ADR: Custom Exceptions Patterns #186
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jwm4
approved these changes
Jan 29, 2025
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| The historically pervasive pattern for exception handling during application runtime is to catch internally raised exceptions in the CLI layer and use `click.secho` followed by `click.exceptions.Exit` to display a useful error message to the user before exiting the application. This leaves a risk of intermediate calls between the site of the exception and the user-facing layer changing, leading to missed new exceptions and outdated caught exceptions. A second issue is that of discoverability and verification: given a `click.exceptions.Exit` exception handling, it is not clear from the code where the caught exception originates from in the call stack, and, similarly, given a piece of code that can raise an exception, it is not clear from the local code whether that exception is properly handled in the CLI layer without investigation. | ||
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| These issues will compound whenever REST APIs begin development. |
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and/or whenever the SDK APIs begin development.
nathan-weinberg
approved these changes
Jan 29, 2025
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Generally I agree with this, worth calling out that some of this work is ongoing in the Core repo as part of instructlab/instructlab#2325
Signed-off-by: Anastas Stoyanovsky <astoyano@redhat.com>
This was referenced Jan 30, 2025
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booxter
reviewed
Jan 30, 2025
| * CLI layer error handling will be easy to understand and trace. | ||
| * Whenever REST APIs are developed, HTTP error codes should be easier to be associated with specific exceptions. | ||
| * It should be easier to compose useful error messages for the user. | ||
| * It should be easier to correctly scope exception handling (consider a `URLError` raised about SSL verification, for example, versus a custom `SSlVerificationException`). |
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I'm with you in general but not for this specific example (as I expressed in the patch), for the reason that we cannot and should not enumerate all the possible ways a request may fail, so letting URLError bubble up is fine here. (Caught further up the call stack and transformed into ilab specific exception as needed.)
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