profile/systemd-osc-context: fix overriding of PROMPT_COMMAND

In https://github.com/systemd/systemd/issues/39114 users are reporting
that our script overrides PROMPT_COMMAND that they had. After looking
at /etc/bashrc in Fedora, I see that it only sets PROMPT_COMMAND if
[ -z "$PROMPT_COMMAND" ]. Let's adjust the script so this continues to
work.

Fixes https://github.com/systemd/systemd/issues/39114.
(This is a bit of a stretch. 39114 was originally about SecureCRT,
but that was resolved in SecureCRT. But there was a lot of dicussion
about the prompt being overriden, which this commit should fix.)

diff --git a/profile.d/80-systemd-osc-context.sh b/profile.d/80-systemd-osc-context.sh
index a7392eedba20570ce03ee4fbe70431b30de6120e..60ab9904f1d3207c520d647cd6000a70a56ed159 100644 (file)
--- a/profile.d/80-systemd-osc-context.sh
+++ b/profile.d/80-systemd-osc-context.sh
@@ -57,7 +57,11 @@ __systemd_osc_context_precmdline() {
 }
 
 if [[ -n "${BASH_VERSION:-}" ]] && [[ "${TERM:-}" != "dumb" ]]; then
-    # Whenever a new prompt is shown close the previous command, and prepare new command
+    # Legacy bashrc will assign PROMPT_COMMAND=, which is equivalent to assigning
+    # index 0 in the array. Leave an empty spot to handle this gracefully.
+    [ -n "$(declare -p PROMPT_COMMAND 2>/dev/null)" ] || PROMPT_COMMAND+=('')
+
+    # Whenever a new prompt is shown, close the previous command, and prepare new command
     PROMPT_COMMAND+=(__systemd_osc_context_precmdline)
 
     # PS0 is shown right after a prompt completed, but before the command is executed