lib: init ansi module

The lib.ansi module provides a basic set of ANSI escape sequences to
colorize and style text. The main purpose is to colorize trace
messages (warnings, errors).

lib/ansi.nix

@@ -0,0 +1,58 @@
+# This exports a basic set of ANSI escape sequences to colorize terminal output.
+
+{ ... }:
+
+let
+ colorCodeMap = {
+ black = 0;
+ red = 1;
+ green = 2;
+ yellow = 3;
+ blue = 4;
+ magenta = 5;
+ cyan = 6;
+ white = 7;
+ };
+
+ # Escape character. "\e" or similar encodings currently not supported by Nix.
+ esc = "";
+ reset = "${esc}[0m";
+ style = {
+ bold = "${esc}[1m";
+ italic = "${esc}[3m";
+ };
+ # Only foreground colors are supported at the moment.
+ color = builtins.mapAttrs (name: value: "${esc}[3${toString value}m") colorCodeMap;
+
+ /* Stylizes a string with ANSI escape sequences.
+
+ Type: stylize :: [String] -> String -> String
+ */
+ stylize =
+ # List of ANSI style attributes.
+ styles:
+ # Text to encapsulate by style.
+ text:
+ let
+ ansiBefore = builtins.concatStringsSep "" styles;
+ in
+ if text == ""
+ then ""
+ else "${ansiBefore}${text}${reset}";
+
+ /* Stylizes a string as bold and red.
+
+ Type: stylizeError :: String -> String
+ */
+ stylizeError = text: stylize [ style.bold color.red ] text;
+
+ /* Stylizes a string as bold and yellow.
+
+ Type: stylizeWarn :: String -> String
+ */
+ stylizeWarn = text: stylize [ style.bold color.yellow ] text;
+in
+{
+ inherit color style reset;
+ inherit stylize stylizeError stylizeWarn;
+}

lib/default.nix

@@ -45,6 +45,7 @@ let
  generators = callLibs ./generators.nix;
 
  # misc
+ ansi = callLibs ./ansi.nix;
  asserts = callLibs ./asserts.nix;
  debug = callLibs ./debug.nix;
  misc = callLibs ./deprecated.nix;

lib/tests/misc.nix

@@ -20,6 +20,7 @@ let
  inherit (lib)
  allUnique
  and
+ ansi
  attrNames
  attrsets
  attrsToList
@@ -1543,6 +1544,21 @@ runTests {
  }'';
  };
 
+# MISC
+
+ testAnsiStylizeEmptyInput = {
+ expr = ansi.stylize [ansi.style.bold ansi.color.fg.red] "";
+ expected = "";
+ };
+ testAnsiStylizeError = {
+ expr = ansi.stylizeError "ERROR";
+ expected = "ERROR";
+ };
+ testAnsiStylizeWarn = {
+ expr = ansi.stylizeWarn "WARN";
+ expected = "WARN";
+ };
+
 # CLI
 
  testToGNUCommandLine = {