[Core] Support nested jar file systems (#2830)

Spring Boot 3.2 changed the URL format of their nested jars[1] to be
more compliant with JDK expectations. They now represented nested jars
as their own `nested` scheme rather than the `file` scheme. This allows
these URLs to be used seamlessly with `FileSystems.newFileSystem`.

Unfortunately the workarounds for Spring Boot 3.1 did not account for
this.

Additionally, our jar uri parsing assumed naively that there would only
be a single `!/` in a regular jar uri. However, jar uris are
recursively defined as[2]:

```
jar:<url>!/[<entry>]
```

And while this should allow Cucumber to discover resources in nested
jars as well it does seem that Spring Boot 3.2 still has some issues[3].

Closes: #2828

1. https://github.com/spring-projects/spring-boot/wiki/Spring-Boot-3.2-Release-Notes
2. https://www.iana.org/assignments/uri-schemes/prov/jar
3. spring-projects/spring-boot#38595

Author: mpkorstanje

CHANGELOG.md

@@ -15,6 +15,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 - [Guice] Inject static fields prior to before all hooks ([#2803](https://github.com/cucumber/cucumber-jvm/pull/2803) M.P. Korstanje)
 
+### Added
+- [Core] Support nested jar file systems (i.e. Spring Boot 3.2) ([#2830](https://github.com/cucumber/cucumber-jvm/pull/2830) M.P. Korstanje)
+
 ## [7.14.0] - 2023-09-09
 ### Changed
 - [Core] Update dependency io.cucumber:html-formatter to v20.4.0

cucumber-core/src/main/java/io/cucumber/core/resource/ClasspathSupport.java

@@ -167,7 +167,8 @@ static String nestedJarEntriesExplanation(URI uri) {
                 "This typically happens when trying to run Cucumber inside a Spring Boot Executable Jar.\n" +
                 "Cucumber currently doesn't support classpath scanning in nested jars.\n" +
                 "\n" +
-                "You can avoid this error by unpacking your application before executing.\n" +
+                "You can avoid this error by unpacking your application before executing or upgrading to Spring Boot 3.2 or higher.\n"
+                +
                 "\n" +
                 "Alternatively you can restrict which packages cucumber scans configuring the glue path such that " +
                 "Cucumber only scans un-nested jars.\n" +

cucumber-core/src/main/java/io/cucumber/core/resource/JarUriFileSystemService.java

@@ -22,7 +22,7 @@ class JarUriFileSystemService {
     private static final String JAR_URI_SCHEME = "jar";
     private static final String JAR_URI_SCHEME_PREFIX = JAR_URI_SCHEME + ":";
     private static final String JAR_FILE_SUFFIX = ".jar";
-    private static final String JAR_URI_SEPARATOR = "!";
+    private static final String JAR_URI_SEPARATOR = "!/";
 
     private static final Map<URI, FileSystem> openFiles = new HashMap<>();
     private static final Map<URI, AtomicInteger> referenceCount = new HashMap<>();
@@ -67,13 +67,14 @@ private static boolean hasFileUriSchemeWithJarExtension(URI uri) {
     }
 
     static CloseablePath open(URI uri) throws URISyntaxException, IOException {
-        if (hasJarUriScheme(uri)) {
-            return handleJarUriScheme(uri);
-        }
+        assert supports(uri);
         if (hasFileUriSchemeWithJarExtension(uri)) {
             return handleFileUriSchemeWithJarExtension(uri);
         }
-        throw new IllegalArgumentException("Unsupported uri " + uri.toString());
+        if (isSpringBoot31OrLower(uri)) {
+            return handleSpringBoot31JarUri(uri);
+        }
+        return handleJarUriScheme(uri);
     }
 
     private static CloseablePath handleFileUriSchemeWithJarExtension(URI uri) throws IOException, URISyntaxException {
@@ -82,22 +83,44 @@ private static CloseablePath handleFileUriSchemeWithJarExtension(URI uri) throws
     }
 
