Add integration test for resolving Guava with Gradle

- only using POM metadata (Gradle 5)
- using Gradle Module Metadata (Gradle 6)

integration-tests/gradle/.gitignore

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+.gradle
+build

integration-tests/gradle/build.gradle.kts

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+val expectedReducedRuntimeClasspathJava6 = setOf(
+        "guava-HEAD-android-SNAPSHOT.jar",
+        "failureaccess-1.0.1.jar"
+)
+val expectedReducedRuntimeClasspathJava8 = setOf(
+        "guava-HEAD-jre-SNAPSHOT.jar",
+        "failureaccess-1.0.1.jar"
+)
+val expectedCompileClasspathJava6 = expectedReducedRuntimeClasspathJava6 + setOf(
+        "jsr305-3.0.2.jar",
+        "checker-compat-qual-2.5.5.jar",
+        "error_prone_annotations-2.3.4.jar",
+        "j2objc-annotations-1.3.jar"
+)
+val expectedCompileClasspathJava8 = expectedReducedRuntimeClasspathJava8 + setOf(
+        "jsr305-3.0.2.jar",
+        "checker-qual-2.11.1.jar",
+        "error_prone_annotations-2.3.4.jar",
+        "j2objc-annotations-1.3.jar"
+)
+
+val extraLegacyDependencies = setOf(
+        "listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar",
+        "google-collections-1.0.jar"
+)
+
+subprojects {
+    apply(plugin = "java-library")
+
+    val expectedClasspath =
+        if (gradle.gradleVersion.startsWith("5.")) {
+            // without Gradle Module Metadata (only the POM is used)
+            // - variant decission is made based on version suffix (android/jre) and not on actual Java version
+            // - runtime classpath equals the compile classpath
+            // - dependency conflict with Google Collections is not detected and '9999.0' hack is present
+            if (name.startsWith("android")) {
+                expectedCompileClasspathJava6 + extraLegacyDependencies
+            } else {
+                expectedCompileClasspathJava8 + extraLegacyDependencies
+            }
+        } else {
+            // with Gradle Module Metadata
+            // - variant is choosend based on Java version used independent of version suffix
+            // - reduced runtime classpath is used (w/o annotation libraries)
+            // - capability conflicts are detected between Google Collections and Listenablefuture
+            if (name.contains("Java6")) {
+                if (name.contains("runtimeClasspath")) {
+                    expectedReducedRuntimeClasspathJava6
+                } else {
+                    expectedCompileClasspathJava6
+                }
+            } else {
+                if (name.contains("runtimeClasspath")) {
+                    expectedReducedRuntimeClasspathJava8
+                } else {
+                    expectedCompileClasspathJava8
+                }
+            }
+        }
+    val guavaVersion = if (name.startsWith("jre")) {
+        "HEAD-jre-SNAPSHOT"
+    } else {
+        "HEAD-android-SNAPSHOT"
+    }
+    val javaVersion = if (name.contains("Java6")) {
+        JavaVersion.VERSION_1_6
+    } else {
+        JavaVersion.VERSION_1_8
+    }
+    val classpathConfiguration = if (name.contains("runtimeClasspath")) {
+        configurations["runtimeClasspath"]
+    } else {
+        configurations["compileClasspath"]
+    }
+
+    repositories {
+        mavenCentral()
+        mavenLocal()
+    }
+    val java = extensions.getByType<JavaPluginExtension>()
+    java.targetCompatibility = javaVersion
+    java.sourceCompatibility = javaVersion
+
+    if (!gradle.gradleVersion.startsWith("5.")) {
+        configurations.all {
+            resolutionStrategy.capabilitiesResolution {
+                withCapability("com.google.collections:google-collections") {
+                    candidates.find {
+                        val idField = it.javaClass.getDeclaredMethod("getId") // reflective access to make this compile with Gradle 5
+                        (idField.invoke(it) as ModuleComponentIdentifier).module == "guava"
+                    }?.apply {
+                        select(this)
+                    }
+                }
+                withCapability("com.google.guava:listenablefuture") {
+                    candidates.find {
+                        val idField = it.javaClass.getDeclaredMethod("getId") // reflective access to make this compile with Gradle 5
+                        (idField.invoke(it) as ModuleComponentIdentifier).module == "guava"
+                    }?.apply {
+                        select(this)
+                    }
+                }
+            }
+        }
+    }
+
+    dependencies {
+        "api"("com.google.collections:google-collections:1.0")
+        "api"("com.google.guava:listenablefuture:1.0")
+        "api"("com.google.guava:guava:$guavaVersion")
+    }
+
+    tasks.register("testClasspath") {
+        doLast {
+            val actualClasspath = classpathConfiguration.files.map { it.name }.toSet()
+            if (actualClasspath != expectedClasspath) {
+                throw RuntimeException("""
+                    Expected: ${expectedClasspath.sorted()}
+                    Actual:   ${actualClasspath.sorted()}
+                """.trimIndent())
+            }
+        }
+    }
+}

integration-tests/gradle/gradle/wrapper/gradle-wrapper.properties

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+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.0.1-bin.zip
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

