Validate property values on export to prevent writing invalid files

[ehennestad]

⚠️ Depends on — merge these first:

• fix: export scalar datetime as a scalar dataset #835
• Add context-aware schema violation reporting #836

Motivation

Background

MatNWB v2.9.0 fixed some validation bugs rendering existing NWB files unreadable because of strict validation on read. In issue #776, the consensus is to relax validation on read, showing warnings instead of errors if validation fails.

PR #836 (merged) and PR #830 is ongoing work to support that.

Problem

However, relaxing validation on read creates a new problem. MatNWB currently validates property values only on construction and modification, not on export. If users are allowed to read an NWB file with invalid values, they are also free to re-export those invalid values to new NWB files.

Solution

This PR adds an export-time guard, ensuring that all properties are re-validated on file export.

Changes

• Add types.untyped.MetaClass/validateProperties, invoked in export alongside the existing required-property and custom-constraint checks. For each set property that has a generated validate_<prop> method, it re-runs the validator and discards the result, so there are no setter side effects such as type coercion or column-name syncing. If the value is invalid it raises NWB:Export:InvalidPropertyValue, including the property name and file location, and preserves the original validator error as a cause.
• Empty/unset optional properties are skipped, matching what export writes.
• Validators run in the default (strict) context here, so a schema violation is an error on export even when the same check is lenient during a read.

Relationship to other work

This is the write-side counterpart to the read-side permissiveness in #776 — read lenient (warn, keep value), write strict (error). It generalizes the pattern already used for DynamicTable (checkConfig via the custom-constraint path) to all property validators. Its user-visible effect lands together with #776, so this is best reviewed and merged alongside that work.

How to test

tests.unit.types.MetaClassValidatePropertiesTest exercises the guard with a small MetaClass test double: an invalid property value raises NWB:Export:InvalidPropertyValue with the property name, location, and original cause; an unset (empty) property is skipped; a valid value passes.

Checklist

• Have you ensured the PR description clearly describes the problem and solutions?
• Have you checked to ensure that there aren't other open or previously closed Pull Requests for the same change?
• If this PR fixes an issue, is the first line of the PR description fix #XX where XX is the issue number?

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 97.14286% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 95.29%. Comparing base (d8f55c8) to head (900f47d).

Files with missing lines	Patch %	Lines
+types/+untyped/MetaClass.m	97.14%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #832   +/-   ##
=======================================
  Coverage   95.28%   95.29%           
=======================================
  Files         219      219           
  Lines        7702     7737   +35     
=======================================
+ Hits         7339     7373   +34     
- Misses        363      364    +1     

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[bendichter]

I don't understand the type of invalid workflow you are trying to prevent