clif-util: add option for controlling terminal colors

On @fitzgen's suggestion, this change adds a `--color` option for controlling whether the `clif-util` output prints with ANSI color escape sequences. Only `clif-util wasm ...` currently uses this new option. The option has three variants:
 - `--color auto`, the default, prints colors if the terminal supports them
 - `--color always` prints colors always
 - `--color never` never prints colors

cranelift/src/clif-util.rs

@@ -13,7 +13,7 @@
     )
 )]
 
-use clap::{App, Arg, SubCommand};
+use clap::{arg_enum, App, Arg, SubCommand};
 use cranelift_codegen::dbg::LOG_FILENAME_PREFIX;
 use cranelift_codegen::VERSION;
 use std::io::{self, Write};
@@ -62,6 +62,26 @@ fn add_verbose_flag<'a>() -> clap::Arg<'a, 'a> {
     Arg::with_name("verbose").short("v").help("Be more verbose")
 }
 
+arg_enum! {
+    #[derive(Clone, Copy, Debug, PartialEq)]
+    pub enum UseTerminalColor {
+        Auto,
+        Never,
+        Always
+    }
+}
+
+fn add_color<'a>() -> clap::Arg<'a, 'a> {
+    Arg::with_name("color")
+        .long("color")
+        .possible_values(&UseTerminalColor::variants())
+        .takes_value(true)
+        .multiple(false)
+        .default_value("auto")
+        .case_insensitive(true)
+        .help("Use colors in output")
+}
+
 fn add_time_flag<'a>() -> clap::Arg<'a, 'a> {
     Arg::with_name("time-passes")
         .short("T")
@@ -120,6 +140,12 @@ fn add_check_translation_flag<'a>() -> clap::Arg<'a, 'a> {
         .help("Just checks the correctness of Cranelift IR translated from WebAssembly")
 }
 
+fn add_value_ranges<'a>() -> clap::Arg<'a, 'a> {
+    Arg::with_name("value-ranges")
+        .long("value-ranges")
+        .help("Display values ranges and their locations")
+}
+
 /// Returns a vector of clap value options and changes these options into a vector of strings
 fn get_vec(argument_vec: Option<clap::Values>) -> Vec<String> {
     let mut ret_vec: Vec<String> = Vec::new();
@@ -201,11 +227,9 @@ fn main() {
         )
         .subcommand(add_wasm_or_compile("compile"))
         .subcommand(
-            add_wasm_or_compile("wasm").arg(
-                Arg::with_name("value-ranges")
-                    .long("value-ranges")
-                    .help("Display values ranges and their locations"),
-            ),
+            add_wasm_or_compile("wasm")
+                .arg(add_value_ranges())
+                .arg(add_color()),
         )
         .subcommand(
             SubCommand::with_name("pass")
@@ -306,6 +330,7 @@ fn main() {
 
                 wasm::run(
                     get_vec(rest_cmd.values_of("file")),
+                    rest_cmd.value_of("color").unwrap().parse().unwrap(),
                     rest_cmd.is_present("verbose"),
                     rest_cmd.is_present("just-decode"),
                     rest_cmd.is_present("check-translation"),

cranelift/src/wasm.rs

@@ -9,6 +9,7 @@
 
 use crate::disasm::{print_all, PrintRelocs, PrintStackmaps, PrintTraps};
 use crate::utils::parse_sets_and_triple;
+use crate::UseTerminalColor;
 use cranelift_codegen::ir::DisplayFunctionAnnotations;
 use cranelift_codegen::print_errors::{pretty_error, pretty_verifier_error};
 use cranelift_codegen::settings::FlagsOrIsa;
@@ -31,27 +32,36 @@ macro_rules! vprintln {
 }
 /// For verbose printing: prints in color if the `$x` expression is true.
 macro_rules! vcprintln {
-    ($x: expr, $term: ident, $color: expr, $($tts:tt)*) => {
+    ($x: expr, $use_color: expr, $term: ident, $color: expr, $($tts:tt)*) => {
         if $x {
-            let _ = $term.fg($color);
+            if $use_color {
+                let _ = $term.fg($color);
+            }
             println!($($tts)*);
-            let _ = $term.reset();
+            if $use_color {
+                let _ = $term.reset();
+            }
         }
     };
 }
 /// For verbose printing: prints in color (without an appended newline) if the `$x` expression is true.
 macro_rules! vcprint {
-    ($x: expr, $term: ident, $color: expr, $($tts:tt)*) => {
+    ($x: expr, $use_color: expr, $term: ident, $color: expr, $($tts:tt)*) => {
         if $x {
-            let _ = $term.fg($color);
+            if $use_color {
+                let _ = $term.fg($color);
+            }
             print!($($tts)*);
-            let _ = $term.reset();
+            if $use_color {
+                let _ = $term.reset();
+            }
         }
     };
 }
 
 pub fn run(
     files: Vec<String>,
+    use_terminal_color: UseTerminalColor,
     flag_verbose: bool,
     flag_just_decode: bool,
     flag_check_translation: bool,
@@ -68,6 +78,7 @@ pub fn run(
         let path = Path::new(&filename);
         let name = String::from(path.as_os_str().to_string_lossy());
         handle_module(
+            use_terminal_color,
             flag_verbose,
             flag_just_decode,
             flag_check_translation,
@@ -85,6 +96,7 @@ pub fn run(
 }
 
 fn handle_module(
+    use_terminal_color: UseTerminalColor,
     flag_verbose: bool,
     flag_just_decode: bool,
     flag_check_translation: bool,
@@ -98,10 +110,19 @@ fn handle_module(
     fisa: FlagsOrIsa,
 ) -> Result<(), String> {
     let mut terminal = term::stdout().unwrap();
-    vcprint!(flag_verbose, terminal, term::color::YELLOW, "Handling: ");
+    let use_color = terminal.supports_color() && use_terminal_color == UseTerminalColor::Auto
+        || use_terminal_color == UseTerminalColor::Always;
+    vcprint!(
+        flag_verbose,
+        use_color,
+        terminal,
+        term::color::YELLOW,
+        "Handling: "
+    );
     vprintln!(flag_verbose, "\"{}\"", name);
     vcprint!(
         flag_verbose,
+        use_color,
         terminal,
         term::color::MAGENTA,
         "Translating... "
@@ -135,7 +156,7 @@ fn handle_module(
         DummyEnvironment::new(isa.frontend_config(), ReturnMode::NormalReturns, debug_info);
     translate_module(&module_binary, &mut dummy_environ).map_err(|e| e.to_string())?;
 
-    vcprintln!(flag_verbose, terminal, term::color::GREEN, "ok");
+    vcprintln!(flag_verbose, use_color, terminal, term::color::GREEN, "ok");
 
     if flag_just_decode {
         if !flag_print {
@@ -166,10 +187,17 @@ fn handle_module(
     }
 
     if flag_check_translation {
-        vcprint!(flag_verbose, terminal, term::color::MAGENTA, "Checking... ");
+        vcprint!(
+            flag_verbose,
+            use_color,
+            terminal,
+            term::color::MAGENTA,
+            "Checking... "
+        );
     } else {
         vcprint!(
             flag_verbose,
+            use_color,
             terminal,
             term::color::MAGENTA,
             "Compiling... "
@@ -278,6 +306,6 @@ fn handle_module(
         println!("{}", timing::take_current());
     }
 
-    vcprintln!(flag_verbose, terminal, term::color::GREEN, "ok");
+    vcprintln!(flag_verbose, use_color, terminal, term::color::GREEN, "ok");
     Ok(())
 }