Make `--check` work when running from stdin. (#3896)

# Conflicts:
#	src/bin/main.rs

1 files changed, 93 insertions, 0 deletions

diff --git a/src/test/mod.rs b/src/test/mod.rs
index cceb28dfea6..e1a7972ec82 100644
--- a/src/test/mod.rs
+++ b/src/test/mod.rs
@@ -307,6 +307,52 @@ fn assert_output(source: &Path, expected_filename: &Path) {
     }
 }
 
+// Helper function for comparing the results of rustfmt
+// to a known output generated by one of the write modes.
+fn assert_stdin_output(
+    source: &Path,
+    expected_filename: &Path,
+    emit_mode: EmitMode,
+    has_diff: bool,
+) {
+    let mut config = Config::default();
+    config.set().newline_style(NewlineStyle::Unix);
+    config.set().emit_mode(emit_mode);
+
+    let mut source_file = fs::File::open(&source).expect("couldn't open source");
+    let mut source_text = String::new();
+    source_file
+        .read_to_string(&mut source_text)
+        .expect("Failed reading target");
+    let input = Input::Text(source_text);
+
+    // Populate output by writing to a vec.
+    let mut buf: Vec<u8> = vec![];
+    {
+        let mut session = Session::new(config, Some(&mut buf));
+        session.format(input).unwrap();
+        let errors = ReportedErrors {
+            has_diff: has_diff,
+            ..Default::default()
+        };
+        assert_eq!(session.errors, errors);
+    }
+
+    let mut expected_file = fs::File::open(&expected_filename).expect("couldn't open target");
+    let mut expected_text = String::new();
+    expected_file
+        .read_to_string(&mut expected_text)
+        .expect("Failed reading target");
+
+    let output = String::from_utf8(buf).unwrap();
+    let compare = make_diff(&expected_text, &output, DIFF_CONTEXT_SIZE);
+    if !compare.is_empty() {
+        let mut failures = HashMap::new();
+        failures.insert(source.to_owned(), compare);
+        print_mismatches_default_message(failures);
+        panic!("Text does not match expected output");
+    }
+}
 // Idempotence tests. Files in tests/target are checked to be unaltered by
 // rustfmt.
 #[nightly_only_test]
@@ -463,6 +509,30 @@ fn stdin_works_with_modified_lines() {
     assert_eq!(buf, output.as_bytes());
 }
 
+/// Ensures that `EmitMode::Json` works with input from `stdin`.
+#[test]
+fn stdin_works_with_json() {
+    init_log();
+    assert_stdin_output(
+        Path::new("tests/writemode/source/stdin.rs"),
+        Path::new("tests/writemode/target/stdin.json"),
+        EmitMode::Json,
+        true,
+    );
+}
+
+/// Ensures that `EmitMode::Checkstyle` works with input from `stdin`.
+#[test]
+fn stdin_works_with_checkstyle() {
+    init_log();
+    assert_stdin_output(
+        Path::new("tests/writemode/source/stdin.rs"),
+        Path::new("tests/writemode/target/stdin.xml"),
+        EmitMode::Checkstyle,
+        false,
+    );
+}
+
 #[test]
 fn stdin_disable_all_formatting_test() {
     init_log();
@@ -896,3 +966,26 @@ fn verify_check_works() {
         .status()
         .expect("run with check option failed");
 }
+
+#[test]
+fn verify_check_works_with_stdin() {
+    init_log();
+
+    let mut child = Command::new(rustfmt().to_str().unwrap())
+        .arg("--check")
+        .stdin(Stdio::piped())
+        .stderr(Stdio::piped())
+        .spawn()
+        .expect("run with check option failed");
+
+    {
+        let stdin = child.stdin.as_mut().expect("Failed to open stdin");
+        stdin
+            .write_all("fn main() {}\n".as_bytes())
+            .expect("Failed to write to rustfmt --check");
+    }
+    let output = child
+        .wait_with_output()
+        .expect("Failed to wait on rustfmt child");
+    assert!(output.status.success());
+}