Make psql's "\pset format" command reject non-unique abbreviations.

The previous behavior of preferring the oldest match had the advantage
of not breaking existing scripts when we add a conflicting format name;
but that behavior was undocumented and fragile (it seems just luck that
commit add9182e5 didn't break it).  Let's go over to the less mistake-
prone approach of complaining when there are multiple matches.

Since this is a small compatibility break, no back-.

Daniel Vérité

Discussion: https://postgr.es/m/cb7e1caf-3ea6-450d-af28-f524903a030c@manitou-mail.org

diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 0dea54d3ce07e166bd9df2aaa2848a06747fd9cb..04e227b5a6478a5d0031bbd5558964207a9352a6 100644 (file)
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -3637,28 +3637,51 @@ do_pset(const char *param, const char *value, printQueryOpt *popt, bool quiet)
    /* set format */
    if (strcmp(param, "format") == 0)
    {
+       static const struct fmt
+       {
+           const char *name;
+           enum printFormat number;
+       }           formats[] =
+       {
+           /* remember to update error message below when adding more */
+           {"aligned", PRINT_ALIGNED},
+           {"asciidoc", PRINT_ASCIIDOC},
+           {"html", PRINT_HTML},
+           {"latex", PRINT_LATEX},
+           {"latex-longtable", PRINT_LATEX_LONGTABLE},
+           {"troff-ms", PRINT_TROFF_MS},
+           {"unaligned", PRINT_UNALIGNED},
+           {"wrapped", PRINT_WRAPPED}
+       };
+
        if (!value)
            ;
-       else if (pg_strncasecmp("aligned", value, vallen) == 0)
-           popt->topt.format = PRINT_ALIGNED;
-       else if (pg_strncasecmp("asciidoc", value, vallen) == 0)
-           popt->topt.format = PRINT_ASCIIDOC;
-       else if (pg_strncasecmp("html", value, vallen) == 0)
-           popt->topt.format = PRINT_HTML;
-       else if (pg_strncasecmp("latex", value, vallen) == 0)
-           popt->topt.format = PRINT_LATEX;
-       else if (pg_strncasecmp("latex-longtable", value, vallen) == 0)
-           popt->topt.format = PRINT_LATEX_LONGTABLE;
-       else if (pg_strncasecmp("troff-ms", value, vallen) == 0)
-           popt->topt.format = PRINT_TROFF_MS;
-       else if (pg_strncasecmp("unaligned", value, vallen) == 0)
-           popt->topt.format = PRINT_UNALIGNED;
-       else if (pg_strncasecmp("wrapped", value, vallen) == 0)
-           popt->topt.format = PRINT_WRAPPED;
        else
        {
-           psql_error("\\pset: allowed formats are aligned, asciidoc, html, latex, latex-longtable, troff-ms, unaligned, wrapped\n");
-           return false;
+           int         match_pos = -1;
+
+           for (int i = 0; i < lengthof(formats); i++)
+           {
+               if (pg_strncasecmp(formats[i].name, value, vallen) == 0)
+               {
+                   if (match_pos < 0)
+                       match_pos = i;
+                   else
+                   {
+                       psql_error("\\pset: ambiguous abbreviation \"%s\" matches both \"%s\" and \"%s\"\n",
+                                  value,
+                                  formats[match_pos].name, formats[i].name);
+                       return false;
+                   }
+               }
+           }
+           if (match_pos < 0)
+           {
+               psql_error("\\pset: allowed formats are aligned, asciidoc, html, latex, latex-longtable, troff-ms, unaligned, wrapped\n");
+               return false;
+           }
+           else
+               popt->topt.format = formats[match_pos].number;
        }
    }