index: make Index ancestor methods fallible
#7851
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I think most of the PR description is talking about one of the two commits. Could you move those parts to the commit message of the relevant commit? |
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@martinvonz Just added the additional respective details from the PR description to each of the commit messages. |
yuja
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This is part of a series of changes to make most methods on index traits (i.e. `ChangeIdIndex`, `MutableIndex`, `ReadonlyIndex`, `Index`) fallible. This will enable networked implementations of these traits, which may produce I/O errors during operation. See jj-vcs#7825 for more information. - Introduced a few more instances of the existing anti-pattern, `TODO: indexing error shouldn't be a "BackendError"`. We're tracking this known issue in jj-vcs#7849. - Converted `MutableRepo::merge_view` to return a `RepoLoaderError` instead of a `BackendError`. The only caller, `MutableRepo::merge`, already returns a `RepoLoaderError`. - Added three "`fallible_`" iterator helpers to reduce the amount of noise at `is_ancestor` call sites due to the method now being fallible. Using these helpers seem to produce code that's a little more readable than using `process_results` from itertools. One consideration in this trade-off is that these helpers do not themselves return iterators: if we find that we need more support for fallible combinators mid-"chain" of iterator combinators, we might either want to use `process_results` only in those cases, or switch to use of `process_results` across the board (in lieu of these new helpers).
This is part of a series of changes to make most methods on index traits (i.e. `ChangeIdIndex`, `MutableIndex`, `ReadonlyIndex`, `Index`) fallible. This will enable networked implementations of these traits, which may produce I/O errors during operation. See jj-vcs#7825 for more information. This introduces another instance of the existing anti-pattern, `TODO: indexing error shouldn't be a "BackendError"`. We're tracking this known issue in jj-vcs#7849. Closes jj-vcs#7825.
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This is the last in a series of changes to make most methods on index traits (i.e.
ChangeIdIndex,MutableIndex,ReadonlyIndex,Index) fallible. This will enable networked implementations of these traits, which may produce I/O errors during operation. See #7825 for more information.Previous PRs in this line of work: #7799, #7823, #7830, #7832, #7843.
A few things to note:
TODO: indexing error shouldn't be a "BackendError". Filed issue Task: Improve error handling whereIndexErrors are wrapped inBackendError#7849 to track this.MutableRepo::merge_viewto return aRepoLoaderErrorinstead of aBackendError. The only caller,MutableRepo::merge, already returns aRepoLoaderError.fallible_" iterator helpers to reduce the amount of noise atis_ancestorcall sites due to the method now being fallible. Using these helpers seem to produce code that's a little more readable than usingprocess_resultsfrom itertools. One consideration in this trade-off is that these helpers do not themselves return iterators: if we find that we need more support for fallible combinators mid-"chain" of iterator combinators, we might either want to useprocess_resultsonly in those cases, or switch to use ofprocess_resultsacross the board (in lieu of these new helpers).This closes #7825.
Thanks to Martin, Yuya, and Philip for guidance with these fallibility changes! I appreciate your help.
Checklist
If applicable:
CHANGELOG.mdREADME.md,docs/,demos/)cli/src/config-schema.json)