Fixes issue with multiple nested fragments on interface and union

[letsar]

This PR aims to fix gql-dart/ferry#610.
I don't fully understand the code, so I'm not sure why I needed to use superclassSelections instead of context.hierarchy in inline_fragment_classes.dart, but it seems to work. I've tested it in our codebase and so far I don't see any regression and we can now use the kind of fragments discussed in the issue 🥳 .

[Copilot]

Pull Request Overview

This pull request fixes an issue with nested fragments on interfaces in GraphQL code generation. The fix ensures that nested interface implementations are correctly identified and that specialized type fragments are properly generated from superclass selections rather than the entire hierarchy.

Key changes:

• Added validation to check if nested interface names make sense by verifying containment
• Changed loop iteration from hierarchy keys to superclass selection keys to prevent incorrect fragment generation
• Added comprehensive test coverage for nested fragments on interfaces with new GraphQL schema types (Author, Person, Company, Group, Book, Textbook, ColoringBook)

Reviewed Changes

Copilot reviewed 5 out of 19 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
codegen/gql_code_builder/lib/src/utils/field_utils.dart	Added validation check to ensure nested interface names contain the superName before creating interface implementations
codegen/gql_code_builder/lib/src/inline_fragment_classes.dart	Fixed loop to iterate over superclassSelections.keys instead of context.hierarchy.keys to prevent incorrect fragment generation
codegen/end_to_end_test/test/operation/nested_fragments_on_interface_test.dart	Added comprehensive test coverage for nested fragment deserialization and serialization
codegen/end_to_end_test/lib/graphql/schema.graphql	Extended schema with Author/Book interfaces and their implementations
Multiple generated files	Auto-generated code from the new GraphQL schema and fragments
.gitignore	Added iOS ephemeral directory to gitignore

Files not reviewed (11)

• codegen/end_to_end_test/lib/fragments/generated/hero_with_interface_subtyped_fragments.data.gql.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/hero_with_interface_subtyped_fragments.data.gql.g.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/nested_fragments_on_interface.ast.gql.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/nested_fragments_on_interface.req.gql.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/nested_fragments_on_interface.req.gql.g.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/nested_fragments_on_interface.var.gql.dart: Language not supported
• codegen/end_to_end_test/lib/fragments/generated/nested_fragments_on_interface.var.gql.g.dart: Language not supported
• codegen/end_to_end_test/lib/graphql/generated/schema.ast.gql.dart: Language not supported
• codegen/end_to_end_test/lib/graphql/generated/schema.schema.gql.dart: Language not supported
• codegen/end_to_end_test/lib/graphql/generated/serializers.gql.dart: Language not supported
• codegen/end_to_end_test/lib/graphql/generated/serializers.gql.g.dart: Language not supported

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[knaeckeKami]

Thanks so much for this!

I am currently trying to understand why this would work ;)

Oh...

void addInterface(String name) {
    final parts = name.split("__");           // Split on "__"
    final base = parts[0];                    // e.g., "GHeroData_hero"
    hierarchy.putIfAbsent(base, () => {});    // Create entry for base
    if (parts.length > 1) {                   // If specialized version
      hierarchy[base]!.add(name);             // Add to base's set
    }
  }

I think the culprit is just the naive split on the first __, which breaks down in nested scenarios ...

[letsar]

Hello, I don't have the time right now to explain a little further, but this fix introduced a regression when we use a named Fragment on a specific union type, which select a field which is an interface. I didn't have a simple repro case for now, but I wanted to warn you about this. I didn't look at the addInterface method, but yes maybe, the solution is there after all.

[knaeckeKami]

Thanks! I already stumbled upon this or something similar when trying to write more comprehensive regression tests for this - which is why I did not merge this yet. did not have time to look into it further yet