Ignore JARs without a Smithy manifest

This commit logs when a JAR is encountered with a missing manifest
instead of throwing, allowing for libraries that bring in Smithy
models to have dependencies on non-Smithy packages.

Author: kstich

.changes/next-release/feature-6dc2e6dcfbad136a8cffecc102b0f02214cd9e46.json

@@ -0,0 +1,5 @@
+{
+  "type": "feature",
+  "description": "Ignore JARs without a Smithy manifest to allow Smithy model packages to have non-Smithy dependencies",
+  "pull_requests": []
+}

smithy-model/src/main/java/software/amazon/smithy/model/loader/ModelLoader.java

@@ -4,10 +4,12 @@
  */
 package software.amazon.smithy.model.loader;
 
+import java.io.FileNotFoundException;
 import java.io.IOException;
 import java.io.InputStream;
 import java.net.URL;
 import java.net.URLConnection;
+import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Function;
@@ -118,7 +120,18 @@ private static void loadJar(
         URL manifestUrl = ModelDiscovery.createSmithyJarManifestUrl(filename);
         LOGGER.fine(() -> "Loading Smithy model imports from JAR: " + manifestUrl);
 
-        for (URL model : ModelDiscovery.findModels(manifestUrl)) {
+        List<URL> models;
+        try {
+            models = ModelDiscovery.findModels(manifestUrl);
+        } catch (ModelManifestException e) {
+            if (e.getCause() instanceof FileNotFoundException) {
+                LOGGER.info(() -> "Ignoring JAR without Smithy manifest: " + filename);
+                return;
+            }
+            throw e;
+        }
+
+        for (URL model : models) {
             try {
                 URLConnection connection = model.openConnection();
 

smithy-model/src/test/java/software/amazon/smithy/model/loader/ModelAssemblerTest.java

@@ -1347,6 +1347,16 @@ public void failsOnInvalidJarJsonFile() throws URISyntaxException, IOException {
         assertThat(e.getMessage(), containsString("Invalid file referenced by Smithy JAR manifest"));
     }
 
+    @Test
+    public void ignoresJarWithoutSmithyManifest() throws URISyntaxException, IOException {
+        Path jar = JarUtils.createJarFromDir(
+                Paths.get(getClass().getResource("assembler-no-manifest-jar").toURI()));
+
+        ValidatedResult<Model> result = Model.assembler().addImport(jar).assemble();
+
+        assertFalse(result.isBroken());
+    }
+
     @Test
     public void doesNotThrowOnInvalidSuppression() {
         ObjectNode node = Node.objectNode()

smithy-model/src/test/resources/software/amazon/smithy/model/loader/assembler-no-manifest-jar/META-INF/MANIFEST.MF

@@ -0,0 +1 @@
+Manifest-Version: 1.0