gazelle/kotln: Fix import resolution to use ancestor packages

gazelle/kotlin/imports.go

@@ -1,19 +1,65 @@
 package gazelle
 
 import (
+	"strings"
+
 	"github.com/bazelbuild/bazel-gazelle/resolve"
 	godsutils "github.com/emirpasic/gods/utils"
 )
 
-// TODO: drop? still used?
+// ImportStatement corresponds to a single Kotlin import. Only the package
+// information is retained in this representation of the import.
 type ImportStatement struct {
 	resolve.ImportSpec
 
 	// The path of the file containing the import
 	SourcePath string
 }
 
+// packageFullyQualifiedName returns a [javaFullyQualifiedName] of package of the import.
+//
+// for "import foo.Bar as X", returns "foo"
+// for "import foo.* as X", returns "foo"
+func (is *ImportStatement) packageFullyQualifiedName() *javaFullyQualifiedName {
+	return &javaFullyQualifiedName{strings.Split(is.Imp, ".")}
+}
+
 // importStatementComparator compares modules by name.
 func importStatementComparator(a, b interface{}) int {
 	return godsutils.StringComparator(a.(ImportStatement).Imp, b.(ImportStatement).Imp)
 }
+
+// javaFullyQualifiedName represents a fully-qualified name in Java, which is
+// a dot-delimited list of [identifiers].
+//
+// [identifiers]: https://docs.oracle.com/javase/specs/jls/se23/html/jls-3.html#jls-Identifier
+type javaFullyQualifiedName struct {
+	// Each component of the path is an identifier.
+	// https://kotlinlang.org/spec/syntax-and-grammar.html#grammar-rule-importList.
+	//
+	// A Java identifier that should mostly correspond to [3.8. Identifiers] from
+	// the Java spec.
+	//
+	// [3.8. Identifiers]: https://docs.oracle.com/javase/specs/jls/se23/html/jls-3.html#jls-JavaLetter
+	//
+	// [L letter class]: https://stackoverflow.com/questions/5969440/what-is-the-l-unicode-category
+	parts []string
+}
+
+// String  returns the dot-delimited java package name as it would appear in
+// source code.
+func (jpn *javaFullyQualifiedName) String() string {
+	return strings.Join(jpn.parts, ".")
+}
+
+// Parent returns the parent package.
+func (jpn *javaFullyQualifiedName) Parent() *javaFullyQualifiedName {
+	if jpn == nil || len(jpn.parts) <= 1 {
+		return nil
+	}
+	return &javaFullyQualifiedName{jpn.parts[0 : len(jpn.parts)-1]}
+}
+
+func importAsFQN(is *ImportStatement) *javaFullyQualifiedName {
+	return &javaFullyQualifiedName{strings.Split(is.Imp, ".")}
+}

gazelle/kotlin/resolver.go

@@ -191,11 +191,20 @@ func (kt *kotlinLang) resolveImport(
 		if l, mavenError := (*mavenResolver).Resolve(jvm_import, cfg.ExcludedArtifacts(), cfg.MavenRepositoryName()); mavenError == nil {
 			return Resolution_Label, &l, nil
 		} else {
-			BazelLog.Debugf("Maven resolution error: %v", mavenError)
+			BazelLog.Debugf("Maven resolution failed: %v", mavenError)
 		}
 	}
 
-	return Resolution_NotFound, nil, nil
+	// The original import, like "x.y.z" might be a subpackage within a package that resolves,
+	// so try to resolve the original identifer, then try to resolve the parent
+	// identifier, etc.
+	importParent := impt.packageFullyQualifiedName().Parent()
+	if importParent == nil {
+		return Resolution_NotFound, nil, nil
+	}
+	parentImportSpec := impt
+	parentImportSpec.Imp = importParent.String()
+	return kt.resolveImport(c, ix, parentImportSpec, from)
 }
 
 // targetListFromResults returns a string with the human-readable list of

gazelle/kotlin/tests/deep_import/BUILD.in

@@ -0,0 +1 @@
+# TODO(gazelle:)java_maven_repository_name vendor_java

gazelle/kotlin/tests/deep_import/BUILD.out

@@ -0,0 +1 @@
+# TODO(gazelle:)java_maven_repository_name vendor_java

gazelle/kotlin/tests/deep_import/README.md

@@ -0,0 +1,8 @@
+Copied from
+[rules_jvm "maven" test](https://github.com/bazel-contrib/rules_jvm/tree/v0.17.0/java/gazelle/testdata/maven).
+
+Created by ~ following steps:
+
+1. Copy the rules_jvm "maven" test
+2. Rename .java to .kt
+3. Modify .kt files to Kotlin syntax with a minimal diff

gazelle/kotlin/tests/deep_import/WORKSPACE

@@ -0,0 +1,27 @@
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+
+http_archive(
+    name = "rules_jvm_external",
+    sha256 = "23fe83890a77ac1a3ee143e2306ec12da4a845285b14ea13cb0df1b1e23658fe",
+    strip_prefix = "rules_jvm_external-4.3",
+    urls = ["https://github.com/bazelbuild/rules_jvm_external/archive/refs/tags/4.3.tar.gz"],
+)
+
+load("@rules_jvm_external//:defs.bzl", "maven_install")
+
+maven_install(
+    artifacts = [
+        "junit:junit:4.13.1",
+        "com.google.guava:guava:30.0-jre",
+    ],
+    fetch_sources = True,
+    maven_install_json = "//:maven_install.json",
+    repositories = [
+        "http://uk.maven.org/maven2",
+        "https://jcenter.bintray.com/",
+    ],
+)
+
+load("@maven//:defs.bzl", "pinned_maven_install")
+
+pinned_maven_install()