issues/133: part 3 - introduction of ClassFileSelector (#192)

issues/133: part 3 - introduction of ClassFileSelector

skippy-core/src/main/java/io/skippy/core/ClassFileSelector.java

@@ -0,0 +1,136 @@
+/*
+ * Copyright 2023-2024 the original author or authors.
+ *
+ * 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.
+ */
+
+package io.skippy.core;
+
+import java.util.List;
+
+/**
+ * Strategy to select {@link ClassFile}s from a {@link ClassFileContainer} based on
+ *
+ * <ul>
+ *     <li>class name and </li>
+ *     <li>class path.</li>
+ * </ul>
+ *
+ * Why is this needed? The same class name can occur multiple times within a project:
+ *
+ * <pre>
+ *     src/main/java/com.example.Foo
+ *     src/test/java/com.example.Foo
+ * </pre>
+ *
+ * The above example will result in multiple entries for the same class name in test-impact-analysis.java:
+ *
+ * <pre>
+ * {
+ *     "classes": {
+ *         "1": {
+ *             "name": "com.example.Foo",
+ *             "path": "com/example/Foo.class",
+ *             "outputFolder": "build/classes/java/integrationTest",
+ *             ...
+ *         }
+ *         "1": {
+ *             "name": "com.example.Foo",
+ *             "path": "com/example/Foo.class",
+ *             "outputFolder": "build/classes/java/test",
+ *             ...
+ *         }
+ *     ]
+ * }
+ * </pre>
+ *
+ * A {@link ClassFileSelector} can try to map a class name to a single {@link ClassFile} by taking
+ * the class path into account.
+ *
+ * <br /><br />
+ *
+ * Let's consider the classpath to be as follows:
+ *
+ * <pre>
+ * build/classes/java/test
+ * build/classes/java/main
+ * build/resources/main
+ * </pre>
+ *
+ * In the above classpath, com.example.Foo can be mapped to
+ *
+ * <pre>
+ * {
+ *      "name": "com.example.Foo",
+ *      "path": "com/example/Foo.class",
+ *      "outputFolder": "build/classes/java/test",
+ *      ...
+ * }
+ * </pre>
+ *
+ * Now, let's consider the following classpath:
+ *
+ * <pre>
+ * build/classes/java/integrationTest
+ * build/classes/java/main
+ * build/resources/main
+ * </pre>
+ *
+ * In this example, com.example.Foo can be mapped to
+ *
+ * <pre>
+ * {
+ *      "name": "com.example.Foo",
+ *      "path": "com/example/Foo.class",
+ *      "outputFolder": "build/classes/java/integrationTest",
+ *      ...
+ * }
+ * </pre>
+ *
+ * If no exact match is possible, then multiple {@link ClassFile}s can be returned. This is safe, but it might result in
+ * unnecessary {@link Prediction#EXECUTE} predictions.
+ *
+ * <br /><br />
+ *
+ * Custom implementations must have a public no-args constructor.
+ * They can be registered using Skippy's build plugins.
+ *
+ * <br /><br />
+ *
+ * Gradle example:
+ * <pre>
+ * skippy {
+ *     ...
+ *     classFileSelector = 'com.example.CustomClassFileSelector'
+ * }
+ * </pre>
+ *
+ * @author Florian McKee
+ */
+public interface ClassFileSelector {
+
+    /**
+     * Select {@link ClassFile}s from the {@code classFileContainer} based on
+     *
+     * <ul>
+     *     <li>{@code className} and </li>
+     *     <li>{@code classPath}.</li>
+     * </ul>
+     * @param className a class name (e.g., com.example.Foo)
+     * @param classFileContainer a {@link ClassFileContainer}
+     * @param classPath a list of folders within the project's output folders that contribute to the classpath (e.g. build/classes/java/main).
+     *
+     * @return all matching {@link ClassFile}s
+     */
+    List<ClassFile> select(String className, ClassFileContainer classFileContainer, List<String> classPath);
+}

