[JUnit Platform] Support discovery selectors with FilePosition

There was no good way to discover and execute a single test when using a file
based test system like Cucumber. Recently JUnit added support for file position
in the `FileSelector` and `ClasspathResourceSelector`.

See: junit-team/junit5#2146

This implements a filter that prunes all scenarios that do not match the
`FilePosition` from the discovery selector. This feature itself is not new. It
was already implemented for the `UriSelector`.

Author: mpkorstanje

CHANGELOG.md

@@ -8,8 +8,10 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ## [Unreleased] (In Git)
 
 ### Added
+ * [JUnit Platform] Support discovery selectors with FilePosition ([2121](https://github.com/cucumber/cucumber-jvm/pull/2121) M.P. Korstanje) 
 
 ### Changed
+ * [JUnit Platform] Update dependency org.junit.platform:junit-platform-engine to v1.7.0
 
 ### Deprecated
 

junit-platform-engine/README.md

@@ -237,10 +237,17 @@ Supported `DiscoverySelector`s are:
 The only supported `DiscoveryFilter` is the `PackageNameFilter` and only when
 features are selected from the classpath.
 
+### Selecting individual scenarios, rules and examples 
+
+The `FileSelector` and `ClasspathResourceSelector` support the `FilePosition`.
+
+ * `DiscoverySelectors.selectClasspathResource("rule.feature", FilePosition.from(5))`
+ * `DiscoverySelectors.selectFile("rule.feature", FilePosition.from(5))`
+
 The `UriSelector` supports URI's with a `line` query parameter:
   - `classpath:/com/example/example.feature?line=20`
   - `file:/path/to/com/example/example.feature?line=20`
- 
+
 Any `TestDescriptor` that matches the line *and* its descendants will be
 included in the discovery result.
 

junit-platform-engine/src/main/java/io/cucumber/junit/platform/engine/FeatureResolver.java

@@ -23,7 +23,6 @@
 import org.junit.platform.engine.support.descriptor.FileSource;
 
 import java.net.URI;
-import java.nio.file.Path;
 import java.util.Optional;
 import java.util.UUID;
 import java.util.function.Predicate;
@@ -62,16 +61,20 @@ static FeatureResolver createFeatureResolver(
     }
 
     void resolveFile(FileSelector selector) {
-        resolvePath(selector.getPath());
-    }
+        Predicate<TestDescriptor> keepTestOnSelectedLine = selector.getPosition()
+                .map(filePosition -> filePosition.getLine())
+                .map(FeatureResolver::testDescriptorOnLine)
+                .orElse(testDescriptor -> true);
 
-    private void resolvePath(Path path) {
         featureScanner
-                .scanForResourcesPath(path)
+                .scanForResourcesPath(selector.getPath())
                 .stream()
                 .sorted(comparing(Feature::getUri))
                 .map(this::createFeatureDescriptor)
-                .forEach(engineDescriptor::mergeFeature);
+                .forEach(featureDescriptor -> {
+                    featureDescriptor.prune(keepTestOnSelectedLine);
+                    engineDescriptor.mergeFeature(featureDescriptor);
+                });
     }
 
     private FeatureDescriptor createFeatureDescriptor(Feature feature) {
@@ -137,7 +140,12 @@ private String getNameOrKeyWord(Node node) {
     }
 
     void resolveDirectory(DirectorySelector selector) {
-        resolvePath(selector.getPath());
+        featureScanner
+                .scanForResourcesPath(selector.getPath())
+                .stream()
+                .sorted(comparing(Feature::getUri))
+                .map(this::createFeatureDescriptor)
+                .forEach(engineDescriptor::mergeFeature);
     }
 
     void resolvePackageResource(PackageSelector selector) {
@@ -163,12 +171,21 @@ void resolveClass(ClassSelector classSelector) {
 
