Make psql redisplay the query buffer after \e.

Up to now, whatever you'd edited was put back into the query buffer
but not redisplayed, which is less than user-friendly.  But we can
improve that just by printing the text along with a prompt, if we
enforce that the editing result ends with a newline (which it
typically would anyway).  You then continue typing more lines if
you want, or you can type ";" or do \g or \r or another \e.

This is intentionally divorced from readline's processing,
for simplicity and so that it works the same with or without
readline enabled.  We discussed possibly integrating things
more closely with readline; but that seems difficult, uncertainly
portable across different readline and libedit versions, and
of limited real benefit anyway.  Let's try the simple way and
see if it's good enough.

Patch by me, thanks to Fabien Coelho and Laurenz Albe for review

Discussion: https://postgr.es/m/13192.1572318028@sss.pgh.pa.us

1 files changed, 20 insertions, 0 deletions

diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index b3a840756af..f7b1b94599d 100644
--- a/src/bin/psql/mainloop.c
+++ b/src/bin/psql/mainloop.c
@@ -47,6 +47,7 @@ MainLoop(FILE *source)
 	volatile int successResult = EXIT_SUCCESS;
 	volatile backslashResult slashCmdStatus = PSQL_CMD_UNKNOWN;
 	volatile promptStatus_t prompt_status = PROMPT_READY;
+	volatile bool need_redisplay = false;
 	volatile int count_eof = 0;
 	volatile bool die_on_error = false;
 	FILE	   *prev_cmd_source;
@@ -118,6 +119,7 @@ MainLoop(FILE *source)
 			count_eof = 0;
 			slashCmdStatus = PSQL_CMD_UNKNOWN;
 			prompt_status = PROMPT_READY;
+			need_redisplay = false;
 			pset.stmt_lineno = 1;
 			cancel_pressed = false;
 
@@ -152,6 +154,18 @@ MainLoop(FILE *source)
 			/* May need to reset prompt, eg after \r command */
 			if (query_buf->len == 0)
 				prompt_status = PROMPT_READY;
+			/* If query buffer came from \e, redisplay it with a prompt */
+			if (need_redisplay)
+			{
+				if (query_buf->len > 0)
+				{
+					fputs(get_prompt(PROMPT_READY, cond_stack), stdout);
+					fputs(query_buf->data, stdout);
+					fflush(stdout);
+				}
+				need_redisplay = false;
+			}
+			/* Now we can fetch a line */
 			line = gets_interactive(get_prompt(prompt_status, cond_stack),
 									query_buf);
 		}
@@ -518,6 +532,10 @@ MainLoop(FILE *source)
 				{
 					/* should not see this in inactive branch */
 					Assert(conditional_active(cond_stack));
+					/* ensure what came back from editing ends in a newline */
+					if (query_buf->len > 0 &&
+						query_buf->data[query_buf->len - 1] != '\n')
+						appendPQExpBufferChar(query_buf, '\n');
 					/* rescan query_buf as new input */
 					psql_scan_finish(scan_state);
 					free(line);
@@ -529,6 +547,8 @@ MainLoop(FILE *source)
 									pset.encoding, standard_strings());
 					line_saved_in_history = false;
 					prompt_status = PROMPT_READY;
+					/* we'll want to redisplay after parsing what we have */
+					need_redisplay = true;
 				}
 				else if (slashCmdStatus == PSQL_CMD_TERMINATE)
 					break;