psql: fix \connect with URIs and conninfo strings

psql was already accepting conninfo strings as the first parameter in
\connect, but the way it worked wasn't sane; some of the other
parameters would get the previous connection's values, causing it to
connect to a completely unexpected server or, more likely, not finding
any server at all because of completely wrong combinations of
parameters.

Fix by explicitely checking for a conninfo-looking parameter in the
dbname position; if one is found, use its complete specification rather
than mix with the other arguments.  Also, change tab-completion to not
try to complete conninfo/URI-looking "dbnames" and document that
conninfos are accepted as first argument.

There was a weak consensus to backpatch this, because while the behavior
of using the dbname as a conninfo is nowhere documented for \connect, it
is reasonable to expect that it works because it does work in many other
contexts.  Therefore this is backpatched all the way back to 9.0.

To implement this, routines previously private to libpq have been
duplicated so that psql can decide what looks like a conninfo/URI
string.  In back branches, just duplicate the same code all the way back
to 9.2, where URIs where introduced; 9.0 and 9.1 have a simpler version.
In master, the routines are moved to src/common and renamed.

Author: David Fetter, Andrew Dunstan.  Some editorialization by me
(probably earning a Gierth's "Sloppy" badge in the process.)
Reviewers: Andrew Gierth, Erik Rijkers, Pavel Stěhule, Stephen Frost,
Robert Haas, Andrew Dunstan.

1 files changed, 41 insertions, 0 deletions

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index c08c81366d1..b81a2c21630 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -1748,3 +1748,44 @@ expand_tilde(char **filename)
 
 	return;
 }
+
+/*
+ * Checks if connection string starts with either of the valid URI prefix
+ * designators.
+ *
+ * Returns the URI prefix length, 0 if the string doesn't contain a URI prefix.
+ *
+ * XXX This is a duplicate of the eponymous libpq function.
+ */
+static int
+uri_prefix_length(const char *connstr)
+{
+	/* The connection URI must start with either of the following designators: */
+	static const char uri_designator[] = "postgresql://";
+	static const char short_uri_designator[] = "postgres://";
+
+	if (strncmp(connstr, uri_designator,
+				sizeof(uri_designator) - 1) == 0)
+		return sizeof(uri_designator) - 1;
+
+	if (strncmp(connstr, short_uri_designator,
+				sizeof(short_uri_designator) - 1) == 0)
+		return sizeof(short_uri_designator) - 1;
+
+	return 0;
+}
+
+/*
+ * Recognized connection string either starts with a valid URI prefix or
+ * contains a "=" in it.
+ *
+ * Must be consistent with parse_connection_string: anything for which this
+ * returns true should at least look like it's parseable by that routine.
+ *
+ * XXX This is a duplicate of the eponymous libpq function.
+ */
+bool
+recognized_connection_string(const char *connstr)
+{
+	return uri_prefix_length(connstr) != 0 || strchr(connstr, '=') != NULL;
+}