From e7509272b31867c1461d983ddbc49b074ac25adf Mon Sep 17 00:00:00 2001
From: Eric Hanson <5846501+ericphanson@users.noreply.github.com>
Date: Mon, 21 Jul 2025 18:16:15 +0200
Subject: [PATCH] Julia: support language_version

---
 .github/workflows/languages.yaml |  7 ++++++-
 pre_commit/languages/julia.py    |  7 ++++++-
 tests/languages/julia_test.py    | 16 ++++++++++++++++
 3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/.github/workflows/languages.yaml b/.github/workflows/languages.yaml
index fccf2989..e45332ab 100644
--- a/.github/workflows/languages.yaml
+++ b/.github/workflows/languages.yaml
@@ -67,7 +67,12 @@ jobs:
       if: matrix.language == 'haskell'
     - uses: r-lib/actions/setup-r@v2
       if: matrix.os == 'ubuntu-latest' && matrix.language == 'r'
-
+    - uses: julia-actions/install-juliaup@v2
+      if: matrix.language == 'julia'
+      with:
+        channel: 'release'
+    - run: juliaup add 1.10.10
+      if: matrix.language == 'julia'
     - name: install deps
       run: python -mpip install -e . -r requirements-dev.txt
     - name: run tests
diff --git a/pre_commit/languages/julia.py b/pre_commit/languages/julia.py
index df91c069..910eb8eb 100644
--- a/pre_commit/languages/julia.py
+++ b/pre_commit/languages/julia.py
@@ -49,8 +49,13 @@ def run_hook(
 def get_env_patch(target_dir: str, version: str) -> PatchesT:
     return (
         ('JULIA_LOAD_PATH', target_dir),
-        # May be set, remove it to not interfer with LOAD_PATH
+        # May be set, remove it to not interfere with LOAD_PATH
         ('JULIA_PROJECT', UNSET),
+        # Only set JULIAUP_CHANNEL if we don't want use the system's default
+        *(
+            (('JULIAUP_CHANNEL', version),)
+            if version not in ('system', 'default') else ()
+        ),
     )
 
 
diff --git a/tests/languages/julia_test.py b/tests/languages/julia_test.py
index 4ea3c25b..cefd6833 100644
--- a/tests/languages/julia_test.py
+++ b/tests/languages/julia_test.py
@@ -28,6 +28,22 @@ def test_julia_hook(tmp_path):
     assert run_language(tmp_path, julia, 'src/main.jl') == expected
 
 
+def test_julia_hook_version(tmp_path):
+    code = """
+    using Example
+    function main()
+        println("Hello, Julia $(VERSION)!")
+    end
+    main()
+    """
+    _make_hook(tmp_path, code)
+    expected = (0, b'Hello, Julia 1.10.10!\n')
+    assert run_language(
+        tmp_path, julia, 'src/main.jl',
+        version='1.10.10',
+    ) == expected
+
+
 def test_julia_hook_manifest(tmp_path):
     code = """
     using Example