Schema validation ensuring data schema path matches what is set for the data ref

Author: RossBugginsNHS

scripts/config/vale/styles/config/vocabularies/words/accept.txt

@@ -72,6 +72,7 @@ Python
 quotingType
 rawContent
 repo
+Rollout
 rootDir
 sample_event_markdown
 sample_service_markdown

scripts/config/vale/vale.ini

@@ -6,3 +6,6 @@ Vocab = words
 
 [*.md]
 BasedOnStyles = Vale
+
+[src/changelog/agents.md]
+BasedOnStyles =

scripts/githooks/check-todos.sh

@@ -41,6 +41,7 @@ EXCLUDED_DIRS=(
   "docs/"
   "node_modules/"
   ".devcontainer/"
+  "src/changelog"
 )
 
 

src/changelog/2025-11-13/001-00-readme-schema-dataschema-ref-consistency.md

@@ -0,0 +1,225 @@
+# Schema Dataschema Consistency Validation
+
+**Status**: 🚧 In Development
+**Last Updated**: 2025-11-13 15:20 GMT
+
+## What It Does
+
+This validation tool ensures consistency in CloudEvents event schemas by checking that the `dataschema` const value matches the `data` $ref value.
+
+In CloudEvents schemas, these two properties should always reference the same schema file:
+
+```yaml
+dataschema:
+  type: string
+  const: ../data/digital-letter-base-data.schema.yaml  # Must match
+data:
+  $ref: ../data/digital-letter-base-data.schema.yaml   # Must match
+```
+
+The validator automatically detects mismatches and reports them clearly.
+
+## Why It Matters
+
+Mismatched `dataschema` and `data` references can cause:
+
+- Runtime validation failures
+- Confusing error messages
+- Incorrect schema documentation
+- Integration issues with event consumers
+
+This validation catches these issues early in development.
+
+## Quick Start
+
+### Validate Your Schemas
+
+```bash
+# Validate all event schemas in current directory
+npm run validate:dataschema-consistency
+
+# Or use make
+make validate-dataschema-consistency
+
+# Validate specific directory
+npm run validate:dataschema-consistency -- /path/to/schemas
+```
+
+### Expected Output
+
+**When all schemas are valid**:
+
+```plaintext
+✓ Validating event schemas...
+✓ Found 22 schema files
+✓ All schemas valid - no mismatches detected
+```
+
+**When mismatches are found**:
+
+```plaintext
+✗ Validation failed for 2 schemas:
+
+  File: uk.nhs.notify.digital.letters.event.v1.schema.yaml
+  Error: dataschema const does not match data $ref
+    Expected: ../data/schema-a.yaml
+    Actual:   ../data/schema-b.yaml
+
+  File: another-event.v1.schema.yaml
+  Error: dataschema const does not match data $ref
+    Expected: ../data/correct-schema.yaml
+    Actual:   ../data/wrong-schema.yaml
+
+✗ 2 validation errors found
+```
+
+## Usage
+
+### In Development
+
+Run validation before committing schema changes:
+
+```bash
+# Add to your workflow
+git add src/cloudevents/domains/*/events/*.yaml
+make validate-dataschema-consistency
+git commit -m "feat: add new event schema"
+```
+
+### In CI/CD
+
+The validation runs automatically in the CI/CD pipeline:
+
+- **Pull Requests**: Validates all schema files
+- **Main Branch**: Runs on every commit
+- **Failure**: Pipeline fails if mismatches detected
+
+### Programmatic Use
+
+Use the validation function directly in your code:
+
+```typescript
+import { validateDataschemaConsistency } from './validator-lib';
+
+const schema = {
+  properties: {
+    dataschema: {
+      const: '../data/schema.yaml'
+    },
+    data: {
+      $ref: '../data/schema.yaml'
+    }
+  }
+};
+
+const result = validateDataschemaConsistency(schema);
+
+if (!result.valid) {
+  console.error(result.errorMessage);
+  console.log(`Expected: ${result.dataschemaValue}`);
+  console.log(`Actual: ${result.dataRefValue}`);
+}
+```
+
+## What Gets Validated
+
+### Validated Schemas
+
+The tool checks schemas that have BOTH:
+
+- A `properties.dataschema.const` value
+- A `properties.data.$ref` value
+
+### Skipped Schemas
+
+Schemas are automatically skipped (no error) if they:
+
+- Don't have a `dataschema` property
+- Don't have a `data` property
+- Are not CloudEvents event schemas
+
+### Validation Rules
+
+1. **Exact Match**: Values must match exactly (case-sensitive)
+2. **No Whitespace**: Trailing/leading spaces cause validation failure
+3. **String Only**: Both values must be strings
+4. **Not Null**: Null or undefined values fail validation
+
+## Common Issues
+
+### Mismatch Detected
+
+**Problem**: Validator reports mismatch
+
+**Solution**: Update schema to use consistent reference:
+
+```yaml
+# Before (incorrect)
+dataschema:
+  const: ../data/old-schema.yaml
+data:
+  $ref: ../data/new-schema.yaml
+
+# After (correct)
+dataschema:
+  const: ../data/new-schema.yaml
+data:
+  $ref: ../data/new-schema.yaml
+```
+
+### Case Sensitivity
+
+**Problem**: `Schema.yaml` vs `schema.yaml`
+
+**Solution**: Ensure exact case match:
+
+```yaml
+# Both must use same case
+dataschema:
+  const: ../data/Schema.yaml  # Capital S
+data:
+  $ref: ../data/Schema.yaml   # Capital S
+```
+
+### Whitespace Issues
+
+**Problem**: Hidden spaces cause validation failure
+
+**Solution**: Remove trailing whitespace:
+
+```yaml
+# Before (incorrect - space after .yaml)
+dataschema:
+  const: ../data/schema.yaml
+
+# After (correct)
+dataschema:
+  const: ../data/schema.yaml
+```
+
+## Where to Get Help
+
+- **Documentation**: See `/src/changelog/2025-11-13/001-01-request-*.md` for background
+- **Requirements**: See `/src/changelog/2025-11-13/001-03-requirements-*.md` for detailed specs
+- **Issues**: Report problems in GitHub Issues
+- **Questions**: Ask in team channels
+
+## Development Status
+
+### Current Status: 🚧 In Development
+
+- ✅ Validation logic implemented and tested
+- ⏳ CLI script in progress
+- ⏳ CI/CD integration pending
+- ⏳ Documentation being refined
+
+### Upcoming
+
+- Full CI/CD pipeline integration
+- Additional validation rules if needed
+- Performance optimizations
+- Enhanced error messages
+
+---
+
+**Note**: This document will be updated as the feature develops. Check the "Last Updated" timestamp above.

