Add the `jj-core` crate by PhilipMetzger · Pull Request #9766 · jj-vcs/jj

PhilipMetzger · 2026-07-06T16:03:41Z

These are the simple parts of the jj-core extraction, see #6284 (comment) for what this entails.

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If applicable:

I have updated CHANGELOG.md
I have updated the documentation (README.md, docs/, demos/)
I have updated the config schema (cli/src/config-schema.json)
I have added/updated tests to cover my changes
I fully understand the code that I am submitting (what it does,
how it works, how it's organized), including any code drafted by an LLM.
For any prose generated by an LLM, I have proof-read and copy-edited with
an eye towards deleting anything that is irrelevant, clarifying anything
that is confusing, and adding details that are relevant. This includes,
for example, commit descriptions, PR descriptions, and code comments.

yuja · 2026-07-07T03:01:38Z

Regarding directory structure, are we going to flatten all sub crates that are re-exported from jj-lib?

cli/ core/ lib/ gen-protos/ testutils/ ?? git-backend/ ...

or put them under lib/ as before?

cli/ lib/core/ lib/gen-protos/ lib/testutils/ lib/git-backend/ lib/...

Just wondering. I don't have a preference either way.

I guess this is more a question for @martinvonz. I'd prefer to move to a crates/ directory at some point but Martin said that he prefers the flat structure for now.

or put them under lib/ as before?

I like this better. Then the crate name could be jj- followed by the path segments joined by -, e.g. jj-cli, jj-lib-core, jj-lib-gen-protos. What do you think?

IMO, I can do that although I'd prefer if we didn't prefix lib path to the name since these crates should be quite independent of jj-lib.

I think that actually sounds good to me. I was thinking that things like jj-gen-protos sounded too generic, but gen-protos/ will presumably be split up and go into local-working-copy/gen-protos/, simple-op-store/gen-protos/ etc.

Looking at this PR again, I was confused why the new crate is under lib/. As you said, jj-core is supposed to be independent of jj-lib, so it seems to me like it shouldn't be under lib/. I think my previous concern was just about gen-protos/ and testutils/, but I think the answer is that we have core/, lib/ and core/testutils/ (if useful) and lib/testutils/. I think the crate names should match the directory path (with an implied jj-). Does that make sense?

So you still prefer variant 1 of #9766 (comment) if I'm understanding correctly? Then I'll need to move everything back again.

I think I prefer a mix of them:

cli/ core/ core/testutils/ git-commit-backend/ lib/ lib/testutils/ local-working-copy/ local-working-copy/gen-protos/ simple-op-store/ simple-op-store/gen-protos/ ...

Do you follow what I mean? What do you (all) think?

Do you follow what I mean?

yes, thanks for clarifying.

What do you (all) think?

I still don't have any strong opinion on the structure. And I would guess the same for Yuya but he should speak for himself.

pksunkara

I think str_util, time_util needs to be moved too.

martinvonz · 2026-07-08T15:29:27Z

I think str_util, time_util needs to be moved too.

I think the idea is to move most (?) of jj-lib. This is just a first PR.

pksunkara · 2026-07-08T17:30:28Z

👍 If we are doing this incrementally and merge this PR first, I will send the PR to move str_util and time_util and any other things I get to do in the meanwhile.

martinvonz · 2026-07-29T16:39:09Z

-        assert_ne!(hash(&42i32), hash(&[42i32][..]));
-    }
-
+    // TODO: move this over when we lower `hex_util.rs`


why not move hex_util.rs before anything else? it looks like it doesn't depend on anything else

This will be common base for building upon `jj` if you only want the internals which make the other systems work, like the `Backend` or `WorkingCopy` trait. It should be of utmost importance to make the crate as low dependency as possible so its not in the critical path during compilation. Part of #6284

This part of the library is quite basic and it doesn't have too many dependencies which also need to move to make it happen. We also need to move the `ContentHash` macro since all `RepoPath` types depend on it, the macro is moved to a new `jj-core-proc-macros` crate which mirrors the existing structure in `jj-lib`. Since we now have `jj-core-proc-macros` this also deprecates `jj-lib-proc-macros` for external consumers. Part of #6284

As requested by Martin.

