colors: Disable hyperlinks on dumb terminals.

Before this change, Emacs was being handled as a special case.  By relying on
the TERM variable, Emacs is covered in addition to other terminals which do
not support color.  Additionally this change offers some more granularity to
Emacs as certain setup can support hyperlinks, in those cases the users are
able to enable them by adjusting the TERM variable in their Emacs processes.

* guix/colors.scm: (supports-hyperlinks?): Remove hyperlinks for dumb
terminals instead of any Emacs process.
(dumb-terminal?): New procedure.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>
Merges: #9524

1 files changed, 16 insertions, 3 deletions

diff --git a/guix/colors.scm b/guix/colors.scm
index 543f4c3ec50..6603642d249 100644
--- a/guix/colors.scm
+++ b/guix/colors.scm
@@ -137,6 +137,13 @@ that subsequent output will not have any colors in effect."
     "Return true if PORT is a tty.  Memoize the result."
     (isatty? port)))
 
+(define dumb-terminal?
+  (mlambdaq ()
+    "Return #t if TERM=dumb or if TERM is not set.  Memoize the result."
+    (match (getenv "TERM")
+      ((or "dumb" #f) #t)
+      (_ #f))))
+
 (define (color-output? port)
   "Return true if we should write colored output to PORT."
   (and (not (getenv "NO_COLOR"))
@@ -236,10 +243,16 @@ documented at
   "Return true if PORT is a terminal that supports hyperlink escapes."
   ;; Note that terminals are supposed to ignore OSC escapes they don't
   ;; understand (this is the case of xterm as of version 349, for instance.)
-  ;; However, Emacs comint as of 26.3 does not ignore it and instead lets it
-  ;; through, hence the 'INSIDE_EMACS' special case below.
+  ;;
+  ;; Emacs users can add 'ansi-osc-compilation-filter' to
+  ;; 'compilation-filter-hook' to propertize the hyperlinks, in that case,
+  ;; remember to set TERM to something other than the default.  For example, a
+  ;; user of 'M-x shell' that is using Bash, may create a
+  ;; '~/.emacs.d/init_bash.sh' file with 'export TERM=eterm-color'.  For the
+  ;; compilation filters to affect 'M-x shell', one can enable
+  ;; 'compilation-shell-minor-mode'.
   (and (isatty?* port)
-       (not (getenv "INSIDE_EMACS"))))
+       (not (dumb-terminal?))))
 
 (define* (file-hyperlink file #:optional (text file))
   "Return TEXT with escapes for a hyperlink to FILE."