fmt: deno fmt - formats stdin and print to stdout (#3920)

cli/flags.rs

@@ -550,7 +550,10 @@ fn fmt_subcommand<'a, 'b>() -> App<'a, 'b> {
 
   deno fmt myfile1.ts myfile2.ts
 
-  deno fmt --check",
+  deno fmt --check
+
+  # Format stdin and write to stdout
+  cat file.ts | deno fmt -",
     )
     .arg(
       Arg::with_name("check")
@@ -1390,6 +1393,18 @@ mod tests {
         ..DenoFlags::default()
       }
     );
+
+    let r = flags_from_vec_safe(svec!["deno", "fmt"]);
+    assert_eq!(
+      r.unwrap(),
+      DenoFlags {
+        subcommand: DenoSubcommand::Format {
+          check: false,
+          files: None
+        },
+        ..DenoFlags::default()
+      }
+    );
   }
 
   #[test]

cli/fmt.rs

@@ -7,10 +7,17 @@
 //! the future it can be easily extended to provide
 //! the same functions as ops available in JS runtime.
 
+use crate::deno_error::DenoError;
+use crate::deno_error::ErrorKind;
+use deno_core::ErrBox;
 use dprint_plugin_typescript as dprint;
 use glob;
 use regex::Regex;
 use std::fs;
+use std::io::stdin;
+use std::io::stdout;
+use std::io::Read;
+use std::io::Write;
 use std::path::Path;
 use std::path::PathBuf;
 use std::time::Instant;
@@ -157,9 +164,29 @@ fn get_matching_files(glob_paths: Vec<String>) -> Vec<PathBuf> {
 ///
 /// First argument supports globs, and if it is `None`
 /// then the current directory is recursively walked.
-pub fn format_files(maybe_files: Option<Vec<String>>, check: bool) {
+pub fn format_files(
+  maybe_files: Option<Vec<String>>,
+  check: bool,
+) -> Result<(), ErrBox> {
   // TODO: improve glob to look for tsx?/jsx? files only
   let glob_paths = maybe_files.unwrap_or_else(|| vec!["**/*".to_string()]);
+
+  for glob_path in glob_paths.iter() {
+    if glob_path == "-" {
+      // If the only given path is '-', format stdin.
+      if glob_paths.len() == 1 {
+        format_stdin(check);
+      } else {
+        // Otherwise it is an error
+        return Err(ErrBox::from(DenoError::new(
+          ErrorKind::Other,
+          "Ambiguous filename input. To format stdin, provide a single '-' instead.".to_owned()
+        )));
+      }
+      return Ok(());
+    }
+  }
+
   let matching_files = get_matching_files(glob_paths);
   let matching_files = get_supported_files(matching_files);
   let config = get_config();
@@ -169,4 +196,38 @@ pub fn format_files(maybe_files: Option<Vec<String>>, check: bool) {
   } else {
     format_source_files(config, matching_files);
   }
+
+  Ok(())
+}
+
+/// Format stdin and write result to stdout.
+/// Treats input as TypeScript.
+/// Compatible with `--check` flag.
+fn format_stdin(check: bool) {
+  let mut source = String::new();
+  if stdin().read_to_string(&mut source).is_err() {
+    eprintln!("Failed to read from stdin");
+  }
+  let config = get_config();
+
+  match dprint::format_text("_stdin.ts", &source, &config) {
+    Ok(None) => {
+      // Should not happen.
+      unreachable!();
+    }
+    Ok(Some(formatted_text)) => {
+      if check {
+        if formatted_text != source {
+          println!("Not formatted stdin");
+        }
+      } else {
+        let _r = stdout().write_all(formatted_text.as_bytes());
+        // TODO(ry) Only ignore SIGPIPE. Currently ignoring all errors.
+      }
+    }
+    Err(e) => {
+      eprintln!("Error formatting from stdin");
+      eprintln!("   {}", e);
+    }
+  }
 }

cli/lib.rs

@@ -405,7 +405,9 @@ async fn run_script(flags: DenoFlags, script: String) {
 }
 
 async fn fmt_command(files: Option<Vec<String>>, check: bool) {
-  fmt::format_files(files, check);
+  if let Err(err) = fmt::format_files(files, check) {
+    print_err_and_exit(err);
+  }
 }
 
 pub fn main() {

cli/tests/integration_tests.rs

@@ -603,6 +603,32 @@ itest!(bundle {
   output: "bundle.test.out",
 });
 
+itest!(fmt_stdin {
+  args: "fmt -",
+  input: Some("const a = 1\n"),
+  output_str: Some("const a = 1;\n"),
+});
+
+itest!(fmt_stdin_ambiguous {
+  args: "fmt - file.ts",
+  input: Some("const a = 1\n"),
+  check_stderr: true,
+  exit_code: 1,
+  output_str: Some("Ambiguous filename input. To format stdin, provide a single '-' instead.\n"),
+});
+
+itest!(fmt_stdin_check_formatted {
+  args: "fmt --check -",
+  input: Some("const a = 1;\n"),
+  output_str: Some(""),
+});
+
+itest!(fmt_stdin_check_not_formatted {
+  args: "fmt --check -",
+  input: Some("const a = 1\n"),
+  output_str: Some("Not formatted stdin\n"),
+});
+
 itest!(circular1 {
   args: "run --reload circular1.js",
   output: "circular1.js.out",
@@ -917,6 +943,7 @@ mod util {
     pub args: &'static str,
     pub output: &'static str,
     pub input: Option<&'static str>,
+    pub output_str: Option<&'static str>,
     pub exit_code: i32,
     pub check_stderr: bool,
     pub http_server: bool,
@@ -982,10 +1009,13 @@ mod util {
         );
       }
 
-      let output_path = tests_dir.join(self.output);
-      println!("output path {}", output_path.display());
-      let expected =
-        std::fs::read_to_string(output_path).expect("cannot read output");
+      let expected = if let Some(s) = self.output_str {
+        s.to_owned()
+      } else {
+        let output_path = tests_dir.join(self.output);
+        println!("output path {}", output_path.display());
+        std::fs::read_to_string(output_path).expect("cannot read output")
+      };
 
       if !wildcard_match(&expected, &actual) {
         println!("OUTPUT\n{}\nOUTPUT", actual);