feat: incomplete with node on which an error occurred

[WilcoFiers]

Part of #4860

If a check or matches method throws, catch the error and add a node with an error-occurred none check. This way incomplete results are always reported.

This only happens for axe.run / axe.runPartial. rule.runSync() still throws if an occurs in a rule or check.

[WilcoFiers]

Note that I got rid of most of these, and updated how error works:

• error is now serialized so that it can be carried across frame boundaries
• description is clobbered by the reporter. It never even left axe (plus it has a typo)
• message and stack are duplicated on error
• errorNode wasn't getting pulled through nodeSerializer

ErrorNode in particular was a problem. Because it wasn't serialized, it A. doesn't have the frame selector, and B. leaves the _element property on it, which doesn't play well with serialization (axe Extension would completely error out trying to serialize this).

[Copilot]

Pull Request Overview

This PR implements error handling for axe-core checks and rules by catching errors and converting them to incomplete results instead of failing completely. This allows the scanner to report what it could successfully check while noting where errors occurred.

• Introduces a new SupportError class to wrap errors with additional context
• Adds error handling to rule matching and check evaluation phases
• Creates a dedicated "error-occurred" check type for incomplete results

Reviewed Changes

Copilot reviewed 22 out of 23 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
lib/core/utils/support-error.js	New SupportError class for wrapping errors with context
lib/core/utils/serialize-error.js	Utility for serializing errors to JSON
lib/core/base/rule.js	Updated to catch errors and wrap them in SupportError
lib/core/base/audit.js	Added error handling in audit run and after phases
lib/core/utils/merge-results.js	Support for merging error information from frames
lib/checks/shared/error-occurred.json	New check definition for error cases
test/integration/full/error-occurred/*	Integration tests for error handling
test/core/utils/*	Unit tests for new utilities

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[stephenmathieson]

Any reason this is not a class that extends Error? If we're going to rewrite it, we may as well use more modern JS features 🤷‍♂️

[straker]

This is the same as the name so want to just make sure it's different

Suggested change

	const supportError = new SupportError({ error, method: 'test' });
	assert.equal(supportError.method, 'test');
	const supportError = new SupportError({ error, method: '#matches' });
	assert.equal(supportError.method, '#matches');

[straker]

Suggested change

	const supportError = new SupportError({ error, ruleId: 'test' });
	assert.equal(supportError.ruleId, 'test');
	assert.include(supportError.message, 'Skipping test rule.');
	const supportError = new SupportError({ error, ruleId: 'aria' });
	assert.equal(supportError.ruleId, 'aria');
	assert.include(supportError.message, 'Skipping aria rule.');

[straker]

Suggested change

	const supportError = new SupportError({ error, errorNode: 'test' });
	assert.equal(supportError.errorNode, 'test');
	const supportError = new SupportError({ error, errorNode: 'err' });
	assert.equal(supportError.errorNode, 'err');