diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
new file mode 100644
index 00000000..bb70059a
--- /dev/null
+++ b/CONTRIBUTING.md
@@ -0,0 +1,28 @@
+# How to Contribute
+
+We'd love to accept your patches and contributions to this project. There are
+just a few small guidelines you need to follow.
+
+## Contributor License Agreement
+
+Contributions to this project must be accompanied by a Contributor License
+Agreement. You (or your employer) retain the copyright to your contribution,
+this simply gives us permission to use and redistribute your contributions as
+part of the project. Head over to to see
+your current agreements on file or to sign a new one.
+
+You generally only need to submit a CLA once, so if you've already submitted one
+(even if it was for a different project), you probably don't need to do it
+again.
+
+## Code reviews
+
+All submissions, including submissions by project members, require review. We
+use GitHub pull requests for this purpose. Consult
+[GitHub Help](https://help.github.com/articles/about-pull-requests/) for more
+information on using pull requests.
+
+## Community Guidelines
+
+This project follows [Google's Open Source Community
+Guidelines](https://opensource.google.com/conduct/).
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 00000000..7a4a3ea2
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,202 @@
+
+ Apache License
+ Version 2.0, January 2004
+ http://www.apache.org/licenses/
+
+ TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+ 1. Definitions.
+
+ "License" shall mean the terms and conditions for use, reproduction,
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+ 5. Submission of Contributions. Unless You explicitly state otherwise,
+ any Contribution intentionally submitted for inclusion in the Work
+ by You to the Licensor shall be under the terms and conditions of
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+ END OF TERMS AND CONDITIONS
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+ APPENDIX: How to apply the Apache License to your work.
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+ To apply the Apache License to your work, attach the following
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+ Copyright [yyyy] [name of copyright owner]
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+ Licensed under the Apache License, Version 2.0 (the "License");
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+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
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+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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\ No newline at end of file
diff --git a/README.md b/README.md
new file mode 100644
index 00000000..20f0085e
--- /dev/null
+++ b/README.md
@@ -0,0 +1,26 @@
+# Strict Version Matcher Gradle Plugin
+
+This plugin scans a subset of Google Play services and Firebase dependencies
+during the Bradle build. It raises an error when version resolution is specified
+in the POM file but not honored by the Gradle build system. This can happen when
+Gradle's default dependency resolution strategy is used because it uses the
+highest referenced version even if it crossed the major version boundary.
+
+## To use
+
+In your app's build.gradle:
+
+```
+apply plugin: 'com.google.android.gms.strict-version-matcher-plugin'
+```
+
+In order to use this plugin, you will also need to add the following to your
+buildscript classpath, obtained from Google’s
+[Maven repository](//developer.android.com/studio/build/dependencies#google-maven):
+
+```
+classpath 'com.google.android.gms:strict-version-matcher-plugin:1.0.2'
+```
+
+These instructions are also documented
+[online](//developers.google.com/android/guides/versioning)
diff --git a/build.gradle b/build.gradle
new file mode 100644
index 00000000..29d38d9d
--- /dev/null
+++ b/build.gradle
@@ -0,0 +1,33 @@
+buildscript {
+ repositories {
+ jcenter()
+ }
+ dependencies {
+ }
+}
+
+project.ext.group = 'com.google.android.gms'
+project.ext.archivesBaseName = 'strict-version-matcher-plugin'
+project.ext.version = '1.0.2'
+project.ext.pomDesc = 'Gradle plug-in to enforce version ranges for Google Play services and Firebase dependencies.'
+
+apply plugin: 'groovy'
+
+repositories {
+ jcenter()
+}
+
+dependencies {
+ compile gradleApi()
+ testCompile 'junit:junit:4.12'
+ testCompile "com.google.truth:truth:0.39"
+}
+
+apply from: 'publish.gradle'
+
+if (project.has('bintrayUser') && project.has('bintrayKey')) {
+ apply from: 'bintray.gradle'
+}
+
+sourceCompatibility = 1.7
+targetCompatibility = 1.7
diff --git a/gradle.properties b/gradle.properties
new file mode 100644
index 00000000..66412108
--- /dev/null
+++ b/gradle.properties
@@ -0,0 +1,21 @@
+# Project-wide Gradle settings.
+
+# IDE (e.g. Android Studio) users:
+# Gradle settings configured through the IDE *will override*
+# any settings specified in this file.
+
+# For more details on how to configure your build environment visit
+# http://www.gradle.org/docs/current/userguide/build_environment.html
+
+# Specifies the JVM arguments used for the daemon process.
+# The setting is particularly useful for tweaking memory settings.
