create script to check for backwards compatibility

.github/workflows/backwards_compatibility_check.sh

@@ -0,0 +1,57 @@
+#!/bin/bash
+
+TRUE=1
+FALSE=0
+
+REMOVED_PACKAGES_FLAG=$FALSE
+REMOVED_METHODS_FLAG=$FALSE
+
+KCL_MAVEN_DIR=~/.m2/repository/software/amazon/kinesis/amazon-kinesis-client
+
+#  clear the Maven directory so that the latest release will be the only version in the Maven directory after running mvn dependency:get
+rm -rf $KCL_MAVEN_DIR
+mvn dependency:get -Dartifact=software.amazon.kinesis:amazon-kinesis-client:LATEST
+LATEST_VERSION=$(ls $KCL_MAVEN_DIR | grep '[0-9].[0-9].[0-9]')
+LATEST_JAR=$KCL_MAVEN_DIR/$LATEST_VERSION/amazon-kinesis-client-$LATEST_VERSION.jar
+
+# get the current jar (i.e. the jar that is pending review)
+mvn install -DskipTests
+CURRENT_VERSION=$(mvn -q  -Dexec.executable=echo -Dexec.args='${project.version}' --non-recursive exec:exec)
+CURRENT_JAR=$KCL_MAVEN_DIR/$CURRENT_VERSION/amazon-kinesis-client-$CURRENT_VERSION.jar
+
+echo "Comparing KCL versions $LATEST_VERSION (latest release) to $CURRENT_VERSION (current)."
+
+# check if any packages were removed
+echo "Checking if packages in version $LATEST_VERSION were removed in $CURRENT_VERSION"
+LATEST_PACKAGES=$(jar tf $LATEST_JAR | grep .class | tr / . |  sed 's/\.class$//' | sort)
+CURRENT_PACKAGES=$(jar tf $CURRENT_JAR | grep .class | tr / . |  sed 's/\.class$//' | sort)
+diff <(echo "$LATEST_PACKAGES") <(echo "$CURRENT_PACKAGES") | grep '^<' && REMOVED_PACKAGES_FLAG=$TRUE || echo "No packages removed in version $CURRENT_VERSION."
+
+# check if any methods within the packages were removed
+echo "Checking if methods in $LATEST_VERSION were removed in $CURRENT_VERSION"
+for package in $CURRENT_PACKAGES
+do
+  # Get the second line of the output which indicates whether a class is public. Only classes that
+  # are public should be checked; other classes will not break backwards compatibility.
+  CLASS_DEFINITION=$(javap -classpath $LATEST_JAR $package | head -2 | tail -1)
+  if [[ $CLASS_DEFINITION != *"public"* ]]
+  then
+    continue
+  fi
+
+  # check if any methods were removed
+  LATEST_METHODS=$(javap -classpath $LATEST_JAR $package)
+  CURRENT_METHODS=$(javap -classpath $CURRENT_JAR $package)
+  diff <(echo "$LATEST_METHODS") <(echo "$CURRENT_METHODS") | grep '^<' && REMOVED_METHODS_FLAG=$TRUE || :
+done
+
+if [[ $REMOVED_METHODS_FLAG == $FALSE ]]
+then
+  echo "No methods removed in version $CURRENT_VERSION."
+fi
+
+if [[ $REMOVED_PACKAGES_FLAG == $TRUE || $REMOVED_METHODS_FLAG == $TRUE ]]
+then
+  echo "KCL version $CURRENT_VERSION is not backwards compatible with version $LATEST_VERSION. See output above for removed packages/methods."
+  exit 1
+fi

.github/workflows/maven.yml

@@ -12,6 +12,7 @@ on:
   push:
     branches:
       - "master"
+      - "bwc"
   pull_request:
     branches:
       - "master"
@@ -29,4 +30,18 @@ jobs:
           java-version: '8'
           distribution: 'corretto'
       - name: Build with Maven
-        run: mvn -B package --file pom.xml -DskipITs
+        run: mvn -B package --file pom.xml -DskipITs
+
+  backwards-compatible-check:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+      - name: Set up JDK 8
+        uses: actions/setup-java@v3
+        with:
+          java-version: '8'
+          distribution: 'corretto'
+      - name: Check backwards compatibility of changes
+        run: .github/workflows/backwards_compatibility_check.sh