Make the build reproducible and add a check

.github/workflows/reproducible-build-check.yml

@@ -0,0 +1,38 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+# This workflow will build a Java project with Gradle and cache/restore any dependencies to improve the workflow execution time
+# For more information see: https://docs.github.com/en/actions/automating-builds-and-tests/building-and-testing-java-with-gradle
+
+name: Java CI Reproducible build check
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up JDK 17
+        uses: actions/setup-java@v3
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@af1da67850ed9a4cedd57bfd976089dd991e2582 # v4.0.0
+      - name: Check artifacts
+        shell: bash
+        run: |
+          ./gradlew --no-daemon clean publishToMavenLocal --no-build-cache -Dmaven.repo.local=${GITHUB_WORKSPACE}/build1
+          ./gradlew --no-daemon clean publishToMavenLocal --no-build-cache -Dmaven.repo.local=${GITHUB_WORKSPACE}/build2
+          ./ci/compare-build-results.sh ${GITHUB_WORKSPACE}/build1 ${GITHUB_WORKSPACE}/build2

buildSrc/src/main/groovy/java-module.gradle

@@ -50,6 +50,12 @@ tasks.withType( JavaCompile ).configureEach {javaCompile->
 	options.warnings false
 }
 
+// To force the build produce the same byte-for-byte archives and hence make Hibernate Models build reproducible.
+// See also https://docs.gradle.org/current/userguide/working_with_files.html#sec:reproducible_archives
+tasks.withType( AbstractArchiveTask ).configureEach {
+	preserveFileTimestamps = false
+	reproducibleFileOrder = true
+}
 
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // Javadoc
@@ -150,4 +156,4 @@ tasks.named( "check" ) {
 	dependsOn enforceRulesTask
 	dependsOn tasks.named( "spotlessCheck" )
 	dependsOn jacocoReportTask
-}
+}

ci/compare-build-results.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+
+# This is a simple script to check if builds are reproducible. The steps are:
+# 1. Build Hibernate Models with `./gradlew --no-daemon clean publishToMavenLocal --no-build-cache -Dmaven.repo.local=some-path/out/build1`
+# 2. Build Hibernate Models with `./gradlew --no-daemon clean publishToMavenLocal --no-build-cache -Dmaven.repo.local=some-path/out/build2` second time pointing to a different local maven repository to publish
+# 3. Compare the build results with sh ./ci/compare-build-results.sh some-path/out/build1 some-path/out/build2
+# 4. The generated .buildcompare file will also contain the diffscope commands to see/compare the problematic build artifacts
+set -xv
+
+outputDir1=$1
+outputDir2=$2
+outputDir1=${outputDir1%/}
+outputDir2=${outputDir2%/}
+
+ok=()
+okFiles=()
+ko=()
+koFiles=()
+
+for f in `find ${outputDir1} -type f | grep -v "javadoc.jar$" | grep -v "maven-metadata-local.xml$" | sort`
+do
+  flocal=${f#$outputDir1}
+  #  echo "comparing ${flocal}"
+  sha1=`shasum -a 512 $f | cut -f 1 -d ' '`
+  sha2=`shasum -a 512 $outputDir2$flocal | cut -f 1 -d ' '`
+  #  echo "$sha1"
+  #  echo "$sha2"
+  if [ "$sha1" = "$sha2" ]; then
+    ok+=($flocal)
+    okFiles+=(${flocal##*/})
+  else
+    ko+=($flocal)
+    koFiles+=(${flocal##*/})
+  fi
+done
+
+# generate .buildcompare
+buildcompare=".buildcompare"
+echo "ok=${#ok[@]}" >> ${buildcompare}
+echo "ko=${#ko[@]}" >> ${buildcompare}
+echo "okFiles=\"${okFiles[@]}\"" >> ${buildcompare}
+echo "koFiles=\"${koFiles[@]}\"" >> ${buildcompare}
+echo "" >> ${buildcompare}
+echo "# see what caused the mismatch in the checksum by executing the following diffscope commands" >> ${buildcompare}
+for f in ${ko[@]}
+do
+  echo "# diffoscope $outputDir1$f $outputDir2$f" >> ${buildcompare}
+done
+
+if [ ${#ko[@]} -eq 0 ]; then
+    exit 0
+else
+   exit 1
+fi