[hanneshayashi]

Closes #14

Problem

OpenAPI 3.0 only accepts null for a nullable: true enum if null is listed in the enum, so specs (and vacuum's nullable-enum-contains-null rule) list it:

public:
  type: string
  nullable: true
  enum: [editor, viewer, null]

GetStringValidators, GetIntegerValidators and GetFloatValidators decode each enum node into a Go value and only skip it when Decode returns an error. Decoding a YAML null returns no error and leaves the zero value, so the generated validator was stringvalidator.OneOf("editor", "viewer", "") (or 0 for integer/number enums). The downstream framework generator also appends the values to the description, which produced Possible values: `editor`, `viewer`, ``.

Solution

• Skip enum nodes whose ShortTag() is !!null before decoding, in the string, int64 and float64 paths. A quoted "null" or "" is still a string and stays an allowed value.
• An enum that only lists null now produces no validator, since the *ValidatorOneOf helpers already return nil for an empty slice.
• Document the behavior in DESIGN.md.

Tests

• TestGetStringValidators, TestGetIntegerValidators, TestGetFloatValidators: enum-with-null and enum-only-null cases. The string test also has enum-with-quoted-null-string. All of these fail without the fix.
• Edgecase golden spec: new nullable_enum resource (OAS 3.1 type: [<t>, "null"]) with string, integer, double and null-only enums. It covers the real libopenapi parse path. Without the fix, TestGenerate_WithConfig/EdgeCase_API fails with ""/0 in all four validators. No other golden file changes.
• Verified make generate in terraform-provider-doit with the spec from doiteng/omni#69368 (via a local replace). doit_sharing.public is back to OneOf("editor", "viewer") in the IR, sharing_resource_gen.go and docs/resources/sharing.md, and the rest of the generated output is unchanged. Provider make test and make lint pass.

[Copilot]

🟢 Approval recommended

The focused fix consistently handles all three validator paths, includes unit and integration regression coverage, and has no identified blocking issues.

No open issues 🎉

What changed in this PR

Fixes #14 by preventing null enum entries from becoming unintended empty-string or zero values in generated Terraform OneOf validators.

Changes:

• Filters null nodes before decoding string, integer, and float enums.
• Adds unit and golden regression coverage for mixed and null-only enums, plus quoted "null" strings.
• Documents that null-only enums produce no validator.

File	Description
internal/​mapper/​oas/​string.go	Skips null entries in string enums.
internal/​mapper/​oas/​string_test.go	Covers mixed, null-only, and quoted-null string enums.
internal/​mapper/​oas/​number.go	Skips null entries in float enums.
internal/​mapper/​oas/​number_test.go	Covers mixed and null-only float enums.
internal/​mapper/​oas/​integer.go	Skips null entries in integer enums.
internal/​mapper/​oas/​integer_test.go	Covers mixed and null-only integer enums.
internal/​cmd/​testdata/​edgecase/​provider_code_spec.json	Records expected validators without null-derived values.
internal/​cmd/​testdata/​edgecase/​openapi_spec.yml	Adds nullable enum integration fixtures.
internal/​cmd/​testdata/​edgecase/​generator_config.yml	Enables generation for the nullable enum fixture.
DESIGN.md	Documents null enum mapping behavior.

_{Review effort: Balanced}