feat(unstable): add Deno.consoleSize (#6520)

5 files changed, 115 insertions, 3 deletions

diff --git a/cli/js/deno_unstable.ts b/cli/js/deno_unstable.ts
index 7d75c1c6a..f92d767b3 100644
--- a/cli/js/deno_unstable.ts
+++ b/cli/js/deno_unstable.ts
@@ -12,7 +12,7 @@ export { openPlugin } from "./ops/plugins.ts";
 export { transpileOnly, compile, bundle } from "./compiler_api.ts";
 export { applySourceMap, formatDiagnostics } from "./ops/errors.ts";
 export { signal, signals, Signal, SignalStream } from "./signals.ts";
-export { setRaw } from "./ops/tty.ts";
+export { setRaw, consoleSize } from "./ops/tty.ts";
 export { utimeSync, utime } from "./ops/fs/utime.ts";
 export { ftruncateSync, ftruncate } from "./ops/fs/truncate.ts";
 export { shutdown, ShutdownMode } from "./net.ts";
diff --git a/cli/js/lib.deno.unstable.d.ts b/cli/js/lib.deno.unstable.d.ts
index f237cd4be..a6547ebca 100644
--- a/cli/js/lib.deno.unstable.d.ts
+++ b/cli/js/lib.deno.unstable.d.ts
@@ -43,6 +43,21 @@ declare namespace Deno {
    * Requires `allow-read` and `allow-write` permissions. */
   export function link(oldpath: string, newpath: string): Promise<void>;
 
+  /** **UNSTABLE**: New API, yet to be vetted.
+   *
+   * Gets the size of the console as columns/rows.
+   *
+   * ```ts
+   * const { columns, rows } = await Deno.consoleSize(Deno.stdout.rid);
+   * ```
+   */
+  export function consoleSize(
+    rid: number
+  ): {
+    columns: number;
+    rows: number;
+  };
+
   export type SymlinkOptions = {
     type: "file" | "dir";
   };
diff --git a/cli/js/ops/tty.ts b/cli/js/ops/tty.ts
index 8899ca5b8..f9da7bd0d 100644
--- a/cli/js/ops/tty.ts
+++ b/cli/js/ops/tty.ts
@@ -2,6 +2,10 @@
 
 import { sendSync } from "./dispatch_json.ts";
 
+export function consoleSize(rid: number): [number, number] {
+  return sendSync("op_console_size", { rid });
+}
+
 export function isatty(rid: number): boolean {
   return sendSync("op_isatty", { rid });
 }
diff --git a/cli/ops/tty.rs b/cli/ops/tty.rs
index bf94ec17f..d86100232 100644
--- a/cli/ops/tty.rs
+++ b/cli/ops/tty.rs
@@ -8,7 +8,7 @@ use deno_core::CoreIsolateState;
 use deno_core::ZeroCopyBuf;
 #[cfg(unix)]
 use nix::sys::termios;
-use serde_derive::Deserialize;
+use serde_derive::{Deserialize, Serialize};
 use serde_json::Value;
 
 #[cfg(windows)]
@@ -38,6 +38,7 @@ fn get_windows_handle(
 pub fn init(i: &mut CoreIsolate, s: &State) {
   i.register_op("op_set_raw", s.stateful_json_op2(op_set_raw));
   i.register_op("op_isatty", s.stateful_json_op2(op_isatty));
+  i.register_op("op_console_size", s.stateful_json_op2(op_console_size));
 }
 
 #[derive(Deserialize)]
@@ -250,3 +251,80 @@ pub fn op_isatty(
     })?;
   Ok(JsonOp::Sync(json!(isatty)))
 }
+
+#[derive(Deserialize)]
+struct ConsoleSizeArgs {
+  rid: u32,
+}
+
+#[derive(Serialize)]
+struct ConsoleSize {
+  columns: u32,
+  rows: u32,
+}
+
+pub fn op_console_size(
+  isolate_state: &mut CoreIsolateState,
+  state: &State,
+  args: Value,
+  _zero_copy: &mut [ZeroCopyBuf],
+) -> Result<JsonOp, OpError> {
+  state.check_unstable("Deno.consoleSize");
+  let args: ConsoleSizeArgs = serde_json::from_value(args)?;
+  let rid = args.rid;
+
+  let mut resource_table = isolate_state.resource_table.borrow_mut();
+  let size =
+    std_file_resource(&mut resource_table, rid as u32, move |r| match r {
+      Ok(std_file) => {
+        #[cfg(windows)]
+        {
+          use std::os::windows::io::AsRawHandle;
+          let handle = std_file.as_raw_handle();
+
+          unsafe {
+            let mut bufinfo: winapi::um::wincon::CONSOLE_SCREEN_BUFFER_INFO =
+              std::mem::zeroed();
+
+            if winapi::um::wincon::GetConsoleScreenBufferInfo(
+              handle,
+              &mut bufinfo,
+            ) == 0
+            {
+              // TODO (caspervonb) use GetLastError
+              return Err(OpError::other(
+                winapi::um::errhandlingapi::GetLastError().to_string(),
+              ));
+            }
+
+            Ok(ConsoleSize {
+              columns: bufinfo.dwSize.X as u32,
+              rows: bufinfo.dwSize.Y as u32,
+            })
+          }
+        }
+
+        #[cfg(unix)]
+        {
+          use std::os::unix::io::AsRawFd;
+
+          let fd = std_file.as_raw_fd();
+          unsafe {
+            let mut size: libc::winsize = std::mem::zeroed();
+            if libc::ioctl(fd, libc::TIOCGWINSZ, &mut size as *mut _) != 0 {
+              return Err(OpError::from(std::io::Error::last_os_error()));
+            }
+
+            // TODO (caspervonb) return a tuple instead
+            Ok(ConsoleSize {
+              columns: size.ws_col as u32,
+              rows: size.ws_row as u32,
+            })
+          }
+        }
+      }
+      Err(_) => Err(OpError::bad_resource_id()),
+    })?;
+
+  Ok(JsonOp::Sync(json!(size)))
+}
diff --git a/cli/tests/unit/tty_test.ts b/cli/tests/unit/tty_test.ts
index 116b0dfe9..7e9873791 100644
--- a/cli/tests/unit/tty_test.ts
+++ b/cli/tests/unit/tty_test.ts
@@ -1,8 +1,23 @@
 // Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
-import { unitTest, assert } from "./test_util.ts";
+import { unitTest, assert, assertThrows } from "./test_util.ts";
 
 // Note tests for Deno.setRaw is in integration tests.
 
+unitTest({ perms: { read: true } }, function consoleSizeFile(): void {
+  const file = Deno.openSync("cli/tests/hello.txt");
+  assertThrows(() => {
+    Deno.consoleSize(file.rid);
+  }, Error);
+  file.close();
+});
+
+unitTest(function consoleSizeError(): void {
+  assertThrows(() => {
+    // Absurdly large rid.
+    Deno.consoleSize(0x7fffffff);
+  }, Deno.errors.BadResource);
+});
+
 unitTest({ perms: { read: true } }, function isatty(): void {
   // CI not under TTY, so cannot test stdin/stdout/stderr.
   const f = Deno.openSync("cli/tests/hello.txt");