Determine the minimum gradle version based on the wrapper (#32226)

* Determine the minimum gradle version based on the wrapper

This is restrictive and forces users of the plugin to move together with
us, but without integration tests it's close to impossible to make sure
that the claimed compatability is really there.
If we do want to offer more flexibility, we should add those tests
first.

* Track gradle version in individual file

* PR review

build.gradle

@@ -16,21 +16,17 @@
  * specific language governing permissions and limitations
  * under the License.
  */
-
 import com.github.jengelman.gradle.plugins.shadow.ShadowPlugin
-import org.apache.tools.ant.taskdefs.condition.Os
-import org.apache.tools.ant.filters.ReplaceTokens
 import org.elasticsearch.gradle.BuildPlugin
 import org.elasticsearch.gradle.LoggedExec
 import org.elasticsearch.gradle.Version
 import org.elasticsearch.gradle.VersionCollection
 import org.elasticsearch.gradle.VersionProperties
 import org.gradle.plugins.ide.eclipse.model.SourceFolder
-
-import org.gradle.api.tasks.wrapper.Wrapper
-import org.gradle.api.tasks.wrapper.Wrapper.DistributionType
 import org.gradle.util.GradleVersion
 import org.gradle.util.DistributionLocator
+import org.apache.tools.ant.taskdefs.condition.Os
+import org.apache.tools.ant.filters.ReplaceTokens
 
 import java.nio.file.Files
 import java.nio.file.Path
@@ -562,7 +558,7 @@ task run(type: Run) {
 }
 
 wrapper {
-    distributionType = DistributionType.ALL
+    distributionType = 'ALL'
     doLast {
         final DistributionLocator locator = new DistributionLocator()
         final GradleVersion version = GradleVersion.version(wrapper.gradleVersion)
@@ -571,6 +567,10 @@ wrapper {
         final String sha256Sum = new String(sha256Uri.toURL().bytes)
         wrapper.getPropertiesFile() << "distributionSha256Sum=${sha256Sum}\n"
         println "Added checksum to wrapper properties"
+        // Update build-tools to reflect the Gradle upgrade
+        // TODO: we can remove this once we have tests to make sure older versions work.
+        project(':build-tools').file('src/main/resources/minimumGradleVersion').text = gradleVersion
+        println "Updated minimum Gradle Version"
     }
 }
 

buildSrc/build.gradle

@@ -25,8 +25,9 @@ plugins {
 
 group = 'org.elasticsearch.gradle'
 
-if (GradleVersion.current() < GradleVersion.version('4.9')) {
-  throw new GradleException('Gradle 4.9+ is required to build elasticsearch')
+String minimumGradleVersion = file('src/main/resources/minimumGradleVersion').text.trim()
+if (GradleVersion.current() < GradleVersion.version(minimumGradleVersion)) {
+    throw new GradleException("Gradle ${minimumGradleVersion}+ is required to build elasticsearch")
 }
 
 if (JavaVersion.current() < JavaVersion.VERSION_1_8) {

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -20,6 +20,7 @@ package org.elasticsearch.gradle
 
 import com.carrotsearch.gradle.junit4.RandomizedTestingTask
 import com.github.jengelman.gradle.plugins.shadow.ShadowPlugin
+import org.apache.commons.io.IOUtils
 import org.apache.tools.ant.taskdefs.condition.Os
 import org.eclipse.jgit.lib.Constants
 import org.eclipse.jgit.lib.RepositoryBuilder
@@ -53,6 +54,7 @@ import org.gradle.internal.jvm.Jvm
 import org.gradle.process.ExecResult
 import org.gradle.util.GradleVersion
 
+import java.nio.charset.StandardCharsets
 import java.time.ZoneOffset
 import java.time.ZonedDateTime
 /**
@@ -67,8 +69,13 @@ class BuildPlugin implements Plugin<Project> {
                 + 'elasticearch.standalone-rest-test, and elasticsearch.build '
                 + 'are mutually exclusive')
         }
-        if (GradleVersion.current() < GradleVersion.version('4.9')) {
-            throw new GradleException('Gradle 4.9+ is required to use elasticsearch.build plugin')
+        final String minimumGradleVersion
+        InputStream is = getClass().getResourceAsStream("/minimumGradleVersion")
+        try { minimumGradleVersion = IOUtils.toString(is, StandardCharsets.UTF_8.toString()) } finally { is.close() }
+        if (GradleVersion.current() < GradleVersion.version(minimumGradleVersion.trim())) {
+            throw new GradleException(
+                    "Gradle ${minimumGradleVersion}+ is required to use elasticsearch.build plugin"
+            )
         }
         project.pluginManager.apply('java')
         project.pluginManager.apply('carrotsearch.randomized-testing')
@@ -153,14 +160,6 @@ class BuildPlugin implements Plugin<Project> {
             }
             println "  Random Testing Seed   : ${project.testSeed}"
 
-            // enforce Gradle version
-            final GradleVersion currentGradleVersion = GradleVersion.current();
-
-            final GradleVersion minGradle = GradleVersion.version('4.3')
-            if (currentGradleVersion < minGradle) {
-                throw new GradleException("${minGradle} or above is required to build Elasticsearch")
-            }
-
             // enforce Java version
             if (compilerJavaVersionEnum < minimumCompilerVersion) {
                 final String message =

buildSrc/src/main/resources/minimumGradleVersion

@@ -0,0 +1 @@
+4.9