Echo back input from stdin when disable_all_formatting is true

src/lib.rs

@@ -881,6 +881,12 @@ pub fn format_input<T: Write>(
 ) -> Result<(Summary, FileMap, FormatReport), (io::Error, Summary)> {
     let mut summary = Summary::default();
     if config.disable_all_formatting() {
+        // When the input is from stdin, echo back the input.
+        if let Input::Text(ref buf) = input {
+            if let Err(e) = io::stdout().write_all(buf.as_bytes()) {
+                return Err((e, summary));
+            }
+        }
         return Ok((summary, FileMap::new(), FormatReport::new()));
     }
     let codemap = Rc::new(CodeMap::new(FilePathMapping::empty()));

tests/config/disable_all_formatting.toml

@@ -0,0 +1 @@
+disable_all_formatting = true

tests/system.rs

@@ -14,8 +14,9 @@ extern crate term;
 
 use std::collections::HashMap;
 use std::fs;
-use std::io::{self, BufRead, BufReader, Read};
+use std::io::{self, BufRead, BufReader, Read, Write};
 use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
 
 use rustfmt::*;
 use rustfmt::filemap::{write_system_newlines, FileMap};
@@ -157,6 +158,28 @@ fn stdin_formatting_smoke_test() {
     panic!("no stdin");
 }
 
+#[test]
+fn stdin_disable_all_formatting_test() {
+    let input = String::from("fn main() { println!(\"This should not be formatted.\"); }");
+    let mut child = Command::new("./target/debug/rustfmt")
+        .stdin(Stdio::piped())
+        .stdout(Stdio::piped())
+        .arg("--config-path=./tests/config/disable_all_formatting.toml")
+        .spawn()
+        .expect("failed to execute child");
+
+    {
+        let stdin = child.stdin.as_mut().expect("failed to get stdin");
+        stdin
+            .write_all(input.as_bytes())
+            .expect("failed to write stdin");
+    }
+    let output = child.wait_with_output().expect("failed to wait on child");
+    assert!(output.status.success());
+    assert!(output.stderr.is_empty());
+    assert_eq!(input, String::from_utf8(output.stdout).unwrap());
+}
+
 #[test]
 fn format_lines_errors_are_reported() {
     let long_identifier = String::from_utf8(vec![b'a'; 239]).unwrap();