moduleNamePrefixToGroup mapping uses best fit instead of first match

Fixes #90

Author: jjohannes

src/main/java/org/gradlex/javamodule/dependencies/JavaModuleDependenciesExtension.java

@@ -183,7 +183,7 @@ private Provider<String> mapByPrefix(Provider<String> moduleName) {
         return getModuleNamePrefixToGroup().map(
                 m -> {
                     Optional<Map.Entry<String, String>> prefixToGroup = m.entrySet().stream()
-                            .filter(e -> moduleName.get().startsWith(e.getKey())).findFirst();
+                            .filter(e -> moduleName.get().startsWith(e.getKey())).max(Comparator.comparingInt(e -> e.getKey().length()));
                     if (prefixToGroup.isPresent()) {
                         String group = prefixToGroup.get().getValue();
                         String artifact = toProjectName(moduleName.get().substring(prefixToGroup.get().getKey().length()));

src/test/groovy/org/gradlex/javamodule/dependencies/test/GroupMappingTest.groovy

@@ -0,0 +1,43 @@
+package org.gradlex.javamodule.dependencies.test
+
+import org.gradle.testkit.runner.TaskOutcome
+import org.gradlex.javamodule.dependencies.test.fixture.GradleBuild
+import spock.lang.Specification
+
+class GroupMappingTest extends Specification {
+
+    @Delegate
+    GradleBuild build = new GradleBuild()
+
+    def "can map overlapping groups"() {
+        given:
+        def lib2ModuleInfoFile = file("lib-b/src/main/java/module-info.java")
+        def lib2BuildFile = file("lib-b/build.gradle.kts") << libBuildFile.text
+        settingsFile << 'include("lib-b")'
+
+        libModuleInfoFile << 'module com.lib { }'
+        libBuildFile << 'group = "com.foo"'
+        lib2ModuleInfoFile << 'module com.example.lib.b { }'
+        lib2BuildFile << 'group = "com.example"'
+        appModuleInfoFile << '''
+            module org.gradlex.test.app {
+                requires com.lib;
+                requires com.example.lib.b;
+            }
+        '''
+
+        appBuildFile << '''
+            javaModuleDependencies {
+                moduleNamePrefixToGroup.put("com.", "com.foo")
+                moduleNamePrefixToGroup.put("com.example.", "com.example")
+            }
+        '''
+
+        when:
+        def result = runner('assemble').build()
+
+        then:
+        result.task(":app:compileJava").outcome == TaskOutcome.SUCCESS
+    }
+
+}