`fk_related_tables` not working correctly with two foreign keys to same table

[Nutomic]

Rust Version

1.89

Diesel Version

latest master (d02221c)

Diesel Features

postgres

Database Version

17.5

Operating System Version

Manjaro Linux

What happened?

We have a database table with two foreign keys that both reference the same table. After upgrading to diesel-cli 2.3.2 and enabling the new feature allow_tables_to_appear_in_same_query_config = "fk_related_tables" this table is missing from allow_tables_to_appear_in_same_query in the generated schema. If allow_tables_to_appear_in_same_query_config is not specified, diesel::allow_tables_to_appear_in_same_query is correct. diesel::joinable! is also missing for this relation, but this probably makes sense as diesel cant join the tables automatically.

What did you expect to happen?

diesel::allow_tables_to_appear_in_same_query should include tables with multiple foreign keys to the same table.

Additional details

No response

Steps to reproduce

I wrote a test case on this branch, you can run it by cloning and then running cargo t --no-default-features --features postgres print_schema_fk_related_tables.

Here is the output:

Snapshot file: diesel_cli/tests/print_schema/print_schema_fk_related_tables/postgres/expected.snap
Snapshot: expected
Source: diesel_cli/tests/print_schema.rs:534
────────────────────────────
Test: print_schema_fk_related_tables
─────────────────────────────
-old snapshot
+new results
────────────┬───────────────
45    45 │         id -> Int4,
46    46 │     }
47    47 │ }
48    48 │
49       │-diesel::joinable!(comments -> posts (post_id));
50    49 │ diesel::joinable!(posts -> users (user_id));
51    50 │ diesel::joinable!(transactions -> sessions (session_id));
52    51 │
53       │-diesel::allow_tables_to_appear_in_same_query!(comments, posts, users,);
52 │+diesel::allow_tables_to_appear_in_same_query!(posts, users,);
54    53 │ diesel::allow_tables_to_appear_in_same_query!(sessions, transactions,);
────────────┴──────────────────

Compile time error

No response

Checklist

• I have already looked over the issue tracker and the discussion forum for similar possible closed issues.

• This issue can be reproduced on Rust's stable channel. (Please submit the issue in the Rust issue tracker instead if that's not the case)

• This issue can be reproduced without requiring a third party crate

[weiznich]

Thanks for reporting.

I think the issue here is that we filter out such duplicated foreign key constraints before generating the schema as they are not unambiguous. Before we used these data only to generate joinable! calls, so that was not a problem.

The filtering happens here: https://github.com/diesel-rs/diesel/blob/master/diesel_cli/src/print_schema.rs#L172-L173

What we need to do to fix this is to move the filtering to happen rather directly before generating the joinable! calls so that this doesn't affect the allow_tables_to_appear_in_same_query! generation. That should happen somewhere here. We also want to include the test case provided by @Nutomic.

A PR fixing that would be very welcome

[CreditWorthy]

I can try and get an pr in for this by the end of the week or sooner :)

[Muktarsadiq]

Is This still available ?

[weiznich]

@CreditWorthy Do you still work on this or would you like to have help from @Muktarsadiq ?

[sim-hash]

@weiznich I hope it’s okay to reach out like this. I’d like to pick this one up if @CreditWorthy is finished with it. If not, feel free to assign me anything else that could use some help.