[alexzautke]

Description

ResourceSchema.GetMetaProfileSchemas built a Canonical from every meta.profile value with (string)pn.GetValue()!. This method runs for every resource, so validation threw instead of returning an outcome when:

• an entry has no value. This is valid FHIR when the entry only carries an extension, e.g. "_profile": [{"extension": [...]}]. It threw ArgumentNullException in every parse mode, including Strict.
• a lenient parse (SyntaxOnly, Recoverable) kept a non-string JSON value, e.g. "profile": [5]. It threw InvalidCastException.

Neither case names a profile, so only string values are taken now (.OfType<string>()). Nothing changes for valid profile URLs.

Not covered here:

• With this fix, "profile": [5] still throws, but later, in CanonicalValidator. Its Canonical.Value getter throws on a non-string raw value. That is the wrong-typed-value problem from Investigate and fix our fatal errors. #559/Investigate and fix errors in the model that lead to fatals on the validator #561, which also makes the primitive-bad test case expect a -1 crash.
• Found while testing: on STU3, ExtensionContextValidator accepts a DATATYPE context only when it is "Any" (ExtensionContextValidator.cs:107), not "*". So STU3 extensions with context datatype *, such as data-absent-reason, are reported as "used outside of appropriate contexts" wherever they appear. The new shared test uses iso21090-nullFlavor on STU3 to work around this.

Related issues

Closes #710

Testing

• New ResourceSchemaTests.MetaProfileWithoutStringValueIsSkipped: an entry with only an extension, and a number value, parsed in SyntaxOnly mode. Only the string profile is returned.
• New ResourceSchemaValidationTests.ValidatesMetaProfileWithoutValue (shared, so it runs on STU3/R4/R4B/R5): a Patient whose only meta.profile entry carries an extension validates without issues.
• Both fail without the fix (with ArgumentNullException / InvalidCastException) and pass with it.
• dotnet build Firely.Validator.API.slnx -c Release and all test projects pass: Firely.Fhir.Validation.Tests 335, Compilation R4 505, R4B 136, R5 331, STU3 177 (3 skipped per Compilation project, as on develop). No schema snapshot changes.
• A separate review pass on the diff found nothing blocking. Its one nit, a comment that overstated what the element validators report, is applied.

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Generated by Claude Code

[Copilot]

🟢 Approval recommended

The narrow filtering change preserves valid profile behavior and has targeted regression coverage, with no unresolved findings.

No open issues 🎉

What changed in this PR

Fixes profile selection to ignore meta.profile entries without string values while preserving valid profile URLs.

Changes:

• Filters out null and non-string values before constructing canonicals.
• Adds regression tests for profile selection and extension-only entries across FHIR versions.

File	Description
test/​Firely.Fhir.Validation.Tests/​Impl/​ResourceSchemaTests.cs	Tests skipping null and numeric profile values.
test/​Firely.Fhir.Validation.Compilation.Tests.Shared/​ResourceSchemaValidationTests.cs	Tests validation of extension-only profile entries.
src/​Firely.Fhir.Validation/​Impl/​ResourceSchema.cs	Limits profile selection to string values.

_{Review effort: Balanced}