emezeske/lein-cljsbuild

Trivial change in CLJC file causes recompile of all CLJS files

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#457 opened on Jan 19, 2017

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Help Wanted

Description

In a fairly large project I am working on, I have a separate source folder with .CLJC-files that are shared between the frontend (Clojurescript) and backend (Clojure).

I noticed that making a trivial change in a CLJC file (e.g., adding a blankline) causes all or most of the CLJC + Clojurescript files to be rebuilt. (See my question on http://stackoverflow.com/questions/41729871/changing-one-cljc-file-causes-full-recompile)

After further investigation, it appears that this problem is not caused by the specifics of my project, but is instead the way lein-cljsbuild intends to operate, to err on the side of safety. (see also https://github.com/emezeske/lein-cljsbuild/issues/345)

Even so, the end result is almost unworkable for me, because trivial changes to CLJC-files cause 45-second builds.

Wouldn't it be a good idea to add an option where the user can specify which (sub)folders in the source code contain "safe" CLJC files? Or, alternatively, an option to treat changes to CLJC-files as changes to CLJS-files (= only recompiles of directly impacted CLJS files), instead of changes to CLJ files (= fully codebase recompiles)?

Figwheel uses a similar configuration option:

:reload-clj-files {:clj true :cljc false}

Contributor guide

Tech stack
None
Domain
build systemtooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
Understanding of ClojureScript compilationFamiliarity with lein cljsbuild source code
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate how lein cljsbuild currently handles .cljc file changes and determines recompilation. Look at the source code, particularly the file watcher and compiler logic, to understand why changes trigger full rebuild. Consider implementing a configuration option similar to Figwheel's `:reload clj files` that allows users to specify behavior for .cljc files. Reference related issue #345 and available configuration patterns in the Figwheel project.