feat: add @x-<keyword> directive for vendor schema extensions

[Andrei Kvapil (kvaps)]

What

Adds a vendor-neutral @x-<keyword> directive to the JSDoc-like annotation grammar parsed from Helm values.yaml comments. It lets a chart author attach any OpenAPI/JSON-Schema vendor extension keyword (any key starting with x-) to a @param or @field. The directive name carries the keyword, and the value is parsed as YAML flow:

## @param {string} instanceType - Virtual Machine instance type.
## @x-cozystack-options {source: instancetype}
instanceType: "u1.medium"

emits into the generated JSON schema:

"instanceType": { "type": "string", "description": "...", "x-cozystack-options": { "source": "instancetype" } }

Declared on a typedef field, the extension propagates everywhere the type is used — including []Type (items.properties) and map[string]Type (additionalProperties.properties).

Why

This is a generic x-* passthrough mechanism: any x-foo-bar key works and nothing is interpreted or hardcoded. The motivating consumer is cozystack's dynamic-dropdown UI, which reads x-cozystack-options.source from the schema to populate selectable values — but the directive is useful for any tool that consumes vendor extensions.

Behavior

• Multiple @x-* lines are allowed on one field (distinct keys).
• Values may be objects, arrays or scalars.
• Extensions are emitted into values.schema.json only; they never leak into the generated Go types (-g), which remain pure data shapes. README generation is unaffected.

Tests

Covers top-level @param extensions, typedef @field propagation through direct/array/map usage, object/array/scalar value types, multiple extensions per field, non-collision with built-in directives, and an assertion that no x- key appears in generated Go types. go build, go test, and gofmt are clean.

[coderabbitai]

Warning

Review limit reached

@kvaps, we couldn't start this review because you've reached your PR review rate limit.

More reviews will be available in 51 minutes and 52 seconds. Learn how PR review limits work.

Your organization has run out of usage credits. Purchase more in the billing tab.

⌛ How to resolve this issue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

We recommend that you space out your commits to avoid hitting the rate limit.

🚦 How do rate limits work?

CodeRabbit enforces hourly rate limits for each developer per organization.

Our paid plans include higher PR review limits than trial, open-source, and free plans. In all cases, reviews become available again over time. During sustained high-volume PR review activity, CodeRabbit may temporarily slow when the next review becomes available.

Please see our Fair Usage Limits Policy for further information.

ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: 2a83adc3-a7e9-4aa3-95b9-7190d8c55de4

📥 Commits

Reviewing files that changed from the base of the PR and between 56fefc1 and 1aad9ba.

📒 Files selected for processing (4)

• README.md
• internal/openapi/extensions_test.go
• internal/openapi/openapi.go
• internal/patterns/patterns.go

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/vendor-extension-directive

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

[gemini-code-assist]

Code Review

This pull request introduces support for OpenAPI/JSON-Schema vendor extensions (keys starting with x-) via @x-<keyword> directives, which are emitted into the generated JSON schema but excluded from Go types. The feedback highlights a limitation in the current implementation of injectExtensions, which only supports one level of array or map nesting. It is recommended to introduce a recursive unwrapSchema helper to handle arbitrary nesting levels and to expand the test suite to cover these nested structures.

Important

The consumer version of Gemini Code Assist on GitHub is being sunset. Starting June 18, 2026, new organization installations will be blocked, and all code review activity will officially cease on July 17, 2026.
For more details on the timeline and next steps, please review the Help Documentation.

[gemini-code-assist]

The current implementation of injectExtensions and injectExtensionsForElement only supports one level of array or map nesting (e.g., []Type or map[string]Type). If a type is nested deeper (e.g., [][]Type or map[string][]Type), the properties of the underlying struct will not have their extensions injected because injectExtensionsForElement expects the direct element schema to contain properties.

We can simplify the implementation and support arbitrary nesting levels of arrays and maps by introducing a helper function unwrapSchema that recursively traverses down items and additionalProperties until it finds the underlying object schema, and then applying the extensions to its properties. This also eliminates the duplicated property-traversal logic in injectExtensionsForElement.