integration-tests/gradle/gradlew

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+#!/usr/bin/env sh
+
+#
+# Copyright 2015 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+##
+##  Gradle start up script for UN*X
+##
+##############################################################################
+
+# Attempt to set APP_HOME
+# Resolve links: $0 may be a link
+PRG="$0"
+# Need this for relative symlinks.
+while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+        PRG="$link"
+    else
+        PRG=`dirname "$PRG"`"/$link"
+    fi
+done
+SAVED="`pwd`"
+cd "`dirname \"$PRG\"`/" >/dev/null
+APP_HOME="`pwd -P`"
+cd "$SAVED" >/dev/null
+
+APP_NAME="Gradle"
+APP_BASE_NAME=`basename "$0"`
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD="maximum"
+
+warn () {
+    echo "$*"
+}
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+}
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "`uname`" in
+  CYGWIN* )
+    cygwin=true
+    ;;
+  Darwin* )
+    darwin=true
+    ;;
+  MINGW* )
+    msys=true
+    ;;
+  NONSTOP* )
+    nonstop=true
+    ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+        JAVACMD="$JAVA_HOME/bin/java"
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD="java"
+    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+fi
+
+# Increase the maximum file descriptors if we can.
+if [ "$cygwin" = "false" -a "$darwin" = "false" -a "$nonstop" = "false" ] ; then
+    MAX_FD_LIMIT=`ulimit -H -n`
+    if [ $? -eq 0 ] ; then
+        if [ "$MAX_FD" = "maximum" -o "$MAX_FD" = "max" ] ; then
+            MAX_FD="$MAX_FD_LIMIT"
+        fi
+        ulimit -n $MAX_FD
+        if [ $? -ne 0 ] ; then
+            warn "Could not set maximum file descriptor limit: $MAX_FD"
+        fi
+    else
+        warn "Could not query maximum file descriptor limit: $MAX_FD_LIMIT"
+    fi
+fi
+
+# For Darwin, add options to specify how the application appears in the dock
+if $darwin; then
+    GRADLE_OPTS="$GRADLE_OPTS \"-Xdock:name=$APP_NAME\" \"-Xdock:icon=$APP_HOME/media/gradle.icns\""
+fi
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if [ "$cygwin" = "true" -o "$msys" = "true" ] ; then
+    APP_HOME=`cygpath --path --mixed "$APP_HOME"`
+    CLASSPATH=`cygpath --path --mixed "$CLASSPATH"`
+    JAVACMD=`cygpath --unix "$JAVACMD"`
+
+    # We build the pattern for arguments to be converted via cygpath
+    ROOTDIRSRAW=`find -L / -maxdepth 1 -mindepth 1 -type d 2>/dev/null`
+    SEP=""
+    for dir in $ROOTDIRSRAW ; do
+        ROOTDIRS="$ROOTDIRS$SEP$dir"
+        SEP="|"
+    done
+    OURCYGPATTERN="(^($ROOTDIRS))"
+    # Add a user-defined pattern to the cygpath arguments
+    if [ "$GRADLE_CYGPATTERN" != "" ] ; then
+        OURCYGPATTERN="$OURCYGPATTERN|($GRADLE_CYGPATTERN)"
+    fi
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    i=0
+    for arg in "$@" ; do
+        CHECK=`echo "$arg"|egrep -c "$OURCYGPATTERN" -`
+        CHECK2=`echo "$arg"|egrep -c "^-"`                                 ### Determine if an option
+
+        if [ $CHECK -ne 0 ] && [ $CHECK2 -eq 0 ] ; then                    ### Added a condition
+            eval `echo args$i`=`cygpath --path --ignore --mixed "$arg"`
+        else
+            eval `echo args$i`="\"$arg\""
+        fi
+        i=$((i+1))
+    done
+    case $i in
+        (0) set -- ;;
+        (1) set -- "$args0" ;;
+        (2) set -- "$args0" "$args1" ;;
+        (3) set -- "$args0" "$args1" "$args2" ;;
+        (4) set -- "$args0" "$args1" "$args2" "$args3" ;;
+        (5) set -- "$args0" "$args1" "$args2" "$args3" "$args4" ;;
+        (6) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" ;;
+        (7) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" ;;
+        (8) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" ;;
+        (9) set -- "$args0" "$args1" "$args2" "$args3" "$args4" "$args5" "$args6" "$args7" "$args8" ;;
+    esac
+fi
+
+# Escape application args
+save () {
+    for i do printf %s\\n "$i" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/' \\\\/" ; done
+    echo " "
+}
+APP_ARGS=$(save "$@")
+
+# Collect all arguments for the java command, following the shell quoting and substitution rules
+eval set -- $DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS "\"-Dorg.gradle.appname=$APP_BASE_NAME\"" -classpath "\"$CLASSPATH\"" org.gradle.wrapper.GradleWrapperMain "$APP_ARGS"
+
+# by default we should be in the correct project dir, but when run from Finder on Mac, the cwd is wrong
+if [ "$(uname)" = "Darwin" ] && [ "$HOME" = "$PWD" ]; then
+  cd "$(dirname "$0")"
+fi
+
+exec "$JAVACMD" "$@"