fix: Recover PS1 before command execution.

Before this change, when doing completion in the same process PS1 was
modified to be able to detect the end of the completion command output
and it was recovered later on from PROMPT_COMMAND, just *after*
executing the user command, before building the next prompt.

The effect was not visible, unless the user command included $PS1, so if
you did:

> echo $PS1

and ran completion while editing that command, the PS1 that would be
output would be the one from bash-completion.

This change switches to another approach for recovering the prompt that
allows recovering it before executing the user command: a DEBUG trap is
registered which restores PS1 and PROMPT_COMMAND if the previous command
included __ebrcet. This change also adds __ebcret after the last command
issued by completion.

This way, the last command issued by completion uses the fake prompt,
but the command run just after that sees the real prompt in its
variable.

issue #77

Author: szermatt

bash-completion.el

@@ -1533,7 +1533,7 @@ Return the status code of the command, as a number."
             ((not define-functions)
              (concat
               "if type __ebcpre &>/dev/null; then "
-              "  __ebcpre; %s; "
+              "  __ebcpre; %s; __ebcret $?; "
               "else "
               "  echo ==emacs==nopre=${BASH_VERSION}==.; "
               "  __ebcp=(\"$PS1\" \"$PROMPT_COMMAND\");"
@@ -1548,28 +1548,26 @@ Return the status code of the command, as a number."
                "    c=$((c+1));"
                "  fi;"
                "  history -d $c &>/dev/null || true;"
-               "}; function __ebcpre {"
+               "} ; function __ebcret {"
+               "  __ebcret=t;"
+               "  return $1;"
+               "} ; function __ebctrap {"
+               " if [[ \"$__ebcret\" = \"t\" && ${#__ebcp[@]} -gt 0 ]]; then"
+               "  PS1=\"${__ebcp[0]}\";"
+               "  PROMPT_COMMAND=\"${__ebcp[1]}\";"
+               "  unset __ebcp;"
+               "  unset __ebcret;"
+               " fi;"
+               "} ; trap __ebctrap DEBUG ; function __ebcpre {"
                "  set +x; set +o emacs; set +o vi;"
                "  echo \"==emacs==bash=${BASH_VERSION}==.\";"
                "  if [[ ${#__ebcp[@]} = 0 ]]; then "
                "    __ebcp=(\"$PS1\" \"$PROMPT_COMMAND\");"
                "  fi;"
-               "  PROMPT_COMMAND=" ;; set a temporary prompt
-               (bash-completion-quote
-                (concat "PS1=" bash-completion--ps1 ";"
-                        "PROMPT_COMMAND=" ;; recover prompt
-                        (bash-completion-quote
-                         (concat
-                          "__ebcr=$?;"
-                          "PS1=\"${__ebcp[0]}\";"
-                          "PROMPT_COMMAND=\"${__ebcp[1]}\";"
-                          "unset __ebcp;"
-                          "if [[ -n \"$PROMPT_COMMAND\" ]]; then"
-                          "  (exit $__ebcr); eval \"$PROMPT_COMMAND\";"
-                          "fi;"))))
-               ";"
+               "  PS1=" bash-completion--ps1 ";"
+               "  unset PROMPT_COMMAND;"
                "  __ebcnohistory 1;"
-               "} && { __ebcpre; %s; }\n")))
+               "} ; { __ebcpre; %s; __ebcret $?; }\n")))
            commandline)))
     (setq bash-completion--debug-info
           (list (cons 'commandline complete-command)
@@ -1591,7 +1589,7 @@ Return the status code of the command, as a number."
           ;; common initialization, then retry.
           (bash-completion-send "__ebcnohistory" process timeout debug-context 'define-functions)
           (bash-completion--setup-bash-common process)
-          (funcall send-string process (concat "__ebcpre; " commandline ";\n"))
+          (funcall send-string process (concat "__ebcpre; " commandline "; __ebcret $?\n"))
           (bash-completion--wait-for-regexp
            "short-timeout" process "==emacs==bash=[0-9].*?==."
            bash-completion-short-command-timeout))

test/bash-completion-integration-test.el

@@ -900,4 +900,30 @@ $ ")))))
             "dummy moretestfile "
             (bash-completion_test-complete "dummy moret")))))
 
+(ert-deftest bash-completion-integration-recover-status-ps1 ()
+  (bash-completion_test-with-shell-harness
+   (concat ; .bashrc
+    "function dummy { echo --$PS1--; }\n"
+    "function _dummy {\n"
+    "    COMPREPLY=( dummy )\n"
+    "}\n"
+    "complete -F _dummy dummy\n"
+    "PS1='$ '")
+   nil
+   ;; The first time initializes completion, the second time executes
+   ;; an already initialized completion. The two cases behave very
+   ;; differently, so we test both.
+   (dotimes (i 2)
+     (should (equal
+              "dummy dummy "
+              (bash-completion_test-complete "dummy dum")))
+     (let ((start (line-beginning-position)))
+       (comint-send-input)
+       (bash-completion_test-wait-for-prompt start)))
+
+   ;; The PS1 printed by the dummy function should be the one set in
+   ;; the init section, and not the one set by bash completion.
+   (should (equal (bash-completion_test-buffer-string)
+                  "$ dummy dummy\n--$ --\n$ dummy dummy\n--$ --\n$ "))))
+
 ;;; bash-completion-integration-test.el ends here