config: make parsing configurations without usable values invalid

This makes configuration files that are empty, or read and processed
by the parser but with no detected values now return an error.

Signed-off-by: Waldemar Quevedo <wally@nats.io>

conf/parse.go

@@ -146,7 +146,9 @@ func parse(data, fp string, pedantic bool) (p *parser, err error) {
 			return nil, err
 		}
 	}
-
+	if len(p.mapping) == 0 {
+		return nil, fmt.Errorf("config has no values or is empty")
+	}
 	return p, nil
 }
 

conf/parse_test.go

@@ -403,3 +403,30 @@ func TestParserNoInfiniteLoop(t *testing.T) {
 		}
 	}
 }
+
+func TestParseWithNoValues(t *testing.T) {
+	for _, test := range []string{
+		``,
+		`aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		`              aaaaaaaaaaaaaaaaaaaaaaaaaaa`,
+		`     aaaaaaaaaaaaaaaaaaaaaaaaaaa         `,
+		`
+                # just comments with no values
+                # is also invalid.
+                `,
+		`
+                # with comments and no spaces to create key values
+                # is also an invalid config.
+                aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
+                `,
+		`
+                a,a,a,a,a,a,a,a,a,a,a
+                `,
+	} {
+		if _, err := parse(test, "", true); err == nil {
+			t.Fatal("expected an error")
+		} else if !strings.Contains(err.Error(), "config has no values or is empty") {
+			t.Fatal("expected invalid conf error")
+		}
+	}
+}