#2780 introduced method for splitting fqn to class and subname

plugin/core/src/main/java/com/perl5/lang/perl/util/PerlPackageUtil.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2023 Alexandr Evstigneev
+ * Copyright 2015-2024 Alexandr Evstigneev
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,7 @@
 import com.intellij.openapi.fileTypes.FileType;
 import com.intellij.openapi.progress.ProgressManager;
 import com.intellij.openapi.project.Project;
+import com.intellij.openapi.util.NlsSafe;
 import com.intellij.openapi.util.Pair;
 import com.intellij.openapi.util.TextRange;
 import com.intellij.openapi.util.text.StringUtil;
@@ -236,6 +237,24 @@ public static String getCanonicalNamespaceName(@NotNull String name) {
     return packageName == null ? Collections.emptyList() : StringUtil.split(getCanonicalNamespaceName(packageName), NAMESPACE_SEPARATOR);
   }
 
+  @Contract("null -> null")
+  public static @Nullable @NlsSafe Pair<@Nullable String, @Nullable String> splitNames(@Nullable @NlsSafe String fqn) {
+    if (fqn == null || fqn.isEmpty()) {
+      return null;
+    }
+    if (fqn.endsWith(NAMESPACE_SEPARATOR)) {
+      return Pair.create(getCanonicalName(fqn), null);
+    }
+    var sepIndex = fqn.lastIndexOf(NAMESPACE_SEPARATOR);
+    if (sepIndex < 0) {
+      return Pair.create(null, fqn);
+    }
+    if (sepIndex == 0) {
+      return Pair.create(MAIN_NAMESPACE_NAME, fqn.substring(NAMESPACE_SEPARATOR.length()));
+    }
+    return Pair.create(fqn.substring(0, sepIndex), fqn.substring(sepIndex + NAMESPACE_SEPARATOR.length()));
+  }
+
   /**
    * Searching of namespace element is in. If no explicit namespaces defined, main is returned
    *

plugin/src/test/java/unit/perl/PerlPackageUtilTest.java

@@ -0,0 +1,70 @@
+/*
+ * Copyright 2015-2024 Alexandr Evstigneev
+ *
+ * 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
+ *
+ * http://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 unit.perl;
+
+import base.PerlLightTestCase;
+import com.intellij.testFramework.Parameterized;
+import com.perl5.lang.perl.util.PerlPackageUtil;
+import org.jetbrains.annotations.Nullable;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import java.util.Arrays;
+import java.util.Collections;
+
+@SuppressWarnings("Junit4RunWithInspection")
+@RunWith(Parameterized.class)
+public class PerlPackageUtilTest extends PerlLightTestCase {
+  private final @Nullable String myFqn;
+  private final @Nullable String myPackageName;
+  private final @Nullable String mySubName;
+
+  public PerlPackageUtilTest(@Nullable String fqn, @Nullable String packageName, @Nullable String subName) {
+    myFqn = fqn;
+    myPackageName = packageName;
+    mySubName = subName;
+  }
+
+  @Test
+  public void test() {
+    var result = PerlPackageUtil.splitNames(myFqn);
+    if (myFqn == null || myFqn.isEmpty()) {
+      assertNull(result);
+    }
+    else {
+      assertNotNull(result);
+      assertEquals(myPackageName, result.getFirst());
+      assertEquals(mySubName, result.getSecond());
+    }
+  }
+
+  @org.junit.runners.Parameterized.Parameters(name = "{0}")
+  public static Iterable<Object[]> fakeData() {
+    return Collections.emptyList();
+  }
+
+  @Parameterized.Parameters(name = "{0}")
+  public static Iterable<Object[]> realData(Class<?> clazz) {
+    return Arrays.asList(new Object[][]{
+      {null, null, null},
+      {"", null, null},
+      {"::subname", "main", "subname"},
+      {"Foo::", "Foo", null},
+      {"Foo::subname", "Foo", "subname"},
+    });
+  }
+}