libtest: add --show-output option

this new flag enables printing the captured stdout of successful tests
utilizing the already existing display_output test runner option

src/librustdoc/markdown.rs

@@ -154,6 +154,6 @@ pub fn test(mut options: Options, diag: &errors::Handler) -> i32 {
 
     options.test_args.insert(0, "rustdoctest".to_string());
     testing::test_main(&options.test_args, collector.tests,
-                       testing::Options::new().display_output(options.display_warnings));
+                       Some(testing::Options::new().display_output(options.display_warnings)));
     0
 }

src/librustdoc/test.rs

@@ -120,7 +120,7 @@ pub fn run(options: Options) -> i32 {
     testing::test_main(
         &test_args,
         tests,
-        testing::Options::new().display_output(display_warnings)
+        Some(testing::Options::new().display_output(display_warnings))
     );
 
     0

src/libtest/lib.rs

@@ -272,7 +272,7 @@ impl Options {
 
 // The default console test runner. It accepts the command line
 // arguments and a vector of test_descs.
-pub fn test_main(args: &[String], tests: Vec<TestDescAndFn>, options: Options) {
+pub fn test_main(args: &[String], tests: Vec<TestDescAndFn>, options: Option<Options>) {
     let mut opts = match parse_opts(args) {
         Some(Ok(o)) => o,
         Some(Err(msg)) => {
@@ -281,8 +281,9 @@ pub fn test_main(args: &[String], tests: Vec<TestDescAndFn>, options: Options) {
         }
         None => return,
     };
-
-    opts.options = options;
+    if let Some(options) = options {
+        opts.options = options;
+    }
     if opts.list {
         if let Err(e) = list_tests_console(&opts, tests) {
             eprintln!("error: io error when listing tests: {:?}", e);
@@ -323,7 +324,7 @@ pub fn test_main_static(tests: &[&TestDescAndFn]) {
             _ => panic!("non-static tests passed to test::test_main_static"),
         })
         .collect();
-    test_main(&args, owned_tests, Options::new())
+    test_main(&args, owned_tests, None)
 }
 
 /// Invoked when unit tests terminate. Should panic if the unit
@@ -468,6 +469,11 @@ fn optgroups() -> getopts::Options {
             json   = Output a json document",
             "pretty|terse|json",
         )
+        .optflag(
+            "",
+            "show-output",
+            "Show captured stdout of successful tests"
+        )
         .optopt(
             "Z",
             "",
@@ -667,7 +673,7 @@ pub fn parse_opts(args: &[String]) -> Option<OptRes> {
         format,
         test_threads,
         skip: matches.opt_strs("skip"),
-        options: Options::new(),
+        options: Options::new().display_output(matches.opt_present("show-output")),
     };
 
     Some(Ok(test_opts))

src/libtest/tests.rs

@@ -160,6 +160,17 @@ fn parse_ignored_flag() {
     assert_eq!(opts.run_ignored, RunIgnored::Only);
 }
 
+#[test]
+fn parse_show_output_flag() {
+    let args = vec![
+        "progname".to_string(),
+        "filter".to_string(),
+        "--show-output".to_string(),
+    ];
+    let opts = parse_opts(&args).unwrap().unwrap();
+    assert!(opts.options.display_output);
+}
+
 #[test]
 fn parse_include_ignored_flag() {
     let args = vec![