Fix java_binary targets in test trees

Before they were generated with a dependency on a target which didn't
exist.

Instead, add the dependency on the -test-lib target of the
java_test_suite in their package, and mark them as testonly.

This is hopefully a pretty rare edge-case, but has been observed.

java/gazelle/generate.go

@@ -190,8 +190,22 @@ func (l javaLang) GenerateRules(args language.GenerateArgs) language.GenerateRes
 		l.generateJavaLibrary(args.File, args.Rel, filepath.Base(args.Rel), productionJavaFiles.SortedSlice(), allPackageNames, nonLocalProductionJavaImports, nonLocalJavaExports, false, javaLibraryKind, &res)
 	}
 
+	var testHelperJavaClasses *sorted_set.SortedSet[types.ClassName]
 	for _, m := range allMains.SortedSlice() {
-		l.generateJavaBinary(args.File, m, filepath.Base(args.Rel), &res)
+		// Lazily populate because java_binaries are pretty rare
+		if testHelperJavaClasses == nil {
+			testHelperJavaClasses = sorted_set.NewSortedSetFn[types.ClassName]([]types.ClassName{}, types.ClassNameLess)
+			for _, testHelperJavaFile := range testHelperJavaFiles.SortedSlice() {
+				testHelperJavaClasses.Add(*testHelperJavaFile.ClassName())
+			}
+		}
+		isTestOnly := false
+		libName := filepath.Base(args.Rel)
+		if testHelperJavaClasses.Contains(m) {
+			isTestOnly = true
+			libName += "-test-lib"
+		}
+		l.generateJavaBinary(args.File, m, libName, isTestOnly, &res)
 	}
 
 	// We add special packages to point to testonly libraries which - this accumulates them,
@@ -450,12 +464,16 @@ func (l javaLang) generateJavaLibrary(file *rule.File, pathToPackageRelativeToBa
 	res.Imports = append(res.Imports, resolveInput)
 }
 
-func (l javaLang) generateJavaBinary(file *rule.File, m types.ClassName, libName string, res *language.GenerateResult) {
+func (l javaLang) generateJavaBinary(file *rule.File, m types.ClassName, libName string, testonly bool, res *language.GenerateResult) {
 	const ruleKind = "java_binary"
 	name := m.BareOuterClassName()
 	r := rule.NewRule("java_binary", name) // FIXME check collision on name
 	r.SetAttr("main_class", m.FullyQualifiedClassName())
 
+	if testonly {
+		r.SetAttr("testonly", true)
+	}
+
 	runtimeDeps := l.collectRuntimeDeps(ruleKind, name, file)
 	runtimeDeps.Add(label.Label{Name: libName, Relative: true})
 	r.SetAttr("runtime_deps", labelsToStrings(runtimeDeps.SortedSlice()))

java/gazelle/testdata/bin_in_test_tree/BUILD.in

@@ -0,0 +1 @@
+# gazelle:resolve java org.junit @maven//:junit_junit

java/gazelle/testdata/bin_in_test_tree/BUILD.out

@@ -0,0 +1 @@
+# gazelle:resolve java org.junit @maven//:junit_junit

java/gazelle/testdata/bin_in_test_tree/expectedStderr.txt

@@ -0,0 +1 @@
+{"level":"warn","_c":"maven-resolver","error":"open %WORKSPACEPATH%/maven_install.json: no such file or directory","message":"not loading maven dependencies"}

java/gazelle/testdata/bin_in_test_tree/src/test/java/com/example/test/BUILD.out

@@ -0,0 +1,19 @@
+load("@rules_java//java:defs.bzl", "java_binary")
+load("@contrib_rules_jvm//java:defs.bzl", "java_test_suite")
+
+java_binary(
+    name = "SomeTestBinary",
+    testonly = True,
+    main_class = "com.example.test.SomeTestBinary",
+    visibility = ["//visibility:public"],
+    runtime_deps = [":test-test-lib"],
+)
+
+java_test_suite(
+    name = "test",
+    srcs = [
+        "SomeOtherTest.java",
+        "SomeTestBinary.java",
+    ],
+    deps = ["@maven//:junit_junit"],
+)

java/gazelle/testdata/bin_in_test_tree/src/test/java/com/example/test/SomeOtherTest.java

@@ -0,0 +1,8 @@
+package com.example.test;
+
+import org.junit.Test;
+
+public class SomeOtherTest {
+  @Test
+  public void testPasses() {}
+}

java/gazelle/testdata/bin_in_test_tree/src/test/java/com/example/test/SomeTestBinary.java

@@ -0,0 +1,7 @@
+package com.example.test;
+
+public class SomeTestBinary {
+  public static void main(String[] args) {
+    System.out.println("Test passed!");
+  }
+}