     private static CloseablePath handleJarUriScheme(URI uri) throws IOException, URISyntaxException {
-        String[] parts = uri.toString().split(JAR_URI_SEPARATOR);
-        // Regular jar schemes
-        if (parts.length <= 2) {
-            String jarUri = parts[0];
-            String jarPath = parts.length == 2 ? parts[1] : "/";
-            return open(new URI(jarUri), fileSystem -> fileSystem.getPath(jarPath));
+        // Regular Jar Uris
+        // Format: jar:<url>!/[<entry>]
+        String uriString = uri.toString();
+        int lastJarUriSeparator = uriString.lastIndexOf(JAR_URI_SEPARATOR);
+        if (lastJarUriSeparator < 0) {
+            throw new IllegalArgumentException(String.format("jar uri '%s' must contain '%s'", uri, JAR_URI_SEPARATOR));
         }
+        String url = uriString.substring(0, lastJarUriSeparator);
+        String entry = uriString.substring(lastJarUriSeparator + 1);
+        return open(new URI(url), fileSystem -> fileSystem.getPath(entry));
+    }
 
-        // Spring boot jar scheme
+    private static boolean isSpringBoot31OrLower(URI uri) {
+        // Starting Spring Boot 3.2 the nested scheme is used. This works with
+        // regular jar file handling and doesn't need a workaround.
+        // Example 3.2:
+        // jar:nested:/dir/myjar.jar/!/BOOT-INF/lib/nested.jar!/com/example/MyClass.class
+        // Example 3.1:
+        // jar:file:/dir/myjar.jar/!/BOOT-INF/lib/nested.jar!/com/example/MyClass.class
+        String schemeSpecificPart = uri.getSchemeSpecificPart();
+        return schemeSpecificPart.startsWith("file:") && schemeSpecificPart.contains("!/BOOT-INF");
+    }
+
+    private static CloseablePath handleSpringBoot31JarUri(URI uri) throws IOException, URISyntaxException {
+        // Spring boot 3.1 jar scheme
+        // Examples:
+        // jar:file:/home/user/application.jar!/BOOT-INF/lib/dependency.jar!/com/example/dependency/resource.txt
+        // jar:file:/home/user/application.jar!/BOOT-INF/classes!/com/example/package/resource.txt
+        String[] parts = uri.toString().split("!");
         String jarUri = parts[0];
         String jarEntry = parts[1];
         String subEntry = parts[2];
         if (jarEntry.endsWith(JAR_FILE_SUFFIX)) {
             throw new CucumberException(nestedJarEntriesExplanation(uri));
         }
+        // We're looking directly at the files in the jar, so we construct the
+        // file path by concatenating the jarEntry and subEntry without the jar
+        // uri separator.
         return open(new URI(jarUri), fileSystem -> fileSystem.getPath(jarEntry + subEntry));
     }
-
 }

cucumber-core/src/test/java/io/cucumber/core/resource/ResourceScannerTest.java

@@ -159,6 +159,29 @@ void scanForResourcesJarUri() {
         assertThat(resources, contains(resourceUri));
     }
 
+    @Test
+    void scanForResourcesJarUriMalformed() {
+        URI jarFileUri = new File("src/test/resources/io/cucumber/core/resource/test/jar-resource.jar").toURI();
+        URI resourceUri = URI
+                .create("jar:file://" + jarFileUri.getSchemeSpecificPart() + "/com/example/package-jar-resource.txt");
+        IllegalArgumentException exception = assertThrows(
+            IllegalArgumentException.class,
+            () -> resourceScanner.scanForResourcesUri(resourceUri));
+        assertThat(exception.getMessage(),
+            containsString("jar uri '" + resourceUri + "' must contain '!/'"));
+    }
+
+    @Test
+    void scanForResourcesJarUriMissingEntry() {
+        URI jarFileUri = new File("src/test/resources/io/cucumber/core/resource/test/jar-resource.jar").toURI();
+        URI resourceUri = URI.create("jar:file://" + jarFileUri.getSchemeSpecificPart() + "");
+        IllegalArgumentException exception = assertThrows(
+            IllegalArgumentException.class,
+            () -> resourceScanner.scanForResourcesUri(resourceUri));
+        assertThat(exception.getMessage(),
+            containsString("jar uri '" + resourceUri + "' must contain '!/'"));
+    }
+
     @Test
     void scanForResourcesNestedJarUri() {
         URI jarFileUri = new File("src/test/resources/io/cucumber/core/resource/test/spring-resource.jar").toURI();