+# Default value: -Xmx10248m -XX:MaxPermSize=256m
+org.gradle.jvmargs=-Xmx2048m -XX:MaxPermSize=512m -XX:+HeapDumpOnOutOfMemoryError -Dfile.encoding=UTF-8
+org.gradle.java.home=/usr/local/buildtools/java/jdk8/
+
+# When configured, Gradle will run in incubating parallel mode.
+# This option should only be used with decoupled projects. More details, visit
+# http://www.gradle.org/docs/current/userguide/multi_project_builds.html#sec:decoupled_projects
+org.gradle.parallel=true
+
+org.gradle.daemon=true
diff --git a/src/main/groovy/com/google/android/gms/StrictVersionMatcherPlugin.groovy b/src/main/groovy/com/google/android/gms/StrictVersionMatcherPlugin.groovy
new file mode 100644
index 00000000..bf575353
--- /dev/null
+++ b/src/main/groovy/com/google/android/gms/StrictVersionMatcherPlugin.groovy
@@ -0,0 +1,189 @@
+/**
+ * Copyright 2018 Google LLC
+ *
+ * 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.
+ */
+
+package com.google.android.gms
+
+import java.util.HashSet
+import java.util.HashMap
+import java.util.SortedSet
+import java.util.TreeSet
+import java.util.regex.Matcher
+import java.util.regex.Pattern
+import org.gradle.BuildListener
+import org.gradle.BuildResult
+import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.Dependency
+import org.gradle.api.artifacts.DependencyResolutionListener
+import org.gradle.api.artifacts.ProjectDependency
+import org.gradle.api.artifacts.ResolvableDependencies
+import org.gradle.api.initialization.Settings
+import org.gradle.api.internal.artifacts.dependencies.DefaultProjectDependency
+import org.gradle.api.invocation.Gradle
+import org.gradle.api.GradleException
+import org.gradle.api.Plugin
+import org.gradle.api.Project
+
+class StrictVersionMatcherPlugin implements Plugin {
+ // Some example of things that match this pattern are:
+ // "[1]"
+ // "[10]"
+ // "[10.3.234]"
+ // And here is an example with the capture group 1 in
+ // [<1.2.3.4>]
+ public static final Pattern VERSION_RANGE_PATTERN = ~/\[(\d+(\.\d+)*)\]/
+
+ public static HashMap>> versionsByGroupAndName = new HashMap<>();
+
+ @Override
+ void apply(Project project) {
+ failOnVersionConflictForGroup(project, "com.google.android.gms")
+ failOnVersionConflictForGroup(project, "com.google.firebase")
+ }
+
+ static int versionCompare(String str1, String str2) {
+ String[] vals1 = str1.split("\\.");
+ String[] vals2 = str2.split("\\.");
+ int i = 0;
+ while (i < vals1.length && i < vals2.length && vals1[i].equals(vals2[i])) {
+ i++;
+ }
+ if (i < vals1.length && i < vals2.length) {
+ int diff = Integer.valueOf(vals1[i]).compareTo(Integer.valueOf(vals2[i]));
+ return Integer.signum(diff);
+ }
+ return Integer.signum(vals1.length - vals2.length);
+ }
+
+ /**
+ * Adds two hooks to the build project, the first is when every dependency
+ * is resolved, if it matches the group prefix its requested version is
+ * parsed and stored. The second is hooked in right before compilation, and
+ * checks the resolved dependencies to ensure they match the requested ranges
+ * stored earlier. If a mismatch occurs, a GradleException is thrown.
+ */
+ static void failOnVersionConflictForGroup(Project project, String groupPrefix) {
+ versionsByGroupAndName = new HashMap<>();
+ project.configurations.all {
+ resolutionStrategy.eachDependency { details ->
+ String group = details.requested.group
+ String name = details.requested.name
+ String version = details.requested.version
+ if (group == null || name == null || version == null) {
+ return
+ }
+ if (group.startsWith(groupPrefix)) {
+ if(!versionsByGroupAndName.containsKey(group)) {
+ versionsByGroupAndName.put(group, new HashMap<>())
+ }
+ if(!versionsByGroupAndName.get(group).containsKey(name)) {
+ versionsByGroupAndName.get(group).put(name, new HashSet<>())
+ }
+ VersionRange versionRange = VersionRange.fromString(version)
+ if (versionRange != null) {
+ versionsByGroupAndName.get(group).get(name).add(versionRange)
+ }
+ }
+ }
+ }
+ project.getGradle().addListener(new DependencyResolutionListener() {
+ @Override
+ void beforeResolve(ResolvableDependencies resolvableDependencies) {
+ }
+
+ @Override
+ void afterResolve(ResolvableDependencies resolvableDependencies) {
+ resolvableDependencies.getResolutionResult().allComponents {artifact ->
+ String group = artifact.moduleVersion.group
+ String name = artifact.moduleVersion.name
+ Version version = Version.fromString(artifact.moduleVersion.version)
+ if (group == null || name == null || version == null) {
+ return
+ }
+ if (group.startsWith(groupPrefix)) {
+ HashSet ranges = versionsByGroupAndName
+ .getOrDefault(group, new HashMap())
+ .getOrDefault(name, new HashSet())
+ for (VersionRange range : ranges) {
+ if (!range.versionInRange(version)) {
+ throw new GradleException("The library $group:$name is being requested by "
+ + "various other libraries at $ranges, but resolves to $version.rawVersion. "
+ + "Disable the plugin and check your dependencies tree using ./gradlew :app:dependencies.")
