Add Colorize.default_enabled?

spec/std/colorize_spec.cr

@@ -1,5 +1,6 @@
 require "spec"
 require "colorize"
+require "../support/env"
 
 private def colorize(obj, *args)
   obj.colorize(*args).toggle(true)
@@ -17,7 +18,70 @@ private class ColorizeToS
   end
 end
 
+private class ColorizeTTY < IO
+  def tty? : Bool
+    true
+  end
+
+  def read(slice : Bytes)
+    0
+  end
+
+  def write(slice : Bytes) : Nil
+  end
+end
+
 describe "colorize" do
+  it ".default_enabled?" do
+    io = IO::Memory.new
+    tty = ColorizeTTY.new
+
+    with_env("TERM": nil, "NO_COLOR": nil) do
+      Colorize.default_enabled?(io).should be_false
+      Colorize.default_enabled?(tty).should be_true
+      Colorize.default_enabled?(io, io).should be_false
+      Colorize.default_enabled?(io, tty).should be_false
+      Colorize.default_enabled?(tty, io).should be_false
+      Colorize.default_enabled?(tty, tty).should be_true
+    end
+
+    with_env("TERM": nil, "NO_COLOR": "") do
+      Colorize.default_enabled?(io).should be_false
+      Colorize.default_enabled?(tty).should be_true
+      Colorize.default_enabled?(io, io).should be_false
+      Colorize.default_enabled?(io, tty).should be_false
+      Colorize.default_enabled?(tty, io).should be_false
+      Colorize.default_enabled?(tty, tty).should be_true
+    end
+
+    with_env("TERM": nil, "NO_COLOR": "1") do
+      Colorize.default_enabled?(io).should be_false
+      Colorize.default_enabled?(tty).should be_false
+      Colorize.default_enabled?(io, io).should be_false
+      Colorize.default_enabled?(io, tty).should be_false
+      Colorize.default_enabled?(tty, io).should be_false
+      Colorize.default_enabled?(tty, tty).should be_false
+    end
+
+    with_env("TERM": "xterm", "NO_COLOR": nil) do
+      Colorize.default_enabled?(io).should be_false
+      Colorize.default_enabled?(tty).should be_true
+      Colorize.default_enabled?(io, io).should be_false
+      Colorize.default_enabled?(io, tty).should be_false
+      Colorize.default_enabled?(tty, io).should be_false
+      Colorize.default_enabled?(tty, tty).should be_true
+    end
+
+    with_env("TERM": "dumb", "NO_COLOR": nil) do
+      Colorize.default_enabled?(io).should be_false
+      Colorize.default_enabled?(tty).should be_false
+      Colorize.default_enabled?(io, io).should be_false
+      Colorize.default_enabled?(io, tty).should be_false
+      Colorize.default_enabled?(tty, io).should be_false
+      Colorize.default_enabled?(tty, tty).should be_false
+    end
+  end
+
   it "colorizes without change" do
     colorize("hello").to_s.should eq("hello")
   end

src/colorize.cr

@@ -117,7 +117,8 @@
 #
 # See `Colorize::Mode` for available text decorations.
 module Colorize
-  # Objects will only be colored if this is `true`.
+  # Objects will only be colored if this is `true`, unless overridden by
+  # `Colorize::Object#toggle`.
   #
   # ```
   # require "colorize"
@@ -129,27 +130,33 @@ module Colorize
   # "hello".colorize.red.to_s # => "hello"
   # ```
   #
-  # NOTE: This is by default enabled according to `.on_tty_only!`.
-  class_property? enabled : Bool do
-    STDOUT.tty? && STDERR.tty? && ENV["TERM"]? != "dumb" && !ENV["NO_COLOR"]?.try(&.empty?.!)
-  end
+  # NOTE: This is by default enabled if `.default_enabled?` is true for `STDOUT`
+  # and `STDERR`.
+  class_property? enabled : Bool { default_enabled?(STDOUT, STDERR) }
 
-  # Makes `Colorize.enabled` `true` if and only if both of `STDOUT.tty?`
-  # and `STDERR.tty?` are `true` and the tty is not considered a dumb terminal.
-  # This is determined by the environment variable called `TERM`.
-  # If `TERM=dumb`, color won't be enabled.
-  # If `NO_COLOR` contains any non-empty value, color won't be enabled
-  # conforming to https://no-color.org
-  #
-  # Returns the new value of `Colorize.enabled?`.
+  # Resets `Colorize.enabled?` to its initial default value, i.e. whether
+  # `.default_enabled?` is true for `STDOUT` and `STDERR`. Returns this new
+  # value.
   #
-  # This can be used to revert `Colorize.enabled?` to its default value after
+  # This can be used to revert `Colorize.enabled?` to its initial state after
   # colorization is explicitly enabled or disabled.
   def self.on_tty_only! : Bool
     @@enabled = nil
     enabled?
   end
 
+  # Returns whether colorization should be enabled by default on the given
+  # standard output and error streams.
+  #
+  # This is true if both streams are terminals (i.e. `IO#tty?` returns true),
+  # the `TERM` environment variable is not equal to `dumb`, and the
+  # [`NO_COLOR` environment variable](https://no-color.org) is not set to a
+  # non-empty string.
+  def self.default_enabled?(stdout : IO, stderr : IO = stdout) : Bool
+    stdout.tty? && (stderr == stdout || stderr.tty?) &&
+      ENV["TERM"]? != "dumb" && !ENV["NO_COLOR"]?.try(&.empty?.!)
+  end
+
   # Resets the color and text decoration of the *io*.
   #
   # ```

src/compiler/crystal/command.cr

@@ -59,7 +59,7 @@ class Crystal::Command
   @compiler : Compiler?
 
   def initialize(@options : Array(String))
-    @color = ENV["TERM"]? != "dumb" && !ENV["NO_COLOR"]?.try(&.empty?.!)
+    @color = Colorize.default_enabled?(STDOUT, STDERR)
     @error_trace = false
     @progress_tracker = ProgressTracker.new
   end
@@ -762,7 +762,7 @@ class Crystal::Command
 
   private def error(msg, exit_code = 1)
     # This is for the case where the main command is wrong
-    @color = false if ARGV.includes?("--no-color") || ENV["TERM"]? == "dumb" || ENV["NO_COLOR"]?.try(&.empty?.!)
+    @color = false if ARGV.includes?("--no-color") || !Colorize.default_enabled?(STDOUT, STDERR)
     Crystal.error msg, @color, exit_code: exit_code
   end