src/changelog/2025-11-13/001-01-request-schema-dataschema-ref-consistency.md

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+# Schema Consistency Validation Enhancement
+
+**Date**: 2025-11-13 14:31 GMT
+**Branch**: rossbugginsnhs/2025-11-13/schema-restrictions
+
+## Objective
+
+Enhance the CloudEvents validator at `src/cloudevents/tools/validator` to enforce consistency between `dataschema` const values and `data` $ref values across all event schemas.
+
+### Current Pattern in Event Schemas
+
+All event schemas follow this pattern:
+
+```yaml
+dataschema:
+  type: string
+  const: ../data/digital-letter-base-data.schema.yaml
+  description: Canonical URI of the example event's data schema.
+data:
+  $ref: ../data/digital-letter-base-data.schema.yaml
+  description: Example payload wrapper containing notify-payload.
+```
+
+### Challenge
+
+- `dataschema.const` is a literal value that validates instance data
+- `data.$ref` is schema metadata that tells validators which schema to use
+- JSON Schema has no built-in way to cross-reference between literal values and schema keywords
+
+### Proposed Solution
+
+Add validation to the existing validator tool at `src/cloudevents/tools/validator` to:
+
+1. Parse event schema files
+2. Extract the `dataschema.const` value
+3. Extract the `data.$ref` value
+4. Fail validation if they don't match
+
+This would be integrated into the existing validation tooling and CI/CD pipeline to ensure consistency across all 22+ event schemas that follow this pattern.
+
+## Next Steps
+
+1. Create a validation function in `validator-lib.ts`
+2. Add a standalone validation script or extend existing validator
+3. Add tests for the new validation
+4. Integrate into CI/CD pipeline