// unwrapSchema traverses down array items and map additionalProperties to find the underlying object schema.
func unwrapSchema(schema map[string]interface{}) map[string]interface{} {
	if items, ok := schema["items"].(map[string]interface{}); ok {
		return unwrapSchema(items)
	}
	if ap, ok := schema["additionalProperties"].(map[string]interface{}); ok {
		return unwrapSchema(ap)
	}
	return schema
}

// injectExtensions walks a marshaled JSON schema node alongside its
// corresponding Node, writing any vendor extensions (x-* keys) declared on
// the node and recursively descending into nested object properties, array
// items and map values. Extensions are emitted into the JSON schema only.
func injectExtensions(schema map[string]interface{}, n *Node, aliases map[string]*Node) {
	if schema == nil || n == nil {
		return
	}

	for k, v := range n.Extensions {
		schema[k] = v
	}

	children := structuralChildren(n, aliases)
	if children == nil {
		return
	}

	target := unwrapSchema(schema)
	if props, ok := target["properties"].(map[string]interface{}); ok {
		for name, child := range children {
			if sub, ok := props[name].(map[string]interface{}); ok {
				injectExtensions(sub, child, aliases)
			}
		}
	}
}

[gemini-code-assist]

To ensure that vendor extensions propagate correctly through arbitrarily nested arrays and maps (e.g., [][]GPU), we should expand the test suite to cover nested structures. This will prevent future regressions.

func TestVendorExtensionOnTypedefFieldPropagates(t *testing.T) {
	const yaml = `
## @typedef {struct} GPU - GPU device configuration.
## @field {string} name - The name of the GPU resource to attach.
## @x-cozystack-options {source: gpu}

## @param {GPU} gpu - Single GPU.
gpu: {}

## @param {[]GPU} gpus - GPU list.
gpus: []

## @param {map[string]GPU} gpuMap - GPU map.
gpuMap: {}

## @param {[][]GPU} nestedGpus - Nested GPU list.
nestedGpus: []
`
	props := schemaProps(t, yaml)

	want := map[string]any{"source": "gpu"}

	// Direct use: gpu.properties.name
	gpu := props["gpu"].(map[string]any)
	gpuName := gpu["properties"].(map[string]any)["name"].(map[string]any)
	require.Equal(t, want, gpuName["x-cozystack-options"])

	// Array use: gpus.items.properties.name
	gpus := props["gpus"].(map[string]any)
	items := gpus["items"].(map[string]any)
	itemName := items["properties"].(map[string]any)["name"].(map[string]any)
	require.Equal(t, want, itemName["x-cozystack-options"])

	// Map use: gpuMap.additionalProperties.properties.name
	gpuMap := props["gpuMap"].(map[string]any)
	ap := gpuMap["additionalProperties"].(map[string]any)
	apName := ap["properties"].(map[string]any)["name"].(map[string]any)
	require.Equal(t, want, apName["x-cozystack-options"])

	// Nested array use: nestedGpus.items.items.properties.name
	nestedGpus := props["nestedGpus"].(map[string]any)
	innerItems := nestedGpus["items"].(map[string]any)["items"].(map[string]any)
	nestedName := innerItems["properties"].(map[string]any)["name"].(map[string]any)
	require.Equal(t, want, nestedName["x-cozystack-options"])
}

[Aleksei Sviridkin (lexfrei)]

LGTM — correct, well-tested, and byte-compatible with the existing generator for its documented scope. The two findings below are non-blocking and tracked as follow-up issues.

Business context: adds a vendor-neutral @x-<keyword> directive so a chart author can attach arbitrary OpenAPI/JSON-Schema x-* vendor extensions to a @param/@field, emitted into values.schema.json only.

The design is sound. The hard part — injecting non-struct x-* keys without disturbing the struct-field key order that JSONSchemaProps marshaling produces — is handled by a fast-path / injection-path split plus an order-preserving orderedMap, and the byte-identity guarantee is locked down by golden tests (TestSchemaKeyOrderPreservedWithoutExtensions, TestSchemaKeyOrderWithExtensionInsertedAtEnd). The directive cannot collide with built-ins (none start with x-), invalid YAML values fail loudly, and an @x-* line before any @param is safely ignored.

Non-blocking follow-ups

1. Vendor extensions are silently dropped when a typedef type is referenced through more than one container layer ([][]Type, map[string][]Type) — injectExtensionsForElement descends only one level. Single-level cases ([]Type, map[string]Type) work and are tested. Cheap to fix and it simplifies the walker, so worth doing before merge. Tracked in #28.
2. The exported WriteValuesSchema helper (nil root) routes to the fallback branch, which neither preserves key order nor injects extensions. Not a regression and the CLI path is unaffected; worth a doc comment. Tracked in #29.

[Aleksei Sviridkin (lexfrei)]

Only elem["properties"] is inspected here, so a type referenced through more than one container layer ([][]Type, map[string][]Type) never gets its extension injected — the walker stops at the first items/additionalProperties. See #28.