skippy-core/src/main/java/io/skippy/core/DefaultClassFileSelector.java

@@ -0,0 +1,51 @@
+package io.skippy.core;
+
+import java.nio.file.Path;
+import java.util.List;
+
+import static java.util.Collections.emptyList;
+
+/**
+ * Default {@link ClassFileSelector} implementation.
+ *
+ * @author Florian McKee
+ */
+public final class DefaultClassFileSelector implements ClassFileSelector {
+
+    /**
+     * Comment to make the JavaDoc task happy.
+     */
+    public DefaultClassFileSelector() {
+    }
+
+    @Override
+    public List<ClassFile> select(String className, ClassFileContainer classFileContainer, List<String> classPath) {
+
+        // try to match by class name only
+        var classFiles = classFileContainer.getIdsByClassName(className).stream().map(classFileContainer::getById).toList();
+
+        // no match? return nothing
+        if (classFiles.size() == 0) {
+            return emptyList();
+        }
+
+        // exactly one match? return the match
+        if (classFiles.size() == 1) {
+            return List.of(classFiles.get(0));
+        }
+
+        // iterate through the classpath folders
+        for (var classPathEntry : classPath) {
+
+            // check for a match for the given folder
+            var matchingClassFiles = classFiles.stream().filter(classFile -> classFile.getOutputFolder().equals(Path.of(classPathEntry))).toList();
+
+            if (matchingClassFiles.size() == 1) {
+                return List.of(matchingClassFiles.get(0));
+            }
+        }
+
+        // no exact match found: return all candidates (this is safe, but it will result in unnecessary execute predictions)
+        return classFiles;
+    }
+}

skippy-core/src/main/java/io/skippy/core/DefaultPredictionModifier.java

@@ -19,7 +19,7 @@
 import java.util.Optional;
 
 /**
- * {@link PredictionModifier} that defaults to {@link Prediction#EXECUTE} if a test (or one of it's superclasses or
+ * {@link PredictionModifier} that defaults to {@link Prediction#EXECUTE} if a test (or one of its superclasses or
  * interfaces it implements is annotated with @{@link AlwaysRun}.
  *
  * @author Florian McKee
@@ -30,7 +30,7 @@ public DefaultPredictionModifier() {
     }
 
     @Override
-    public PredictionWithReason passThruOrModify(Class<?> test, ParametersFromBuildPlugin parametersFromBuildPlugin, PredictionWithReason prediction) {
+    public PredictionWithReason passThruOrModify(Class<?> test, PredictionWithReason prediction) {
         if (isAnnotatedWithAlwaysRun(test)) {
             return new PredictionWithReason(
                 Prediction.ALWAYS_EXECUTE,

skippy-core/src/main/java/io/skippy/core/HashUtil.java

@@ -48,6 +48,16 @@ static String hashWith32Digits(byte[] data) {
         return fullHash(data);
     }
 
+    /**
+     * Generates an 8-character hexadecimal hash of the input.
+     *
+     * @param data the input
+     * @return ab 8-character hexadecimal hash of the input
+     */
+    static String hashWith8Digits(byte[] data) {
+        return fullHash(data).substring(24, 32);
+    }
+
     /**
      * Generates a 8-digit hexadecimal hash for the {@code classfile} that is agnostic of debug information.
      *
@@ -65,7 +75,7 @@ static String hashWith32Digits(byte[] data) {
      * @return a 8-digit hexadecimal  hash of the {@code classfile} that is agnostic of debug information
      */
     static String debugAgnosticHash(Path classFile) {
-        return fullHash(getBytecodeWithoutDebugInformation(classFile)).substring(24, 32);
+        return hashWith8Digits(getBytecodeWithoutDebugInformation(classFile));
     }
 
     private static String fullHash(byte[] data) {

skippy-core/src/main/java/io/skippy/core/PredictionModifier.java

@@ -26,9 +26,11 @@
  *     <li>etc.</li>
  * </ul>
  *
+ * Custom implementations must have a public no-args constructor.
+ * They can be registered using Skippy's build plugins.
+ *
  * <br /><br />
- * Custom implementations must be registered using Skippy's build plugins.
- * <br /><br />
+ *
  * Gradle example:
  * <pre>
  * skippy {
@@ -45,10 +47,9 @@ public interface PredictionModifier {
      * Returns a modified or unmodified prediction made by Skippy.
      *
      * @param test a class object representing a test
-     * @param parametersFromBuildPlugin parameters that have been passed from Skippy's build plugin
      * @param prediction the prediction made by Skippy.
      * @return the modified or unmodified prediction
      */
-    PredictionWithReason passThruOrModify(Class<?> test, ParametersFromBuildPlugin parametersFromBuildPlugin, PredictionWithReason prediction);
+    PredictionWithReason passThruOrModify(Class<?> test, PredictionWithReason prediction);
 
 }