fix: compute longest common prefix for sibling packages in empty source roots

bundles/com.salesforce.bazel.eclipse.core/src/com/salesforce/bazel/eclipse/core/model/discovery/BaseProvisioningStrategy.java

@@ -1262,7 +1262,28 @@ private IPath findCommonParentPackagePrefix(Collection<IPath> detectedJavaPackag
             }
         }
 
-        return null;
+        // none of the detected packages is a prefix of all others (sibling packages case)
+        // compute the actual longest common prefix path
+        // e.g. for [com/foo/bar/dto, com/foo/bar/merge] this yields com/foo/bar
+        IPath commonPrefix = null;
+        for (IPath path : detectedJavaPackagesForSourceDirectory) {
+            if (commonPrefix == null) {
+                commonPrefix = path;
+            } else {
+                var minLen = Math.min(commonPrefix.segmentCount(), path.segmentCount());
+                var commonLen = 0;
+                for (var i = 0; i < minLen; i++) {
+                    if (commonPrefix.segment(i).equals(path.segment(i))) {
+                        commonLen = i + 1;
+                    } else {
+                        break;
+                    }
+                }
+                commonPrefix = commonPrefix.uptoSegment(commonLen);
+            }
+        }
+
+        return (commonPrefix == null) || commonPrefix.isEmpty() ? null : commonPrefix;
     }
 
     private IProject findProjectForLocation(IPath location) {

bundles/com.salesforce.bazel.eclipse.core/src/com/salesforce/bazel/eclipse/core/model/discovery/JavaAspectsClasspathInfo.java

@@ -358,6 +358,8 @@ public CompileAndRuntimeClasspath compute() throws CoreException {
                 var libraryArtifact = new LibraryArtifact(artifact, classJar, srcJars);
                 var targetKey = targetLabel != null ? TargetKey.forPlainTarget(targetLabel) : null;
                 library = new BlazeJarLibrary(libraryArtifact, targetKey);
+                // Register back to avoid repeated fallback for the same jar across multiple targets
+                aspectsInfo.registerFallbackLibrary(artifact.getRelativePath(), library);
             }
             var entry = resolveLibrary(library);
             if (entry != null) {
@@ -375,9 +377,14 @@ public CompileAndRuntimeClasspath compute() throws CoreException {
                     classpathBuilder.addCompileEntry(entry);
                 } else {
                     entry.getAccessRules().add(new AccessRule(PATTERN_EVERYTHING, IAccessRule.K_ACCESSIBLE));
+                    // Export EXPLICIT jdeps entries so downstream projects can resolve types
+                    // referenced in this project's public API. This addresses ECJ vs javac differences:
+                    // ECJ aggressively resolves all types in the API chain, while javac may not
+                    // record them in jdeps of downstream targets.
+                    entry.setExported(true);
                     classpathBuilder.addCompileEntry(entry);
                 }
-            } else if (LOG.isDebugEnabled()) {
+            } else {
                 LOG.warn("Unable to resolve compile jar: {}", jdepsDependency);
             }
         }

bundles/com.salesforce.bazel.eclipse.core/src/com/salesforce/bazel/eclipse/core/model/discovery/JavaAspectsInfo.java

@@ -261,6 +261,18 @@ private void addLibrary(BlazeJarLibrary library) {
         var classJar = libraryArtifact.getClassJar();
         if (classJar != null) {
             libraryByJdepsRootRelativePath.put(classJar.getRelativePath(), library);
+
+            // When there is no interfaceJar (e.g., libraries discovered from runtime classpath),
+            // also index under potential ijar/hjar paths so that jdeps lookups can find them.
+            // jdeps files typically reference ijar/hjar paths, not class jar paths.
+            if (interfaceJar == null) {
+                var classPath = classJar.getRelativePath();
+                if (classPath.endsWith(".jar")) {
+                    var base = classPath.substring(0, classPath.length() - ".jar".length());
+                    libraryByJdepsRootRelativePath.putIfAbsent(base + "-ijar.jar", library);
+                    libraryByJdepsRootRelativePath.putIfAbsent(base + "-hjar.jar", library);
+                }
+            }
         }
     }
 
@@ -276,6 +288,14 @@ public BlazeJarLibrary getLibraryByJdepsRootRelativePath(String relativePath) {
         return libraryByJdepsRootRelativePath.get(relativePath);
     }
 
+    /**
+     * Registers a fallback library discovered during jdeps resolution so that subsequent lookups for the same path
+     * don't need to repeat the fallback logic.
+     */
+    public void registerFallbackLibrary(String relativePath, BlazeJarLibrary library) {
+        libraryByJdepsRootRelativePath.putIfAbsent(relativePath, library);
+    }
+
     /**
      * Checks if a JAR file comes from an external Bazel repository.
      * <p>