     void resolveClasspathResource(ClasspathResourceSelector selector) {
         String classpathResourceName = selector.getClasspathResourceName();
+
+        Predicate<TestDescriptor> keepTestOnSelectedLine = selector.getPosition()
+                .map(filePosition -> filePosition.getLine())
+                .map(FeatureResolver::testDescriptorOnLine)
+                .orElse(testDescriptor -> true);
+
         featureScanner
                 .scanForClasspathResource(classpathResourceName, packageFilter)
                 .stream()
                 .sorted(comparing(Feature::getUri))
                 .map(this::createFeatureDescriptor)
-                .forEach(engineDescriptor::mergeFeature);
+                .forEach(featureDescriptor -> {
+                    featureDescriptor.prune(keepTestOnSelectedLine);
+                    engineDescriptor.mergeFeature(featureDescriptor);
+                });
     }
 
     void resolveClasspathRoot(ClasspathRootSelector selector) {

junit-platform-engine/src/test/java/io/cucumber/junit/platform/engine/DiscoverySelectorResolverTest.java

@@ -11,6 +11,7 @@
 import org.junit.platform.engine.TestDescriptor;
 import org.junit.platform.engine.UniqueId;
 import org.junit.platform.engine.discovery.DiscoverySelectors;
+import org.junit.platform.engine.discovery.FilePosition;
 import org.junit.platform.engine.discovery.UniqueIdSelector;
 
 import java.io.File;
@@ -62,6 +63,28 @@ void resolveRequestWithClasspathResourceSelector() {
         assertEquals(1, testDescriptor.getChildren().size());
     }
 
+    @Test
+    void resolveRequestWithClasspathResourceSelectorAndFilePosition() {
+        DiscoverySelector resource = selectClasspathResource("io/cucumber/junit/platform/engine/rule.feature", FilePosition.from(5));
+        EngineDiscoveryRequest discoveryRequest = new SelectorRequest(resource);
+        resolver.resolveSelectors(discoveryRequest, testDescriptor);
+        assertEquals(1L, testDescriptor.getDescendants()
+                .stream()
+                .filter(TestDescriptor::isTest)
+                .count());
+    }
+
+    @Test
+    void resolveRequestWithClasspathResourceSelectorAndFilePositionOfContainer() {
+        DiscoverySelector resource = selectClasspathResource("io/cucumber/junit/platform/engine/rule.feature", FilePosition.from(3));
+        EngineDiscoveryRequest discoveryRequest = new SelectorRequest(resource);
+        resolver.resolveSelectors(discoveryRequest, testDescriptor);
+        assertEquals(2L, testDescriptor.getDescendants()
+                .stream()
+                .filter(TestDescriptor::isTest)
+                .count());
+    }
+
     @Test
     void resolveRequestWithMultipleClasspathResourceSelector() {
         DiscoverySelector resource1 = selectClasspathResource("io/cucumber/junit/platform/engine/single.feature");
@@ -155,6 +178,28 @@ void resolveRequestWithFileSelector() {
         assertEquals(1, testDescriptor.getChildren().size());
     }
 
+    @Test
+    void resolveRequestWithFileSelectorAndPosition() {
+        DiscoverySelector resource = selectFile("src/test/resources/io/cucumber/junit/platform/engine/rule.feature", FilePosition.from(5));
+        EngineDiscoveryRequest discoveryRequest = new SelectorRequest(resource);
+        resolver.resolveSelectors(discoveryRequest, testDescriptor);
+        assertEquals(1L, testDescriptor.getDescendants()
+                .stream()
+                .filter(TestDescriptor::isTest)
+                .count());
+    }
+
+    @Test
+    void resolveRequestWithFileSelectorAndPositionOfContainer() {
+        DiscoverySelector resource = selectFile("src/test/resources/io/cucumber/junit/platform/engine/rule.feature", FilePosition.from(3));
+        EngineDiscoveryRequest discoveryRequest = new SelectorRequest(resource);
+        resolver.resolveSelectors(discoveryRequest, testDescriptor);
+        assertEquals(2L, testDescriptor.getDescendants()
+                .stream()
+                .filter(TestDescriptor::isTest)
+                .count());
+    }
+
     @Test
     void resolveRequestWithDirectorySelector() {
         DiscoverySelector resource = selectDirectory("src/test/resources/io/cucumber/junit/platform/engine");