Use freopen to move /dev/tty input to stdin so rustyline works when p…

…iping in input. (#32)

CHANGELOG.md

@@ -6,6 +6,11 @@ New features / changes:
   node, rather than moving down a line. (Functionality was previous
   available via `i`, but was undocumented; `i` has become unmapped.)
 
+Bug Fixes:
+- [Issue #7 / PR #32]: Fix issue with rustyline always reading from
+  STDIN preventing `/` command from working when input provided via
+  STDIN.
+
 Internal:
 - [PR #17]: Upgrade from structopt to clap v3
 

Cargo.toml

@@ -24,3 +24,4 @@ signal-hook = "0.3.8"
 libc = "0.2"
 clap = { version = "3.0", features = ["derive"] }
 isatty = "0.1"
+libc-stdhandle = "0.1.0"

src/input.rs

@@ -2,9 +2,8 @@ use signal_hook::consts::SIGWINCH;
 use signal_hook::low_level::pipe;
 use termion::event::{parse_event, Event, Key, MouseEvent};
 
-use std::fs::File;
 use std::io;
-use std::io::Read;
+use std::io::{stdin, Read, Stdin};
 use std::os::unix::io::AsRawFd;
 use std::os::unix::net::UnixStream;
 
@@ -15,13 +14,29 @@ const BUFFER_SIZE: usize = 1024;
 const ESCAPE: u8 = 0o33;
 
 pub fn get_input() -> impl Iterator<Item = io::Result<TuiEvent>> {
-    let tty = File::open("/dev/tty").unwrap();
+    // The readline library we use, rustyline, always gets its input from STDIN.
+    // If jless accepts its input from STDIN, then rustyline can't accept input.
+    // To fix this, we open up /dev/tty, and remap it to STDIN, as suggested in
+    // this StackOverflow post:
+    //
+    // https://stackoverflow.com/questions/29689034/piped-stdin-and-keyboard-same-time-in-c
+    //
+    // rustyline may add its own fix to support reading from /dev/tty:
+    //
+    // https://github.com/kkawakam/rustyline/issues/599
+    unsafe {
+        // freopen(3) docs: https://linux.die.net/man/3/freopen
+        let filename = std::ffi::CString::new("/dev/tty").unwrap();
+        let path = std::ffi::CString::new("r").unwrap();
+        let _ = libc::freopen(filename.as_ptr(), path.as_ptr(), libc_stdhandle::stdin());
+    }
+
     let (sigwinch_read, sigwinch_write) = UnixStream::pair().unwrap();
     pipe::register(SIGWINCH, sigwinch_write).unwrap();
-    TuiInput::new(tty, sigwinch_read)
+    TuiInput::new(stdin(), sigwinch_read)
 }
 
-fn read_and_retry_on_interrupt(input: &mut File, buf: &mut [u8]) -> io::Result<usize> {
+fn read_and_retry_on_interrupt(input: &mut Stdin, buf: &mut [u8]) -> io::Result<usize> {
     loop {
         match input.read(buf) {
             res @ Ok(_) => {
@@ -38,15 +53,15 @@ fn read_and_retry_on_interrupt(input: &mut File, buf: &mut [u8]) -> io::Result<u
 }
 
 struct BufferedInput<const N: usize> {
-    input: File,
+    input: Stdin,
     buffer: [u8; N],
     buffer_size: usize,
     buffer_index: usize,
     might_have_more_data: bool,
 }
 
 impl<const N: usize> BufferedInput<N> {
-    fn new(input: File) -> BufferedInput<N> {
+    fn new(input: Stdin) -> BufferedInput<N> {
         BufferedInput {
             input,
             buffer: [0; N],
@@ -136,7 +151,7 @@ struct TuiInput {
 }
 
 impl TuiInput {
-    fn new(input: File, sigwinch_pipe: UnixStream) -> TuiInput {
+    fn new(input: Stdin, sigwinch_pipe: UnixStream) -> TuiInput {
         let sigwinch_fd = sigwinch_pipe.as_raw_fd();
         let stdin_fd = input.as_raw_fd();
 

src/main.rs

@@ -3,6 +3,7 @@
 #![allow(clippy::collapsible_else_if)]
 
 extern crate lazy_static;
+extern crate libc_stdhandle;
 
 use std::fs::File;
 use std::io;
@@ -49,9 +50,16 @@ fn main() {
         std::process::exit(0);
     }
 
+    // Create our input *before* constructing the App. When we get the input,
+    // we use freopen to remap /dev/tty to STDIN so that rustyline works when
+    // JSON input is provided via STDIN. rustyline gets initialized when we
+    // create the App, so by putting this before, we make sure rustyline gets
+    // the /dev/tty input.
+    let input = Box::new(input::get_input());
     let stdout = MouseTerminal::from(HideCursor::from(AlternateScreen::from(
         io::stdout().into_raw_mode().unwrap(),
     )));
+
     let mut app = match App::new(&opt, json_string, input_filename, Box::new(stdout)) {
         Ok(jl) => jl,
         Err(err) => {
@@ -60,7 +68,7 @@ fn main() {
         }
     };
 
-    app.run(Box::new(input::get_input()));
+    app.run(input);
 }
 
 fn print_pretty_printed_json(json: String) {