psql: give ^D hint for \q in place where \q is ignored

Also add comment on why exit/quit are not documented.

Discussion: https://postgr.es/m/20180202053928.GA13472@momjian.us

diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index a3ef15058fcb66c3968c3e6f3a77632dbef2d6fd..c06ce3ca09cd028cdbe2fb2f32ce93a8df01a530 100644 (file)
--- a/src/bin/psql/mainloop.c
+++ b/src/bin/psql/mainloop.c
@@ -223,6 +223,7 @@ MainLoop(FILE *source)
                        char       *rest_of_line = NULL;
                        bool            found_help = false;
                        bool            found_exit_or_quit = false;
+                       bool            found_q = false;
 
                        /* Search for the words we recognize;  must be first word */
                        if (pg_strncasecmp(first_word, "help", 4) == 0)
@@ -237,10 +238,18 @@ MainLoop(FILE *source)
                                found_exit_or_quit = true;
                        }
 
+                       else if (strncmp(first_word, "\\q", 2) == 0)
+                       {
+                               rest_of_line = first_word + 2;
+                               found_q = true;
+                       }
+
                        /*
                         * If we found a command word, check whether the rest of the line
                         * contains only whitespace plus maybe one semicolon.  If not,
-                        * ignore the command word after all.
+                        * ignore the command word after all.  These commands are only
+                        * for compatibility with other SQL clients and are not
+                        * documented.
                         */
                        if (rest_of_line != NULL)
                        {
@@ -288,6 +297,7 @@ MainLoop(FILE *source)
                                        continue;
                                }
                        }
+
                        /*
                         * "quit" and "exit" are only commands when the query buffer is
                         * empty, but we emit a one-line message even when it isn't to
@@ -318,6 +328,21 @@ MainLoop(FILE *source)
                                        break;
                                }
                        }
+
+                       /*
+                        * If they typed "\q" in a place where "\q" is not active,
+                        * supply a hint.  The text is still added to the query
+                        * buffer.
+                        */
+                       if (found_q && query_buf->len != 0 &&
+                               prompt_status != PROMPT_READY &&
+                               prompt_status != PROMPT_CONTINUE &&
+                               prompt_status != PROMPT_PAREN)
+#ifndef WIN32
+                                       puts(_("Use control-D to quit."));
+#else
+                                       puts(_("Use control-C to quit."));
+#endif
                }
 
                /* echo back if flag is set, unless interactive */