bash: Mark shell sessions as active on command start

Previously shell sessions were considered inactive until the first
interactive command has exited. This caused false positives when long
running first command was killed because shell session was considered
inactive.

Now shell session is considered active when the first interactive
command is started. The code is somewhat ugly because it includes
workaround for known bugs.

Author: sio

dotfiles/bash/bashrc.copy

@@ -1,5 +1,9 @@
 # BASH CONFIGURATION FILE
 
+# Source this file only once (most useful when linked to from ~/.profile and ~/.bash_profile)
+if [[ -n "$COMMON_LOADED" ]]; then return; fi
+COMMON_LOADED=yes
+
 # Load configuration from Git repo
 COMMON="$HOME/.common"
 . "$COMMON/dotfiles/bash/bashrc"

dotfiles/bash/interactive

@@ -31,14 +31,27 @@ shopt -s globstar
 # Exit interactive sessions that were never used (forgotten tmux panes,
 # VSCode terminals, etc).
 # If shell session was used for at least one command TMOUT will be disabled.
-TMOUT_EXIT_FORGOTTEN_SHELL="${TMOUT_EXIT_FORGOTTEN_SHELL:-900}" # 15 minutes
-TMOUT="$TMOUT_EXIT_FORGOTTEN_SHELL"
-_exit_forgotten_shell() {
-    if [[ -n "$_INTERACTIVE_COMMANDS_ENTERED" ]]
-    then
-        return
-    fi
-    _INTERACTIVE_COMMANDS_ENTERED=some
-    TMOUT=0
-}
-PROMPT_COMMAND="_exit_forgotten_shell; $PROMPT_COMMAND"
+TMOUT_FORGOTTEN_SHELL="${TMOUT_FORGOTTEN_SHELL:-900}" # 15 minutes
+if [[ "$TMOUT_FORGOTTEN_SHELL" -gt 0 ]]
+then
+    TMOUT="$TMOUT_FORGOTTEN_SHELL"
+    unset TMOUT_FORGOTTEN_SHELL
+
+    PROMPT_COMMAND_FORGOTTEN_SHELL="$PROMPT_COMMAND"
+    _reset_forgotten_shell_detection() {
+        if [[ -v PROMPT_COMMAND_FORGOTTEN_SHELL ]]
+        then
+            PROMPT_COMMAND="$PROMPT_COMMAND_FORGOTTEN_SHELL"
+            unset PROMPT_COMMAND_FORGOTTEN_SHELL
+        fi
+        unset -f _reset_forgotten_shell_detection
+        unset -f _this_shell_is_not_forgotten
+    }
+
+    _this_shell_is_not_forgotten() {
+        TMOUT=0
+        PROMPT_COMMAND="trap - DEBUG; _reset_forgotten_shell_detection; $PROMPT_COMMAND_FORGOTTEN_SHELL"
+        trap - DEBUG # trap does not really untrap from trap, hence the delegation to PROMPT_COMMAND above
+    }
+    PROMPT_COMMAND="trap _this_shell_is_not_forgotten DEBUG; $PROMPT_COMMAND"
+fi