If stdout is not a TTY, print pretty printed JSON to stdout and exit.

src/main.rs

@@ -10,6 +10,7 @@ use termion::raw::IntoRawMode;
 use termion::screen::AlternateScreen;
 
 use jless::app::App;
+use jless::flatjson::{parse_top_level_json2, Value};
 use jless::input;
 use jless::options::Opt;
 
@@ -19,11 +20,16 @@ fn main() {
     let (json_string, input_filename) = match get_json_input(&opt) {
         Ok(json_string) => json_string,
         Err(err) => {
-            println!("Unable to get input: {}", err);
+            eprintln!("Unable to get input: {}", err);
             std::process::exit(1);
         }
     };
 
+    if !isatty::stdout_isatty() {
+        print_pretty_printed_json(json_string);
+        std::process::exit(0);
+    }
+
     let stdout = MouseTerminal::from(HideCursor::from(AlternateScreen::from(
         io::stdout().into_raw_mode().unwrap(),
     )));
@@ -38,6 +44,44 @@ fn main() {
     app.run(Box::new(input::get_input()));
 }
 
+fn print_pretty_printed_json(json: String) {
+    let flatjson = match jless::flatjson::parse_top_level_json2(json) {
+        Ok(flatjson) => flatjson,
+        Err(err) => {
+            eprintln!("Unable to parse input: {:?}", err);
+            std::process::exit(1);
+        }
+    };
+
+    for row in flatjson.0.iter() {
+        for _ in 0..row.depth {
+            print!("  ");
+        }
+        if let Some(ref key_range) = row.key_range {
+            print!("{}: ", &flatjson.1[key_range.clone()]);
+        }
+        let mut trailing_comma = row.parent.is_some() && row.next_sibling.is_some();
+        if let Some(container_type) = row.value.container_type() {
+            if row.value.is_opening_of_container() {
+                print!("{}", container_type.open_str());
+                // Don't print trailing commas after { or [.
+                trailing_comma = false;
+            } else {
+                print!("{}", container_type.close_str());
+                // Check container opening to see if we have a next sibling.
+                trailing_comma = row.parent.is_some()
+                    && flatjson.0[row.pair_index().unwrap()].next_sibling.is_some();
+            }
+        } else {
+            print!("{}", &flatjson.1[row.range.clone()]);
+        }
+        if trailing_comma {
+            print!(",");
+        }
+        println!("");
+    }
+}
+
 fn get_json_input(opt: &Opt) -> io::Result<(String, String)> {
     let mut json_string = String::new();
     let filename;