aws / aws/jsii-compiler

Disallow argument mismatch between interface and implementation

Open
#1,320 1 comment 0 reactions 0 assignees View on GitHub
enhancement p1
Dominant language
TypeScript
Stars
50
Forks
26
Avg merge
7h 10m
Merged PRs (30d)
37

Description

Currently, the compiler will allow the following program:

```typescript
export interface IAdder {
add(a: number, b: number): number;
}

export class Adder implements IAdder {
public add(a1: number, b1: number): number {
return a1 + b1;
}
}
```

Notice the argument names in `Adder.add` are different from `IAdder.add`.

This results in an incompatibility between the `IAdder` interface and the `Adder` class in python. See:

- https://github.com/aws/aws-cdk/issues/27852
- https://github.com/aws/jsii/issues/4541
- https://github.com/aws/aws-cdk/issues/21099
- https://github.com/aws/aws-cdk/issues/20125

We should have the compiler enforce that functions in implementations (or subclasses) use the same argument names as the parent.

### Notes

- Unless we roll out a new major version, we cannot start enforcing this on existing projects because the fix would have to be argument renaming, and this [would be a breaking change](https://github.com/aws/jsii/pull/2937). In order to maintain backwards compatibility and stop the proliferation of this mistake, we need to provide an allow list mechanism to ignore existing violations, as well as a feature toggle to activate this validation. In the next major version of the compiler, we can remove these provisions and start enforcing it.
- It would be nice to resurrect and merge https://github.com/aws/jsii/pull/2937 as well, as this would protect us against accidental renaming, either in an attempt to fix the inconsistency, or just an ad-hoc decision to rename some arguments.

Contributor guide

Open the contributing guide

Research direction

No source files or tests are named. Start by tracing the compiler's validation of interface implementations and subclasses, then review the compatibility requirements in the issue and the historical jsii PR #2937. Done means argument-name mismatches are validated with an allow list and feature toggle, while existing projects remain supported.

Written by the indexing model from the issue text.

Assessment

Tech stack
typescript
Domain
compilers
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.