Only report a subset of the actual and expected for toMatchObject

[geersch]

Clear and concise description of the problem

If you run this test.

describe('diff test', () => {
  it('should compare 2 objects', () => {
    const a = { a: 1, b: 2, c: { d: 4 } };
    const b = { b: 3 };

    expect(a).toMatchObject(b);
  });
});

You get the following output.

It would be clearer if it would strip properties that are not relevant. For example, see getObjectSubset in @jest/expect-utils.

getObjectSubset

After patching the processError function (@vitest/utils) locally.

export function processError(err: any, diffOptions?: DiffOptions) {
...
  if (err.showDiff || (err.showDiff === undefined && err.expected !== undefined && err.actual !== undefined)) {
    ...
    const actualSubset = getObjectSubset(replacedActual, replacedExpected);
    err.actual = actualSubset;
    err.diff = diff(replacedExpected, actualSubset, { ...diffOptions, ...err.diffOptions });
    ...
  }
...
}

I get this output instead.

Which makes it a lot easier to spot the difference.

The output with the VSCode plugin looks like this now.

Perhaps it would be useful to also add this into Vitest?

Suggested solution

Extract a subset of properties from the actual and report that as output.

Alternative

No response

Additional context

No response

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