Make orchard.java.parser-utils/parse-java-test more easily debuggable

We used to return nil for invalid .java source code.

Now we throw an exception, with the parsing error diagnostics as part of the ex-data.

Note that this doesn't change user-facing behavior, since all exceptions are caught by default in `orchard.java.parser/source-info` / `orchard.java.parser-next/source-info`.

This helps debug faulty .java source code, see e.g. aws/aws-sdk-java#3045

project.clj

@@ -55,6 +55,7 @@
                                    [nubank/matcher-combinators "3.8.8"]]
                     :resource-paths ["test-resources"
                                      "not-a.jar"
+                                     "test-java-invalid"
                                      "does-not-exist.jar"]
                     :java-source-paths ["test-java"]
                     ;; Initialize the cache verbosely, as usual, so that possible issues can be more easily diagnosed:

src-newer-jdks/orchard/java/parser_utils.clj

@@ -8,7 +8,7 @@
   (:import
    (java.io StringWriter)
    (javax.lang.model.element VariableElement)
-   (javax.tools ToolProvider)
+   (javax.tools DocumentationTool DocumentationTool$DocumentationTask ToolProvider)
    (jdk.javadoc.doclet Doclet DocletEnvironment)))
 
 (def result (atom nil))
@@ -19,7 +19,7 @@
   (when-let [res (io/resource path)]
     (let [tmpdir   (System/getProperty "java.io.tmpdir")
           tmpfile  (io/file tmpdir (.getName (io/file path)))
-          compiler (ToolProvider/getSystemDocumentationTool)
+          ^DocumentationTool compiler (ToolProvider/getSystemDocumentationTool)
           sources  (-> (.getStandardFileManager compiler nil nil nil)
                        (.getJavaFileObjectsFromFiles [tmpfile]))
           doclet   (class (reify Doclet
@@ -39,11 +39,19 @@
                                 "--show-module-contents" "all"
                                 "-quiet"]
                           (when module
-                            ["--patch-module" (str module "=" tmpdir)]))]
-      (spit tmpfile (slurp res))
-      (.call (.getTask compiler out nil nil doclet opts sources))
-      (.delete tmpfile)
-      @result)))
+                            ["--patch-module" (str module "=" tmpdir)]))
+          slurped (slurp res)
+          _ (spit tmpfile slurped)
+          ^DocumentationTool$DocumentationTask task (.getTask compiler out nil nil doclet opts sources)]
+      (try
+        (if (false? (.call task))
+          (throw (ex-info "Failed to parse Java source code"
+                          {:path path
+                           :module module
+                           :out (str out)}))
+          @result)
+        (finally
+          (.delete tmpfile))))))
 
 ;;; ## Java Parse Tree Traversal
 ;;

test-java-invalid/orchard/java/UnderscoreClass.java

@@ -0,0 +1,10 @@
+package orchard.java;
+
+public class UnderscoreClass {
+
+    public UnderscoreClass(){
+        // Uses an underscore as identifier, which is no longer valid Java source code:
+        int _ = 52;
+    }
+
+}

test-newer-jdks/orchard/java/parser_next_test.clj

@@ -4,13 +4,24 @@
    [clojure.test :refer [deftest is testing]]
    [orchard.java :as java]
    [orchard.java.parser-next :as sut]
+   [orchard.java.parser-utils :as parser-utils]
    [orchard.test.util :as util])
   (:import
    (orchard.java DummyClass)))
 
 (when (System/getenv "CI")
   (println "has-enriched-classpath?" (pr-str util/has-enriched-classpath?)))
 
+(when @@java/parser-next-available?
+  (deftest parse-java-test
+    (testing "Throws an informative exception on invalid code"
+      (try
+        (parser-utils/parse-java "orchard/java/UnderscoreClass.java"
+                                 nil)
+        (assert false)
+        (catch Exception e
+          (is (-> e ex-data :out (string/includes? "'_' is a keyword, and may not be used as an identifier"))))))))
+
 (when (and util/has-enriched-classpath?
            @@java/parser-next-available?)
   (deftest source-info-test