Use project.el directly for project root detection#3922
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Introduce `cider-project-dir` + `cider-build-tool-files` and migrate all `clojure-project-dir' call sites to use them. Project root detection now goes through `project.el' instead of bouncing through `clojure-mode' or `clojure-ts-mode' wrappers. This: * Decouples cider's project detection from `clojure-mode' (it still needs the package loaded for other reasons, but not for this one). * Works the same whether the buffer is in `clojure-mode', `clojure-ts-mode', or anything else (e.g. running `cider-connect' from Dired). * Respects user customisation of `project-find-functions', `project-vc-extra-root-markers', and friends -- the same semantics clojure-ts-mode already adopted internally. Falls back to `locate-dominating-file' against `cider-build-tool-files' when `project.el' doesn't find anything; that also covers Emacs 28, which doesn't have `project-vc-extra-root-markers'. No caching layer for now -- `project.el's' detection is already cheap in the common case, and adding our own cache would require a clear invalidation story we don't have yet. Easy to revisit if profiling turns up a hot path.
On Emacs 28, project.el doesn't define this variable, so the byte-compiler treats the `let' binding in `cider-project-dir' as an unused lexical variable. Declaring it with a value-less `defvar' tells the compiler it's dynamic without changing runtime behavior.
This was referenced May 20, 2026
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Step 1 of decoupling cider from
clojure-mode/clojure-ts-modefor things that don't actually require either: introducecider-project-dir(built on top ofproject.el) and migrate everyclojure-project-dircall site to it.Why this is better than dispatching between
clojure-project-dirandclojure-ts-project-dir:clojure-project-diruseslocate-dominating-filedirectly, whileclojure-ts-project-dirgoes throughproject.el. The same file can return different roots depending on which major mode is active. One source of truth removes that.clojure-mode,clojure-ts-mode, or any other buffer (e.g.M-x cider-connectfrom Dired).project-find-functions,project-vc-extra-root-markers, etc., the same project.el customization users already have configured for everything else in Emacs.cider-build-tool-filesis appended toproject-vc-extra-root-markersso adeps.edn/project.cljroot wins over a deeper enclosing VC root.locate-dominating-fileagainstcider-build-tool-fileswhenproject.eldoesn't detect anything. That also handles Emacs 28, which doesn't haveproject-vc-extra-root-markers.No caching layer for now.
project.el's detection is already cheap in the common case, and adding a cache would need an invalidation story we don't have yet. Easy follow-up if profiling turns up a hot path.Follow-ups in the same direction (not in this PR):
cider-expected-ns, and migratingcider-get-ns-nameoff theup-list-based path entirely.