistently.

    #[error(
        "circular non-nullable input field chain: {}",
        circular_field_path.iter().map(|t| format!("`{t}`")).collect::<Vec<_>>().join(" -> "),
    )]
    CircularInputFieldChain {
        circular_field_path: Vec<String>,
    },

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[jeffmo]

Code review by graphql-rust-reviewer (Opus 1M) — 3 bugs, 4 test gaps, 1 spec gap, 1 nit:

Bugs (must fix):

1. (moderate) input_object_type_validator.rs: Double backtick wrapping — validator wraps path items in backticks, then #[error] wraps again. Produces \`A.b``instead of`A.b``.
2. (moderate) input_object_type_validator.rs:114-155: Path leaking — extend_from_slice pushes 2 items but only 1 pop() at line 155. Stale entries accumulate across field iterations, producing incorrect cycle paths.
3. (moderate) input_object_type_validator.rs:161-173: [A!]! should break circular chains per spec. Current code only breaks on nullable lists. Spec says ANY list type breaks cycles (empty list is always constructible).

Spec gap:
4. (minor) object_or_interface_type_validator.rs: Missing IsValidImplementation step 2.f — deprecated field consistency check. May be intentionally deferred from v0.

Test gaps:
5. (minor) No test for self-referencing input object (A -> A cycle)
6. (minor) No test for three-node circular chain (A -> B -> C -> A)
7. (minor) No test for list-type cycle breaking ([A!]!)
8. (minor) No test with InterfaceType as the validated type (all tests use ObjectType)

Nit:
9. Directive validator reuses InvalidParameterWithOutputOnlyType awkwardly — both field_name and type_name set to directive display name, producing @auth.@auth(param).

[jeffmo]

All 9 items from the review addressed:

1. Double backtick (bug) — removed backtick wrapping from validator; thiserror handles it
2. Path leaking (bug) — added second pop() for the double extend_from_slice push
3. List type cycle-breaking (spec) — renamed to annot_breaks_circular_chain, List arm unconditionally returns true per spec rule 3
4. Deprecated field consistency (spec gap) — added TODO comment in validator + validation checklist item in plan
5. Self-ref test — added circular_self_reference_detected
6. Three-node test — added circular_three_node_chain_detected
7. List-break test — added list_type_breaks_circular_chain
8. InterfaceType test — added interface_implementing_interface_validates
9. Directive param error — type_name set to empty string for cleaner message

Also fixed: all multi-line spec URLs consolidated to single lines, recursive child validator uses correct interface set.

174 tests pass.

[jeffmo]

Code review of Task 15: Validators.

Overall this is a solid implementation. The validators cover the key spec rules correctly, tests are well-structured with appropriate spec references, and the code is clean. I found 5 findings -- 1 bug, 2 test quality issues, and 2 style nits.

All tests pass, clippy is clean (with --tests), and spec references use the current September 2025 edition.

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 4 comments.

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Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 2 comments.

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[jeffmo]

Round 6 code review -- final sanity pass. All tests pass, clippy is clean, imports are sorted, enum variants are alphabetically ordered, spec URLs are September 2025. Reviewed all 22 changed .rs files. Two low-severity observations below; no bugs or spec compliance gaps found.

[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated 2 comments.

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Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 25 out of 25 changed files in this pull request and generated 3 comments.

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