This is in preparation of moving `Backend`, `Index` and `Store`. I've also added the `Nothing/EverythingMatcher` even though it's a clear layering violation but I've granted myself an exception for that since they're quite basic. Its a simple move since it only depends on `RepoPathBuf` which already is in the new core crate. Part of #6284

This moves the first interface into the new core library. This also moves the `Signer` struct by dropping the `Config` dependency, to preserve the `jj-lib` API it is imported as `CoreSigner`. Part of #6284

Move the pest grammar, the parser and all DSL related parts to the new crate. Its needed so we can move the `WorkspaceName` and `WorkspaceNameBuf` newtypes for the `WorkingCopyStore` trait. See the next patch. Part of #6284

So `jj-core` users also have access to it, since we already did the same thing for the `RevsetParser`. This is part of building a new `jj-core` crate. Part of #6284

Moving this is quite simple and adds another trait to the core crate. Part of #6284

martinvonz · 2026-08-01T04:49:55Z

It seems weird to leave behind a repo_path module without RepoPath. I sent #9893 to make this more clean.

PhilipMetzger requested a review from a team as a code owner July 6, 2026 16:03

PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch 5 times, most recently from 9234b2b to 951ed8a Compare July 6, 2026 17:58

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Comment thread lib/core/src/lib.rs

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Comment thread lib/core/proc-macros/src/content_hash.rs

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Comment thread lib/src/matchers.rs

pksunkara mentioned this pull request Jul 7, 2026

meta: Extract revset parser as a separate crate #9739

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yuja reviewed Jul 7, 2026

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PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch from ba29d5d to ef577d6 Compare July 7, 2026 21:49

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PhilipMetzger changed the title ~~Add a jj-core crate~~ Add the jj-core crate Jul 8, 2026

martinvonz reviewed Jul 10, 2026

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Comment thread lib/core/proc-macros/src/content_hash.rs

Comment thread lib/core/src/repo_path.rs

Comment thread Cargo.lock

Comment thread lib/src/ref_name.rs Outdated

PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch from ef577d6 to 878837b Compare July 15, 2026 16:44

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Comment thread lib/core/proc-macros/src/content_hash.rs

Comment thread lib/proc-macros/src/lib.rs Outdated

Comment thread lib/core/src/content_hash.rs

PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch 2 times, most recently from 06e5493 to 82455c9 Compare July 16, 2026 20:45

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martinvonz reviewed Jul 30, 2026

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PhilipMetzger added 4 commits July 31, 2026 19:56

core: complete the documentation for repo_path and file_util

54d87da

As requested by Martin.

PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch 2 times, most recently from a9a1b10 to 3c50ef1 Compare July 31, 2026 21:58

PhilipMetzger added 4 commits August 1, 2026 00:00

core: Lower SigningBackend and its related utilities

0ce1b3c

This moves the first interface into the new core library. This also moves the `Signer` struct by dropping the `Config` dependency, to preserve the `jj-lib` API it is imported as `CoreSigner`. Part of #6284

core: Lower all Revset related utilities to it

a66c26a

Move the pest grammar, the parser and all DSL related parts to the new crate. Its needed so we can move the `WorkspaceName` and `WorkspaceNameBuf` newtypes for the `WorkingCopyStore` trait. See the next patch. Part of #6284

core: Move the FilesetParser to it

ad19c71

So `jj-core` users also have access to it, since we already did the same thing for the `RevsetParser`. This is part of building a new `jj-core` crate. Part of #6284

core: Lower the WorkspaceStore into the crate

020d847

Moving this is quite simple and adds another trait to the core crate. Part of #6284

PhilipMetzger force-pushed the pm/xuotnqsxlkpx branch from 3c50ef1 to 020d847 Compare July 31, 2026 22:00

martinvonz reviewed Aug 1, 2026

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PhilipMetzger commented Jul 6, 2026

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martinvonz commented Jul 8, 2026

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martinvonz Aug 1, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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martinvonz Aug 1, 2026 •

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