Do not fail if a classpath entry is missing

The resource detection mechanism should be lenient with regards to
entries which might be missing from the classpath. For example, in
case of an empty `src/test/resources` directory, the Gradle test
process resources task would not create a `build/test/resources`
directory, which causes a failure.

Fixes #175

Author: melix

common/utils/build.gradle.kts

@@ -52,6 +52,12 @@ maven {
 
 dependencies {
     implementation(libs.jackson.databind)
+    implementation(platform(libs.test.junit.bom))
+    implementation(libs.test.junit.jupiter.core)
+}
+
+tasks.withType<Test>().configureEach {
+    useJUnitPlatform()
 }
 
 val generateVersionInfo = tasks.register("generateVersionInfo", org.graalvm.build.GenerateVersionClass::class.java) {

common/utils/src/main/java/org/graalvm/buildtools/model/resources/ClassPathDirectoryAnalyzer.java

@@ -64,9 +64,14 @@ class ClassPathDirectoryAnalyzer extends ClassPathEntryAnalyzer {
     }
 
     protected List<String> initialize() throws IOException {
-        DirectoryVisitor visitor = new DirectoryVisitor();
-        Files.walkFileTree(root, visitor);
-        return visitor.hasNativeImageResourceFile && !ignoreExistingResourcesConfig ? Collections.emptyList() : visitor.resources;
+        if (Files.exists(root)) {
+            DirectoryVisitor visitor = new DirectoryVisitor();
+            Files.walkFileTree(root, visitor);
+            return visitor.hasNativeImageResourceFile && !ignoreExistingResourcesConfig ? Collections.emptyList() : visitor.resources;
+        }
+        else {
+            return Collections.emptyList();
+        }
     }
 
     private class DirectoryVisitor extends SimpleFileVisitor<Path> {

common/utils/src/main/java/org/graalvm/buildtools/model/resources/JarAnalyzer.java

@@ -63,22 +63,26 @@ class JarAnalyzer extends ClassPathEntryAnalyzer {
     }
 
     protected List<String> initialize() throws IOException {
-        List<String> resources = new ArrayList<>();
-        boolean hasNativeImageResourceFile = false;
-        try (JarInputStream zin = new JarInputStream(new FileInputStream(jarFile))) {
-            ZipEntry entry;
-            while ((entry = zin.getNextEntry()) != null) {
-                hasNativeImageResourceFile = FileUtils.normalizePathSeparators(entry.getName()).startsWith(Helper.META_INF_NATIVE_IMAGE + "/")
-                    && entry.getName().endsWith("resource-config.json");
+        if (jarFile.exists()) {
+            List<String> resources = new ArrayList<>();
+            boolean hasNativeImageResourceFile = false;
+            try (JarInputStream zin = new JarInputStream(new FileInputStream(jarFile))) {
+                ZipEntry entry;
+                while ((entry = zin.getNextEntry()) != null) {
+                    hasNativeImageResourceFile = FileUtils.normalizePathSeparators(entry.getName()).startsWith(Helper.META_INF_NATIVE_IMAGE + "/")
+                            && entry.getName().endsWith("resource-config.json");
 
-                if (hasNativeImageResourceFile && !ignoreExistingResourcesConfig) {
-                    break;
-                }
-                if (!entry.isDirectory()) {
-                    maybeAddResource(entry.getName(), resources);
+                    if (hasNativeImageResourceFile && !ignoreExistingResourcesConfig) {
+                        break;
+                    }
+                    if (!entry.isDirectory()) {
+                        maybeAddResource(entry.getName(), resources);
+                    }
                 }
             }
+            return hasNativeImageResourceFile && !ignoreExistingResourcesConfig ? Collections.emptyList() : resources;
+        } else {
+            return Collections.emptyList();
         }
-        return hasNativeImageResourceFile && !ignoreExistingResourcesConfig ? Collections.emptyList() : resources;
     }
 }

common/utils/src/test/java/org/graalvm/buildtools/utils/ClassPathEntryAnalyzerTest.java

@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2020, 2021 Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * The Universal Permissive License (UPL), Version 1.0
+ *
+ * Subject to the condition set forth below, permission is hereby granted to any
+ * person obtaining a copy of this software, associated documentation and/or
+ * data (collectively the "Software"), free of charge and under any and all
+ * copyright rights in the Software, and any and all patent rights owned or
+ * freely licensable by each licensor hereunder covering either (i) the
+ * unmodified Software as contributed to or provided by such licensor, or (ii)
+ * the Larger Works (as defined below), to deal in both
+ *
+ * (a) the Software, and
+ *
+ * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+ * one is included with the Software each a "Larger Work" to which the Software
+ * is contributed by such licensors),
+ *
+ * without restriction, including without limitation the rights to copy, create
+ * derivative works of, display, perform, and distribute the Software and make,
+ * use, sell, offer for sale, import, export, have made, and have sold the
+ * Software and the Larger Work(s), and to sublicense the foregoing rights on
+ * either these or other terms.
+ *
+ * This license is subject to the following condition:
+ *
+ * The above copyright notice and either this complete permission notice or at a
+ * minimum a reference to the UPL must be included in all copies or substantial
+ * portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package org.graalvm.buildtools.utils;
+
+import org.graalvm.buildtools.model.resources.ClassPathEntryAnalyzer;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Collections;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ClassPathEntryAnalyzerTest {
+    @Test
+    @DisplayName("A non existent jar shouldn't cause an exception")
+    public void testShouldAllowNonExistentJar() throws IOException {
+        ClassPathEntryAnalyzer analyzer = ClassPathEntryAnalyzer.of(
+                new File("dummy.jar"),
+                s -> true,
+                false
+        );
+        assertEquals(Collections.emptyList(), analyzer.getResources());
+    }
+
+    @Test
+    @DisplayName("A non existent directory shouldn't cause an exception")
+    public void testShouldAllowNonExistentDir() throws IOException {
+        ClassPathEntryAnalyzer analyzer = ClassPathEntryAnalyzer.of(
+                new File("dummy-dir"),
+                s -> true,
+                false
+        );
+        assertEquals(Collections.emptyList(), analyzer.getResources());
+    }
+}