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-patch.

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;
                }
        }