blob: ab69e10b33372a3d7ce56c21cac45241919eefc8 [file] [log] [blame]
// Copyright (c) 2018, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
library front_end.terminal_color_support;
import 'dart:convert' show jsonEncode;
import 'dart:io' show Platform, Process, ProcessResult, stderr, stdout;
import 'package:_fe_analyzer_shared/src/messages/diagnostic_message.dart'
show DiagnosticMessage;
import 'package:_fe_analyzer_shared/src/util/colors.dart'
show ALL_CODES, TERMINAL_CAPABILITIES;
/// True if we should enable colors in output.
///
/// We enable colors only when both [stdout] and [stderr] support ANSI escapes.
final bool enableTerminalColors = _computeEnableColors();
void printDiagnosticMessage(
DiagnosticMessage message, void Function(String) println) {
if (enableTerminalColors) {
message.ansiFormatted.forEach(println);
} else {
message.plainTextFormatted.forEach(println);
}
}
/// On Windows, colors are enabled if both stdout and stderr supports ANSI
/// escapes. On other platforms, we rely on the external programs `tty` and
/// `tput` to compute if ANSI colors are supported.
bool _computeEnableColors() {
const bool debug =
const bool.fromEnvironment("front_end.debug_compute_enable_colors");
if (Platform.isWindows) {
if (!stdout.supportsAnsiEscapes || !stderr.supportsAnsiEscapes) {
// In this case, either [stdout] or [stderr] did not support the property
// `supportsAnsiEscapes`. Since we do not have another way to determine
// support for colors, we disable them.
if (debug) {
print("Not enabling colors as ANSI is not supported.");
}
return false;
}
if (debug) {
print("Enabling colors as OS is Windows.");
}
return true;
}
// We have to check if the terminal actually supports colors. Currently, to
// avoid linking the Dart VM with ncurses, ANSI escape support is reduced to
// `Platform.environment['TERM'].contains("xterm")`.
// Check if stdin is a terminal (TTY).
ProcessResult result =
Process.runSync("/bin/sh", ["-c", "tty > /dev/null 2> /dev/null"]);
if (result.exitCode != 0) {
if (debug) {
print("Not enabling colors, stdin isn't a terminal.");
}
return false;
}
// The `-S` option of `tput` allows us to query multiple capabilities at
// once.
result = Process.runSync(
"/bin/sh", ["-c", "printf '%s' '$TERMINAL_CAPABILITIES' | tput -S"]);
if (result.exitCode != 0) {
if (debug) {
print("Not enabling colors, running tput failed.");
}
return false;
}
List<String> lines = result.stdout.split("\n");
if (lines.length != 2) {
if (debug) {
print("Not enabling colors, unexpected output from tput: "
"${jsonEncode(result.stdout)}.");
}
return false;
}
String numberOfColors = lines[0];
if ((int.tryParse(numberOfColors) ?? -1) < 8) {
if (debug) {
print("Not enabling colors, less than 8 colors supported: "
"${jsonEncode(numberOfColors)}.");
}
return false;
}
String allCodes = lines[1].trim();
if (ALL_CODES != allCodes) {
if (debug) {
print("Not enabling colors, color codes don't match: "
"${jsonEncode(ALL_CODES)} != ${jsonEncode(allCodes)}.");
}
return false;
}
if (debug) {
print("Enabling colors.");
}
return true;
}