refactor(gradle): Move OrtDependency extension functions to the model

Prepare for reuse and also perform some minor generalizations. As part of
that, hard-code the "Gradle" project type in order to not be dependent on
a package manager instance.

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

plugins/package-managers/gradle-model/src/main/kotlin/Extensions.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2021 The ORT Project Authors (see <https://github.com/oss-review-toolkit/ort/blob/main/NOTICE>)
+ *
+ * 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
+ *
+ *     https://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.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * License-Filename: LICENSE
+ */
+
+package org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel
+
+import OrtDependency
+
+/**
+ * Determine the type of this Gradle dependency. In case of a project, it is "Gradle". Otherwise it is "Maven" unless
+ * there is no POM, then it is "Unknown".
+ */
+fun OrtDependency.dependencyType(): String =
+    if (isProjectDependency()) {
+        "Gradle"
+    } else {
+        pomFile?.let { "Maven" } ?: "Unknown"
+    }
+
+/**
+ * Return true if this Gradle dependency refers to another project, or false if it refers to a package.
+ */
+fun OrtDependency.isProjectDependency() = localPath != null

plugins/package-managers/gradle/src/main/kotlin/GradleDependencyHandler.kt

@@ -34,6 +34,8 @@ import org.ossreviewtoolkit.model.PackageLinkage
 import org.ossreviewtoolkit.model.Severity
 import org.ossreviewtoolkit.model.createAndLogIssue
 import org.ossreviewtoolkit.model.utils.DependencyHandler
+import org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel.dependencyType
+import org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel.isProjectDependency
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.utils.MavenSupport
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.utils.identifier
 import org.ossreviewtoolkit.utils.common.collectMessages
@@ -117,21 +119,4 @@ internal class GradleDependencyHandler(
             }
         }
     }
-
-    /**
-     * Determine the type of this dependency. This manager implementation uses Maven to resolve packages, so
-     * the type of dependencies to packages is typically _Maven_ unless no pom is available. Only for module
-     * dependencies, the type of this manager is used.
-     */
-    private fun OrtDependency.dependencyType(): String =
-        if (isProjectDependency()) {
-            managerName
-        } else {
-            pomFile?.let { "Maven" } ?: "Unknown"
-        }
 }
-
-/**
- * Return a flag whether this dependency references another project in the current build.
- */
-private fun OrtDependency.isProjectDependency() = localPath != null

plugins/package-managers/gradle/src/test/kotlin/GradleDependencyHandlerTest.kt

@@ -57,6 +57,7 @@ import org.ossreviewtoolkit.model.Scope
 import org.ossreviewtoolkit.model.Severity
 import org.ossreviewtoolkit.model.VcsInfo
 import org.ossreviewtoolkit.model.utils.DependencyGraphBuilder
+import org.ossreviewtoolkit.plugins.packagemanagers.gradlemodel.dependencyType
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.utils.MavenSupport
 
 /**
@@ -131,7 +132,7 @@ class GradleDependencyHandlerTest : WordSpec({
 
             val scopes = graph.createScopes()
 
-            scopeDependencies(scopes, scope).single { it.id.type == NAME }
+            scopeDependencies(scopes, scope).single { it.id.type == "Gradle" }
         }
 
         "collect information about packages" {
@@ -312,23 +313,20 @@ class GradleDependencyHandlerTest : WordSpec({
             val issues = mutableListOf<Issue>()
 
             every { maven.parsePackage(any(), any(), useReposFromDependencies = false) } throws exception
-            val handler = GradleDependencyHandler(NAME, maven)
+            val handler = GradleDependencyHandler("Gradle", maven)
 
             handler.createPackage(dep, issues) should beNull()
 
             issues should haveSize(1)
             with(issues.first()) {
-                source shouldBe NAME
+                source shouldBe "Gradle"
                 severity shouldBe Severity.ERROR
                 message should contain("${dep.groupId}:${dep.artifactId}:${dep.version}")
             }
         }
     }
 })
 
-/** The name of the package manager. */
-private const val NAME = "GradleTest"
-
 /** Remote repositories used by the test. */
 private val remoteRepositories = listOf(mockk<RemoteRepository>())
 
@@ -361,7 +359,7 @@ private fun createDependency(
  * this class.
  */
 private fun createGraphBuilder(): DependencyGraphBuilder<OrtDependency> {
-    val dependencyHandler = GradleDependencyHandler(NAME, createMavenSupport())
+    val dependencyHandler = GradleDependencyHandler("Gradle", createMavenSupport())
     dependencyHandler.repositories = remoteRepositories
     return DependencyGraphBuilder(dependencyHandler)
 }
@@ -389,20 +387,10 @@ private fun createMavenSupport(): MavenSupport {
     return maven
 }
 
-/**
- * Determine the type of the [Identifier] for this dependency.
- */
-private fun OrtDependency.type(): String =
-    if (localPath != null) {
-        NAME
-    } else {
-        "Maven"
-    }
-
 /**
  * Returns an [Identifier] for this [OrtDependency].
  */
-private fun OrtDependency.toId() = Identifier(type(), groupId, artifactId, version)
+private fun OrtDependency.toId() = Identifier(dependencyType(), groupId, artifactId, version)
 
 /**
  * Return the package references from the given [scopes] associated with the scope with the given [scopeName].