Dry-run should perform client-side validation to catch failures that actual publish would hit #147

Problem

The current --dry-run implementation only checks whether resources exist in the target APIM instance (GET to determine PUT vs create). It does not validate the merged payload, so dry-run reports success for resources that will fail during actual publish.

Evidence

Comparing tests/test-overrides/extract-dryrun.log (dry-run) vs tests/test-overrides/extract.log (actual publish), dry-run reported all resources as PUT while actual publish hit multiple HTTP 400 validation errors:

Proposed Validations

The dry-run reporter should add client-side validation before reporting PUT. These checks should produce [DRY RUN] WARN lines without blocking the rest of the report. Suggested checks:

1. Named Value display name format

ARM rejects display names with spaces, parentheses, and other special characters. Validate against the pattern: ^[A-Za-z0-9._-]+$.

2. Resource ID format validation

resourceId fields on backends must be valid ARM resource IDs (starting with /subscriptions/). Currently, override values like bare paths pass through unchecked.

3. URL format validation

Backend url fields and API serviceUrl fields should be valid URLs with a scheme (https://, wss://, etc.).

4. Cross-resource reference validation (loggerId)

Diagnostics reference loggers by loggerId. Dry-run should verify the referenced logger exists either in the artifact set or in the target APIM instance. Same applies after override merging — if an override changes loggerId, validate the new value.

5. Circuit breaker rule completeness

ARM requires failureCondition when circuitBreaker.rules is specified. Validate that overrides don't produce partial circuit breaker configs.

6. Key Vault identity pre-check

When a named value references a Key Vault with identityClientId, verify that the identity is present on the target APIM service (the service's managed identities are available via the service resource GET).

7. Logger credential validation

Warn when logger credentials contain placeholder values (e.g., production-instrumentation-key-00000000) that are unlikely to be valid GUIDs or connection strings.

8. Override key validity

Warn when override properties don't match any known field in the resource's ARM schema (typo detection). For example, retryCondition vs the correct failureCondition nesting.

9. Dependency ordering warnings

When a resource depends on another resource that is itself invalid or skipped, warn that downstream resources will likely also fail.

Implementation Notes

• Validations should run after override merging, against the final payload that would be sent to ARM.
• Warnings should not change the exit code — they are advisory. Consider a --strict flag that promotes warnings to errors.
• These are client-side heuristics; ARM will always be the authoritative validator. The goal is to catch the most common mistakes early.

Related Files

• src/services/dry-run-reporter.ts — main dry-run logic
• src/services/override-merger.ts — override merging
• src/lib/config-loader.ts — override loading