src/changelog/2025-11-13/001-02-plan-schema-dataschema-ref-consistency.md

@@ -0,0 +1,101 @@
+# Implementation Plan: Schema Consistency Validation
+
+**Date**: 2025-11-13 14:38 GMT
+**Branch**: rossbugginsnhs/2025-11-13/schema-restrictions
+**Related Request**: [001-01-request-schema-dataschema-ref-consistency.md](./001-01-request-schema-dataschema-ref-consistency.md)## Overview
+
+Add validation to ensure that in CloudEvents event schemas, the `dataschema` const value matches the `data` $ref value.
+
+## Implementation Steps
+
+### 1. Create New Validation Library
+
+Create a new library file `dataschema-consistency-lib.ts` with validation function:
+
+- Export `validateDataschemaConsistency(schemaObject)` function
+- Export `DataschemaConsistencyResult` interface type
+- Checks if the schema has both `properties.dataschema.const` and `properties.data.$ref`
+- Returns validation result with details if they don't match
+- Returns success if they match or if the pattern doesn't apply
+
+**Location**: `src/cloudevents/tools/validator/dataschema-consistency-lib.ts`
+
+**Rationale**: Create new file instead of modifying existing validator-lib.ts to keep changes isolated and avoid impacting existing validation functionality.
+
+### 2. Create Standalone Validation Script
+
+Create a script that:
+
+- Scans all event schema files in specified directories
+- Validates each schema for dataschema/data consistency
+- Reports all inconsistencies
+- Exits with error code if any inconsistencies found
+- Imports from the new dataschema-consistency-lib.ts
+
+**Location**: `src/cloudevents/tools/validator/validate-dataschema-consistency.ts`
+
+### 3. Add Unit Tests
+
+Create comprehensive tests for:
+
+- Matching dataschema and data values (should pass)
+- Mismatched values (should fail with clear message)
+- Schemas without dataschema property (should skip)
+- Schemas without data property (should skip)
+- Edge cases (null, undefined, different path formats)
+
+**Location**: `src/cloudevents/tools/validator/__tests__/validate-dataschema-consistency.test.ts`
+
+**Note**: Tests will import from `dataschema-consistency-lib` (new file), not from existing validator-lib.
+
+### 4. Update Makefile
+
+Add a new make target to run the consistency validation:
+
+```makefile
+validate-dataschema-consistency:
+    npm run validate:dataschema-consistency
+```
+
+**Location**: `src/cloudevents/Makefile`
+
+### 5. Update package.json
+
+Add script to run the consistency validator:
+
+```json
+"validate:dataschema-consistency": "tsx tools/validator/validate-dataschema-consistency.ts"
+```
+
+**Location**: `src/cloudevents/package.json`
+
+### 6. Integrate into CI/CD Pipeline
+
+Add validation step to the existing validation workflow or create new step.
+
+**Location**: `.github/workflows/` or relevant CI/CD configuration
+
+## Success Criteria
+
+- [ ] Validation function correctly identifies matching dataschema/data pairs
+- [ ] Validation function correctly identifies mismatches with helpful error messages
+- [ ] All 22+ existing event schemas pass validation
+- [ ] Unit tests achieve 100% code coverage for new functions
+- [ ] Script can be run standalone via `make` or `npm run`
+- [ ] Integration into CI/CD prevents merging schemas with inconsistencies
+- [ ] Documentation updated if needed
+
+## Testing Strategy
+
+1. Run against all existing event schemas to ensure they currently pass
+2. Create test schemas with intentional mismatches to verify detection
+3. Test edge cases (missing properties, null values, etc.)
+4. Verify error messages are clear and actionable
+
+## Rollout Plan
+
+1. Implement and test locally
+2. Run against all existing schemas to verify current state
+3. Add to CI/CD pipeline as warning initially
+4. Monitor for false positives
+5. Convert to blocking validation once confident