Expand UpgradePluginVersion to support the kotlin plugin (#6570)

* Allow kotlin plugin to be upgraded
Fix bug where `visitVariable` allowed the version to be downgraded

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: Laurens Westerlaken

rewrite-gradle/src/main/java/org/openrewrite/gradle/plugins/UpgradePluginVersion.java

@@ -153,7 +153,12 @@ public J visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx)
                 if (!(pluginArgs.get(0) instanceof J.Literal)) {
                     return m;
                 }
-                String pluginId = literalValue(pluginArgs.get(0));
+                String pluginId;
+                if ("kotlin".equals(((J.MethodInvocation) m.getSelect()).getSimpleName())) {
+                    pluginId = "kotlin";
+                } else {
+                    pluginId = literalValue(pluginArgs.get(0));
+                }
                 if (pluginId == null || !StringUtils.matchesGlob(pluginId, pluginIdPattern)) {
                     return m;
                 }
@@ -162,8 +167,15 @@ public J visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx)
                 try {
                     String currentVersion = literalValue(versionArgs.get(0));
                     if (currentVersion != null) {
-                        String resolvedVersion = new DependencyVersionSelector(metadataFailures, gradleProject, gradleSettings)
-                                .select(new GroupArtifactVersion(pluginId, pluginId + ".gradle.plugin", currentVersion), "classpath", newVersion, versionPattern, ctx);
+                        String resolvedVersion;
+                        if ("kotlin".equals(pluginId)) {
+                            String fullPluginId = String.format("org.jetbrains.%s.%s", pluginId, literalValue(pluginArgs.get(0)));
+                            resolvedVersion = new DependencyVersionSelector(metadataFailures, gradleProject, gradleSettings)
+                                    .select(new GroupArtifactVersion(fullPluginId, fullPluginId + ".gradle.plugin", currentVersion), "classpath", newVersion, versionPattern, ctx);
+                        } else {
+                            resolvedVersion = new DependencyVersionSelector(metadataFailures, gradleProject, gradleSettings)
+                                    .select(new GroupArtifactVersion(pluginId, pluginId + ".gradle.plugin", currentVersion), "classpath", newVersion, versionPattern, ctx);
+                        }
                         acc.pluginIdToNewVersion.put(pluginId, resolvedVersion);
                     } else if (versionArgs.get(0) instanceof G.GString) {
                         G.GString gString = (G.GString) versionArgs.get(0);
@@ -236,7 +248,12 @@ public J visitMethodInvocation(J.MethodInvocation method, ExecutionContext ctx)
                 }
                 assert m.getSelect() != null;
                 List<Expression> pluginArgs = ((J.MethodInvocation) m.getSelect()).getArguments();
-                String pluginId = literalValue(pluginArgs.get(0));
+                String pluginId;
+                if ("kotlin".equals(((J.MethodInvocation) m.getSelect()).getSimpleName())) {
+                    pluginId = "kotlin";
+                } else {
+                    pluginId = literalValue(pluginArgs.get(0));
+                }
                 if (pluginId == null || !StringUtils.matchesGlob(pluginId, pluginIdPattern)) {
                     return m;
                 }
@@ -264,8 +281,15 @@ public J visitVariable(J.VariableDeclarations.NamedVariable variable, ExecutionC
                     String oldVersion = literalValue(initializer);
                     String newVersion = acc.pluginIdToNewVersion.get(acc.versionPropNameToPluginId.get(visited.getSimpleName()));
                     if (newVersion != null && !newVersion.equals(oldVersion)) {
-                        String valueSource = initializer.getValueSource() == null || oldVersion == null ? initializer.getValueSource() : initializer.getValueSource().replace(oldVersion, newVersion);
-                        return visited.withInitializer(initializer.withValueSource(valueSource).withValue(newVersion));
+                        VersionComparator versionComparator = Semver.validate(newVersion, versionPattern).getValue();
+                        if (versionComparator == null) {
+                            return visited;
+                        }
+                        Optional<String> finalVersion = versionComparator.upgrade(oldVersion != null ? oldVersion : "", singletonList(newVersion));
+                        if (finalVersion.isPresent()) {
+                            String valueSource = initializer.getValueSource() == null || oldVersion == null ? initializer.getValueSource() : initializer.getValueSource().replace(oldVersion, newVersion);
+                            return visited.withInitializer(initializer.withValueSource(valueSource).withValue(finalVersion.get()));
+                        }
                     }
                 }
                 return visited;

rewrite-gradle/src/test/java/org/openrewrite/gradle/plugins/UpgradePluginVersionTest.java

@@ -59,6 +59,44 @@ void upgradePlugin() {
         );
     }
 
+    @Test
+    void upgradeKotlinPluginLiteralVersion() {
+        rewriteRun(
+          spec -> spec.recipe(new UpgradePluginVersion("kotlin", "2.3.0", null)),
+          buildGradleKts(
+            """
+              plugins {
+                  kotlin("jvm") version "2.0.0"
+              }
+              """,
+            """
+              plugins {
+                  kotlin("jvm") version "2.3.0"
+              }
+              """
+          )
+        );
+    }
+
+    @Test
+    void upgradeKotlinPlugin() {
+        rewriteRun(
+          spec -> spec.recipe(new UpgradePluginVersion("kotlin", "latest.minor", null)),
+          buildGradleKts(
+            """
+              plugins {
+                  kotlin("jvm") version "2.0.0"
+              }
+              """,
+            """
+              plugins {
+                  kotlin("jvm") version "2.3.0"
+              }
+              """
+          )
+        );
+    }
+
     @Test
     void upgradeGradleSettingsPlugin() {
         rewriteRun(
@@ -127,6 +165,23 @@ void change() {
         );
     }
 
+    @Test
+    void dontDowngradeWhenExactVersionVariable() {
+        rewriteRun(
+          spec -> spec.recipe(new UpgradePluginVersion("org.openrewrite.rewrite", "5.39.9", null)),
+          settingsGradle(
+            """
+              pluginManagement {
+                  plugins {
+                      String v = '5.40.0'
+                      id 'org.openrewrite.rewrite' version v
+                  }
+              }
+              """
+          )
+        );
+    }
+
     @Test
     void pluginManagementPlugin() {
         rewriteRun(