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MalaxMalax
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Use symlinks instead of moving build directory
sbt relies on stable paths for its incremental compilation cache. The buildpack previously moved the entire build directory to a temporary location to provide a stable path, then moved it back at the end. This change replaces the expensive move operations with a symlink, providing the same stable path for sbt while keeping files in their original location. This eliminates the need to rewrite PATH and GEM_PATH variables to account for the directory move.
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2 files changed

+16
-27
lines changed

2 files changed

+16
-27
lines changed

‎bin/compile‎

Lines changed: 3 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -32,22 +32,11 @@ metrics::setup
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3333
if is_app_dir "${APP_BUILD_DIR}"; then
3434
BUILD_DIR="/tmp/scala_buildpack_build_dir"
35-
mv "${APP_BUILD_DIR}" "${BUILD_DIR}"
35+
ln -s "${APP_BUILD_DIR}" "${BUILD_DIR}"
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else
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BUILD_DIR="${APP_BUILD_DIR}"
3838
fi
3939

40-
# When multiple buildpacks are used, earlier buildpacks may add executables to PATH
41-
# and GEM_PATH that reference APP_BUILD_DIR. Since we've moved the build directory to
42-
# a temp location, we must rewrite these environment variables to replace APP_BUILD_DIR
43-
# with the new BUILD_DIR so that executables added by earlier buildpacks remain accessible.
44-
PATH=${PATH//"${APP_BUILD_DIR}"/"${BUILD_DIR}"}
45-
export PATH
46-
if [[ -n "${GEM_PATH:-}" ]]; then
47-
GEM_PATH=${GEM_PATH//"${APP_BUILD_DIR}"/"${BUILD_DIR}"}
48-
export GEM_PATH
49-
fi
50-
5140
util::export_env_dir "${ENV_DIR}" "." "JAVA_OPTS"
5241

5342
# Used by install_jdk to determine which JVM common buildpack to use
@@ -275,9 +264,9 @@ cat <<-EOF >"${profile_script}"
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export PATH="\$SBT_HOME/bin:\$PATH"
276265
EOF
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278-
# Move compiled app back to where Heroku expects it
267+
# Remove symlink if we created one
279268
if is_app_dir "${APP_BUILD_DIR}"; then
280-
mv "${BUILD_DIR}" "${APP_BUILD_DIR}"
269+
rm "${BUILD_DIR}"
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fi
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283272
# write export script

