Add support for locator.properties

pom.xml

@@ -97,6 +97,12 @@
             <version>3.1.1</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.webjars.bower</groupId>
+            <artifactId>js-base64</artifactId>
+            <version>2.3.2</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
     <build>

src/main/java/org/webjars/WebJarVersionLocator.java

@@ -5,6 +5,9 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.net.URL;
+import java.util.Enumeration;
+import java.util.Map;
 import java.util.Optional;
 import java.util.Properties;
 import java.util.concurrent.ConcurrentHashMap;
@@ -25,17 +28,22 @@ public class WebJarVersionLocator {
     private static final String NPM = "org.webjars.npm/";
     private static final String PLAIN = "org.webjars/";
     private static final String POM_PROPERTIES = "/pom.properties";
+    private static final String LOCATOR_PROPERTIES = "/locator.properties";
+
+    private static final String CACHE_KEY_PREFIX = "version-";
 
     private static final ClassLoader LOADER = WebJarVersionLocator.class.getClassLoader();
 
     private final WebJarCache cache;
 
     public WebJarVersionLocator() {
         this.cache = new WebJarCacheDefault(new ConcurrentHashMap<>());
+        readLocatorProperties();
     }
 
     WebJarVersionLocator(WebJarCache cache) {
         this.cache = cache;
+        readLocatorProperties();
     }
 
     /**
@@ -83,7 +91,7 @@ public String path(final String webJarName, final String exactPath) {
      */
     @Nullable
     public String version(final String webJarName) {
-        final String cacheKey = "version-" + webJarName;
+        final String cacheKey = CACHE_KEY_PREFIX + webJarName;
         final Optional<String> optionalVersion = cache.computeIfAbsent(cacheKey, (key) -> {
             InputStream resource = LOADER.getResourceAsStream(PROPERTIES_ROOT + NPM + webJarName + POM_PROPERTIES);
             if (resource == null) {
@@ -126,6 +134,37 @@ public String version(final String webJarName) {
         return optionalVersion.orElse(null);
     }
 
+    private void readLocatorProperties() {
+        try {
+            Enumeration<URL> resources =
+                LOADER.getResources(WEBJARS_PATH_PREFIX + LOCATOR_PROPERTIES);
+            while (resources.hasMoreElements()) {
+                URL resourceUrl = resources.nextElement();
+                try (InputStream resource = resourceUrl.openStream()) {
+                    Properties properties = new Properties();
+                    properties.load(resource);
+                    for (Map.Entry<Object, Object> entry : properties.entrySet()) {
+                        String webJarName = entry.getKey().toString();
+                        if (!webJarName.endsWith(".version")) {
+                            // ".version" suffix is required
+                            continue;
+                        }
+
+                        webJarName = webJarName.substring(0, webJarName.lastIndexOf(".version"));
+
+                        String version = entry.getValue().toString();
+                        if (hasResourcePath(webJarName, version)) {
+                            // Only add configured versions if their path exists
+                            cache.computeIfAbsent(CACHE_KEY_PREFIX + webJarName, x -> Optional.of(version));
+                        }
+                    }
+                }
+            }
+        } catch (IOException e) {
+            throw new RuntimeException("unable to load locator properties", e);
+        }
+    }
+
     private boolean hasResourcePath(final String webJarName, final String path) {
         return LOADER.getResource(WEBJARS_PATH_PREFIX + "/" + webJarName + "/" + path) != null;
     }

src/test/java/org/webjars/WebJarVersionLocatorTest.java

@@ -8,6 +8,7 @@
 
 import java.util.Optional;
 import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
 import java.util.function.Function;
 
@@ -23,6 +24,21 @@ void should_get_a_webjar_version() {
         assertEquals("3.1.1", new WebJarVersionLocator().version("bootswatch-yeti"));
     }
 
+    @Test
+    void should_find_good_custom_webjar_version() {
+        assertEquals("3.2.1", new WebJarVersionLocator().version("goodwebjar"));
+    }
+
+    @Test
+    void should_not_find_bad_custom_webjar_version() {
+        assertNull(new WebJarVersionLocator().version("badwebjar"));
+    }
+
+    @Test
+    void should_find_bower_webjar_version() {
+        assertEquals("2.3.2", new WebJarVersionLocator().version("js-base64"));
+    }
+
     @Test
     void webjar_version_doesnt_match_path() {
         assertEquals("3.1.1", new WebJarVersionLocator().version("bootstrap"));
@@ -45,6 +61,7 @@ void full_path_exists_version_supplied() {
 
     @Test
     void cache_is_populated_on_lookup() {
+        AtomicBoolean shouldInspect = new AtomicBoolean(false);
         AtomicInteger numLookups = new AtomicInteger(0);
 
         @NullMarked
@@ -54,14 +71,18 @@ class InspectableCache implements WebJarCache {
             @Override
             public Optional<String> computeIfAbsent(String key, Function<String, Optional<String>> function) {
                 Function<String, Optional<String>> inspectableFunction = function.andThen((value) -> {
-                    numLookups.incrementAndGet();
+                    if(shouldInspect.get()) {
+                        numLookups.incrementAndGet();
+                    }
                     return value;
                 });
                 return cache.computeIfAbsent(key, inspectableFunction);
             }
         }
 
         final WebJarVersionLocator webJarVersionLocator = new WebJarVersionLocator(new InspectableCache());
+        // enable inspection after webJarVersionLocator has been constructed, to ignore lookups caused by loading locator.properties
+        shouldInspect.set(true);
 
         assertEquals("3.1.1", webJarVersionLocator.version("bootstrap"));
         assertEquals(1, numLookups.get());

src/test/resources/META-INF/resources/webjars/goodwebjar/3.2.1/goodwebjar.js

@@ -0,0 +1 @@
+// Awesome WebJar content

src/test/resources/META-INF/resources/webjars/locator.properties

@@ -0,0 +1,8 @@
+# WebJar that can be found on classpath
+goodwebjar.version=3.2.1
+
+# WebJar that is not present in classpath
+badwebjar.version=1.2.3
+
+# Bower Webjar from dependencies
+js-base64.version=2.3.2