+ }
+ }
+ }
+ }
+ }
+ })
+ }
+
+ @groovy.transform.Immutable static class Version {
+ String rawVersion, trimmedVersion
+ public static Version fromString(String version) {
+ if (version == null) {
+ return null
+ }
+ return new Version(version, version.split("-")[0])
+ }
+ }
+ @groovy.transform.Immutable static class VersionRange {
+ boolean closedStart
+ boolean closedEnd
+ Version rangeStart
+ Version rangeEnd
+
+ public static VersionRange fromString(String versionRange) {
+ Matcher versionRangeMatcher = VERSION_RANGE_PATTERN.matcher(versionRange)
+ if (versionRangeMatcher.matches()) {
+ Version version = Version.fromString(versionRangeMatcher.group(1))
+ return new VersionRange(
+ true,
+ true,
+ version,
+ version)
+ }
+ return null
+ }
+
+ boolean versionInRange(Version version) {
+ if (closedStart) {
+ if (versionCompare(rangeStart.trimmedVersion, version.trimmedVersion) > 0) {
+ return false;
+ }
+ } else {
+ if (versionCompare(rangeStart.trimmedVersion, version.trimmedVersion) >= 0) {
+ return false;
+ }
+ }
+ if (closedEnd) {
+ if (versionCompare(rangeEnd.trimmedVersion, version.trimmedVersion) < 0) {
+ return false;
+ }
+ } else {
+ if (versionCompare(rangeEnd.trimmedVersion, version.trimmedVersion) <= 0) {
+ return false;
+ }
+ }
+ return true;
+ }
+
+ public String toString() {
+ return ((closedStart ? "[" : "(")
+ + rangeStart.trimmedVersion + ","
+ + rangeEnd.trimmedVersion
+ + (closedEnd ? "]" : ")"))
+ }
+ }
+}
diff --git a/src/main/resources/META-INF/gradle-plugins/com.google.android.gms.strict-version-matcher-plugin.properties b/src/main/resources/META-INF/gradle-plugins/com.google.android.gms.strict-version-matcher-plugin.properties
new file mode 100644
index 00000000..a341484b
--- /dev/null
+++ b/src/main/resources/META-INF/gradle-plugins/com.google.android.gms.strict-version-matcher-plugin.properties
@@ -0,0 +1 @@
+implementation-class=com.google.android.gms.StrictVersionMatcherPlugin
diff --git a/src/test/java/com/google/android/gms/StrictVersionMatcherPluginTest.java b/src/test/java/com/google/android/gms/StrictVersionMatcherPluginTest.java
new file mode 100644
index 00000000..59a6d2e5
--- /dev/null
+++ b/src/test/java/com/google/android/gms/StrictVersionMatcherPluginTest.java
@@ -0,0 +1,47 @@
+/**
+ * Copyright 2018 Google LLC
+ *
+ * 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.
+ */
+
+package com.google.android.gms;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.android.gms.StrictVersionMatcherPlugin.Version;
+import com.google.android.gms.StrictVersionMatcherPlugin.VersionRange;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.HashMap;
+import java.util.stream.Collectors;
+import org.gradle.api.GradleException;
+import org.junit.Test;
+
+public class StrictVersionMatcherPluginTest {
+
+ @Test
+ public void testVersionCompare() {
+ assertThat(StrictVersionMatcherPlugin.versionCompare("1.0.0", "2.0.0")).isLessThan(0);
+ assertThat(StrictVersionMatcherPlugin.versionCompare("1.10.1", "1.9.0")).isGreaterThan(0);
+ assertThat(StrictVersionMatcherPlugin.versionCompare("1.0.0", "1.0.0")).isEqualTo(0);
+ }
+
+ @Test
+ public void closedNonRangeVersionRangeTest() {
+ VersionRange range = VersionRange.fromString("[1.2.3]");
+ Version version = Version.fromString("1.2.3-SNAPSHOT");
+ Version highVersion = Version.fromString("5.3.2");
+ assertThat(range.versionInRange(version)).isTrue();
+ assertThat(range.versionInRange(highVersion)).isFalse();
+ }
+}