‎test/spec/cache_spec.rb‎

Lines changed: 13 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -13,21 +13,21 @@
1313
remote: -----> Running: sbt compile stage
1414
remote: Downloading sbt launcher for 1.11.7:
1515
remote: From https://repo1.maven.org/maven2/org/scala-sbt/sbt-launch/1.11.7/sbt-launch-1.11.7.jar
16-
remote: To /tmp/scala_buildpack_build_dir/.sbt_home/launchers/1.11.7/sbt-launch.jar
16+
remote: To /tmp/[^/]+/.sbt_home/launchers/1.11.7/sbt-launch.jar
1717
remote: Downloading sbt launcher 1.11.7 md5 hash:
1818
remote: From https://repo1.maven.org/maven2/org/scala-sbt/sbt-launch/1.11.7/sbt-launch-1.11.7.jar.md5
19-
remote: To /tmp/scala_buildpack_build_dir/.sbt_home/launchers/1.11.7/sbt-launch.jar.md5
20-
remote: /tmp/scala_buildpack_build_dir/.sbt_home/launchers/1.11.7/sbt-launch.jar: OK
19+
remote: To /tmp/[^/]+/.sbt_home/launchers/1.11.7/sbt-launch.jar.md5
20+
remote: /tmp/[^/]+/.sbt_home/launchers/1.11.7/sbt-launch.jar: OK
2121
remote: \\[info\\] \\[launcher\\] getting org.scala-sbt sbt 1.11.7 \\(this may take some time\\)...
2222
remote: \\[info\\] \\[launcher\\] getting Scala 2.12.20 \\(for sbt\\)...
2323
remote: \\[info\\] welcome to sbt 1.11.7 \\(Azul Systems, Inc. Java 21.0.[0-9]+\\)
24-
remote: \\[info\\] loading global plugins from /tmp/scala_buildpack_build_dir/.sbt_home/plugins
25-
remote: \\[info\\] compiling 1 Scala source to /tmp/scala_buildpack_build_dir/.sbt_home/plugins/target/scala-2.12/sbt-1.0/classes ...
24+
remote: \\[info\\] loading global plugins from /tmp/[^/]+/.sbt_home/plugins
25+
remote: \\[info\\] compiling 1 Scala source to /tmp/[^/]+/.sbt_home/plugins/target/scala-2.12/sbt-1.0/classes ...
2626
remote: \\[info\\] Non-compiled module 'compiler-bridge_2.12' for Scala 2.12.20. Compiling...
2727
remote: \\[info\\] Compilation completed in .*s.
2828
remote: \\[info\\] done compiling
29-
remote: \\[info\\] loading settings for project scala_buildpack_build_dir-build from plugins.sbt...
30-
remote: \\[info\\] loading project definition from /tmp/scala_buildpack_build_dir/project
29+
remote: \\[info\\] loading settings for project [^\\s]+-build from plugins.sbt...
30+
remote: \\[info\\] loading project definition from /tmp/[^/]+/project
3131
remote: \\[info\\] loading settings for project root from build.sbt...
3232
remote: \\[info\\] __ __
3333
remote: \\[info\\] \\\\ \\\\ ____ / /____ _ __ __
@@ -42,10 +42,10 @@
4242
remote: \\[info\\] https://www.playframework.com/sponsors
4343
remote: \\[info\\]
4444
remote: \\[info\\] Executing in batch mode. For better performance use sbt's shell
45-
remote: \\[info\\] compiling 7 Scala sources and 1 Java source to /tmp/scala_buildpack_build_dir/target/scala-2.13/classes ...
45+
remote: \\[info\\] compiling 7 Scala sources and 1 Java source to /tmp/[^/]+/target/scala-2.13/classes ...
4646
remote: \\[info\\] done compiling
4747
remote: \\[success\\] Total time: .* s, completed .*
48-
remote: \\[info\\] Wrote /tmp/scala_buildpack_build_dir/target/scala-2.13/sbt-0-11-7-play-3-x-scala-2-13-x_2.13-1.0-SNAPSHOT.pom
48+
remote: \\[info\\] Wrote /tmp/[^/]+/target/scala-2.13/sbt-0-11-7-play-3-x-scala-2-13-x_2.13-1.0-SNAPSHOT.pom
4949
remote: \\[success\\] Total time: .*
5050
remote: -----> Collecting dependency information
5151
remote: -----> Dropping ivy cache from the slug
@@ -68,9 +68,9 @@
6868
remote: -----> Installing Azul Zulu OpenJDK 21.0.[0-9]+
6969
remote: -----> Running: sbt compile stage
7070
remote: \\[info\\] welcome to sbt 1.11.7 \\(Azul Systems, Inc. Java 21.0.[0-9]+\\)
71-
remote: \\[info\\] loading global plugins from /tmp/scala_buildpack_build_dir/.sbt_home/plugins
72-
remote: \\[info\\] loading settings for project scala_buildpack_build_dir-build from plugins.sbt...
73-
remote: \\[info\\] loading project definition from /tmp/scala_buildpack_build_dir/project
71+
remote: \\[info\\] loading global plugins from /tmp/[^/]+/.sbt_home/plugins
72+
remote: \\[info\\] loading settings for project [^\\s]+-build from plugins.sbt...
73+
remote: \\[info\\] loading project definition from /tmp/[^/]+/project
7474
remote: \\[info\\] loading settings for project root from build.sbt...
7575
remote: \\[info\\] __ __
7676
remote: \\[info\\] \\\\ \\\\ ____ / /____ _ __ __
@@ -86,7 +86,7 @@
8686
remote: \\[info\\]
8787
remote: \\[info\\] Executing in batch mode. For better performance use sbt's shell
8888
remote: \\[success\\] Total time: .* s, completed .*
89-
remote: \\[info\\] Wrote /tmp/scala_buildpack_build_dir/target/scala-2.13/sbt-0-11-7-play-3-x-scala-2-13-x_2.13-1.0-SNAPSHOT.pom
89+
remote: \\[info\\] Wrote /tmp/[^/]+/target/scala-2.13/sbt-0-11-7-play-3-x-scala-2-13-x_2.13-1.0-SNAPSHOT.pom
9090
remote: \\[success\\] Total time: .*
9191
remote: -----> Collecting dependency information
9292
remote: -----> Dropping ivy cache from the slug

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