Fix change to default colors in job log

changelogs/unreleased/fix-job-log-default-colors.yml

+---
+title: Fix change to default foreground and backgorund colors in job log
+merge_request: 20787
+author:
+type: fixed

lib/gitlab/ci/ansi2json/parser.rb

@@ -94,7 +94,7 @@ module Gitlab
 
         def on_38(stack) { fg: fg_color_256(stack) } end
 
-        def on_39(_) { fg: fg_color(9) } end
+        def on_39(_) { fg: nil } end
 
         def on_40(_) { bg: bg_color(0) } end
 
@@ -114,8 +114,7 @@ module Gitlab
 
         def on_48(stack) { bg: bg_color_256(stack) } end
 
-        # TODO: all the x9 never get called?
-        def on_49(_) { fg: fg_color(9) } end
+        def on_49(_) { bg: nil } end
 
         def on_90(_) { fg: fg_color(0, 'l') } end
 

lib/gitlab/ci/ansi2json/style.rb

@@ -61,9 +61,9 @@ module Gitlab
           case
           when changes[:reset]
             reset!
-          when changes[:fg]
+          when changes.key?(:fg)
             @fg = changes[:fg]
-          when changes[:bg]
+          when changes.key?(:bg)
             @bg = changes[:bg]
           when changes[:enable]
             @mask |= changes[:enable]

spec/lib/gitlab/ci/ansi2json/style_spec.rb

@@ -147,6 +147,10 @@ describe Gitlab::Ci::Ansi2json::Style do
         [%w[1], %w[0], '', 'resets style from format bold'],
         [%w[1 3], %w[0], '', 'resets style from format bold and italic'],
         [%w[1 3 term-fg-l-red term-bg-yellow], %w[0], '', 'resets all formats and colors'],
+        # default foreground
+        [%w[31 42], %w[39], 'term-bg-green', 'set foreground from red to default leaving background unchanged'],
+        # default background
+        [%w[31 42], %w[49], 'term-fg-red', 'set background from green to default leaving foreground unchanged'],
         # misc
         [[], %w[1 30 42 3], 'term-fg-l-black term-bg-green term-bold term-italic', 'adds fg color, bg color and formats from no style'],
         [%w[3 31], %w[23 1 43], 'term-fg-l-red term-bg-yellow term-bold', 'replaces format italic with bold and adds a yellow background']