build.gradle: Add checkForUpdates task

build.gradle

@@ -1,4 +1,6 @@
 plugins {
+    id 'java' // changes the behavior of TARGET_JVM_VERSION_ATTRIBUTE
+
     id "com.google.osdetector" apply false
     id "me.champeau.gradle.japicmp" apply false
     id "net.ltgt.errorprone" apply false
@@ -524,3 +526,67 @@ def requireUpperBoundDepsMatch(Configuration conf, Project project) {
         }
     }
 }
+
+repositories {
+    mavenCentral()
+    google()
+}
+
+def isAcceptableVersion(ModuleComponentIdentifier candidate) {
+    String group = candidate.group
+    String module = candidate.module
+    String version = candidate.version
+    if (group == 'com.google.guava')
+        return true
+    if (group == 'io.netty' && version.contains('Final'))
+        return true
+    if (module == 'android-api-level-19')
+        return true
+    return version ==~ /^[0-9]+(\.[0-9]+)+$/
+}
+
+configurations {
+    checkForUpdates {
+        attributes.attribute(TargetJvmVersion.TARGET_JVM_VERSION_ATTRIBUTE, 8)
+        resolutionStrategy {
+            componentSelection {
+                all {
+                    if (!isAcceptableVersion(it.candidate))
+                        it.reject("Not stable version")
+                }
+            }
+        }
+    }
+}
+
+// Checks every dependency in the version catalog to see if there is a newer
+// version available. The 'checkForUpdates' configuration restricts the
+// versions considered.
+tasks.register('checkForUpdates') {
+    doLast {
+        def updateConf = project.configurations.checkForUpdates
+        updateConf.setVisible(false)
+        updateConf.setTransitive(false)
+        def versionCatalog = project.extensions.getByType(VersionCatalogsExtension).named("libs")
+        versionCatalog.libraryAliases.each { name ->
+            def dep = versionCatalog.findLibrary(name).get().get()
+
+            def oldConf = updateConf.copy()
+            def oldDep = project.dependencies.create(
+                group: dep.group, name: dep.name, version: dep.versionConstraint, classifier: 'pom')
+            oldConf.dependencies.add(oldDep)
+            def oldResolved = oldConf.resolvedConfiguration.resolvedArtifacts.iterator().next()
+
+            def newConf = updateConf.copy()
+            def newDep = project.dependencies.create(
+                group: dep.group, name: dep.name, version: '+', classifier: 'pom')
+            newConf.dependencies.add(newDep)
+            def newResolved = newConf.resolvedConfiguration.resolvedArtifacts.iterator().next()
+            if (oldResolved != newResolved) {
+                def oldId = oldResolved.id.componentIdentifier
+                def newId = newResolved.id.componentIdentifier
+                println("${newId.group}:${newId.module} ${oldId.version} -> ${newId.version}")
+            }
+        }
+    }
+}