Fix empty user in connection string defaulting to OS user

pgconn/config.go

@@ -491,7 +491,9 @@ func parseURLSettings(connString string) (map[string]string, error) {
 	}
 
 	if parsedURL.User != nil {
-		settings["user"] = parsedURL.User.Username()
+		if u := parsedURL.User.Username(); u != "" {
+			settings["user"] = u
+		}
 		if password, present := parsedURL.User.Password(); present {
 			settings["password"] = password
 		}
@@ -618,6 +620,9 @@ func parseKeywordValueSettings(s string) (map[string]string, error) {
 			return nil, errors.New("invalid keyword/value")
 		}
 
+		if key == "user" && val == "" {
+			continue
+		}
 		settings[key] = val
 	}
 

pgconn/config_test.go

@@ -1145,3 +1145,56 @@ application_name = spaced string
 		assertConfigsEqual(t, tt.config, config, fmt.Sprintf("Test %d (%s)", i, tt.name))
 	}
 }
+
+func TestParseConfigExplicitEmptyUserDefaultsToOSUser(t *testing.T) {
+	skipOnWindows(t)
+	clearPgEnvvars(t)
+
+	currentUser, err := user.Current()
+	if err != nil {
+		t.Skip("cannot determine current OS user")
+	}
+
+	tests := []struct {
+		name       string
+		connString string
+		expected   string
+	}{
+		{
+			name:       "keyword value explicit empty user",
+			connString: "host=localhost dbname=test user=",
+			expected:   currentUser.Username,
+		},
+		{
+			name:       "keyword value quoted empty user",
+			connString: "host=localhost dbname=test user=''",
+			expected:   currentUser.Username,
+		},
+		{
+			name:       "url explicit empty user without password",
+			connString: "postgres://@localhost/test",
+			expected:   currentUser.Username,
+		},
+		{
+			name:       "url explicit empty user with password",
+			connString: "postgres://:secret@localhost/test",
+			expected:   currentUser.Username,
+		},
+	}
+
+	for i, tt := range tests {
+		config, err := pgconn.ParseConfig(tt.connString)
+		if !assert.NoErrorf(t, err, "Test %d (%s)", i, tt.name) {
+			continue
+		}
+
+		assert.Equalf(
+			t,
+			tt.expected,
+			config.User,
+			"Test %d (%s): unexpected user",
+			i,
+			tt.name,
+		)
+	}
+}