Allow invisible PROMPT2 in psql.

Keep track of the visible width of PROMPT1, and provide %w as a way
for PROMPT2 to generate the same number of spaces.

Author: Thomas Munro, with ideas from others
Reviewed-by: Tom Lane (earlier version)
Discussion: https://postgr.es/m/CA%2BhUKG%2BzGd7RigjWbxwhzGW59gUpf76ydQECeGdEdodH6nd__A%40mail.gmail.com

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 7789fc6177699618bc256f21bffe3e529b12f086..a55ca6a2666fda5a7667ff51db21c06f62f89d5a 100644 (file)
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -4310,6 +4310,18 @@ testdb=> \set PROMPT1 '%[%033[1;33;40m%]%n@%/%R%[%033[0m%]%# '
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><literal>%w</literal></term>
+        <listitem>
+        <para>
+        Whitespace of the same width as the most recent output of
+        <varname>PROMPT1</varname>.  This can be used as a
+        <varname>PROMPT2</varname> setting, so that multi-line statements are
+        aligned with the first line, but there is no visible secondary prompt.
+        </para>
+        </listitem>
+      </varlistentry>
+
     </variablelist>
 
     To insert a percent sign into your prompt, write

diff --git a/src/bin/psql/prompt.c b/src/bin/psql/prompt.c
index 195192a95d611b19711d878e9b6d29e61811abb2..41c6f21ecfce421340438bf033bb56f7e4157765 100644 (file)
--- a/src/bin/psql/prompt.c
+++ b/src/bin/psql/prompt.c
@@ -39,6 +39,7 @@
  * %n - database user name
  * %/ - current database
  * %~ - like %/ but "~" when database name equals user name
+ * %w - whitespace of the same width as the most recent output of PROMPT1
  * %# - "#" if superuser, ">" otherwise
  * %R - in prompt1 normally =, or ^ if single line mode,
  *         or a ! if session is not connected to a database;
@@ -74,6 +75,7 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
    bool        esc = false;
    const char *p;
    const char *prompt_string = "? ";
+   static size_t last_prompt1_width = 0;
 
    switch (status)
    {
@@ -124,6 +126,13 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
                    }
                    break;
 
+                   /* Whitespace of the same width as the last PROMPT1 */
+               case 'w':
+                   if (pset.db)
+                       memset(buf, ' ',
+                              Min(last_prompt1_width, sizeof(buf) - 1));
+                   break;
+
                    /* DB server hostname (long/short) */
                case 'M':
                case 'm':
@@ -336,5 +345,48 @@ get_prompt(promptStatus_t status, ConditionalStack cstack)
            strlcat(destination, buf, sizeof(destination));
    }
 
+   /* Compute the visible width of PROMPT1, for PROMPT2's %w */
+   if (prompt_string == pset.prompt1)
+   {
+       char       *p = destination;
+       char       *end = p + strlen(p);
+       bool        visible = true;
+
+       last_prompt1_width = 0;
+       while (*p)
+       {
+#if defined(USE_READLINE) && defined(RL_PROMPT_START_IGNORE)
+           if (*p == RL_PROMPT_START_IGNORE)
+           {
+               visible = false;
+               ++p;
+           }
+           else if (*p == RL_PROMPT_END_IGNORE)
+           {
+               visible = true;
+               ++p;
+           }
+           else
+#endif
+           {
+               int         chlen,
+                           chwidth;
+
+               chlen = PQmblen(p, pset.encoding);
+               if (p + chlen > end)
+                   break;      /* Invalid string */
+
+               if (visible)
+               {
+                   chwidth = PQdsplen(p, pset.encoding);
+                   if (chwidth > 0)
+                       last_prompt1_width += chwidth;
+               }
+
+               p += chlen;
+           }
+       }
+   }
+
    return destination;
 }