Issues with the "Override Source Has Override" specification

[glen-84]

While from is not null

(1) When would from be null?

from must not be in visited.

(2) If it is, should you log the error and break?

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(3) I can't get the 3rd counter-example test case to pass with the current algorithm, unless I move the "from must not be in visited" and "Add from to visited" below "If sourceField is not annotated with @override". If C is added to visited (along with A), then "The size of visited must be equal to the size of overrides" will be true, when false is expected.

I can share code if it helps.

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(4) We may also want to consider splitting this rule for improved error codes and messages, for example:

1. The @override directive on field 'Bill.amount' in schema 'A' contains a circular reference ('A' -> 'B' -> 'A').
2. The field 'Bill.amount' in schema 'C' is overridden in multiple schemas ('A', 'B').

[dariuszkuc]

Per @override definition (Apollo and this spec) from is non-nullable. Guessing validation should ensure that it is non-empty value and points to a known subgraph name.

directive @override(from: String!) on FIELD_DEFINITION

[glen-84]

Per @override definition (Apollo and this spec) from is non-nullable.

The from here refers to a variable, not to the directive attribute. 🙂

Guessing validation should ensure that it is non-empty value and points to a known subgraph name.

I think that would be a separate rule, which I was going to suggest. 👍 Edit: I've opened #114.