Allow variables to be used as part of a value in configuration.

Signed-off-by: Joseph Riddle <[email protected]>

Author: joeriddles

conf/parse.go

@@ -31,6 +31,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strconv"
 	"strings"
 	"time"
@@ -287,6 +288,7 @@ func (p *parser) processItem(it item, fp string) error {
 		setValue(it, p.popContext())
 	case itemString:
 		// FIXME(dlc) sanitize string?
+		p.checkForEmbeddedVariables(&it)
 		setValue(it, it.val)
 	case itemInteger:
 		lastDigit := 0
@@ -430,6 +432,33 @@ const pkey = "pk"
 // We special case raw strings here that are bcrypt'd. This allows us not to force quoting the strings
 const bcryptPrefix = "2a$"
 
+// To match embedded variables.
+var varPat = regexp.MustCompile(`\$\$[^@\s]+`)
+
+// checkForEmbeddedVariable will check for embedded variables in an itemString.
+// If they are found and we can look them up we will replace them in item, otherwise will error.
+func (p *parser) checkForEmbeddedVariables(it *item) error {
+	if !strings.ContainsAny(it.val, "$$") {
+		return nil
+	}
+	// We have some embedded variables.
+	for _, m := range varPat.FindAllString(it.val, -1) {
+		value, found, err := p.lookupVariable(m[2:]) // Strip leading $$ for lookup.
+		if err != nil {
+			return fmt.Errorf("variable reference for '%s' on line %d could not be parsed: %s",
+				m, it.line, err)
+		}
+		if !found {
+			return fmt.Errorf("variable reference for '%s' on line %d can not be found",
+				m, it.line)
+		}
+		if v, ok := value.(string); ok {
+			it.val = strings.Replace(it.val, m, v, 1)
+		}
+	}
+	return nil
+}
+
 // lookupVariable will lookup a variable reference. It will use block scoping on keys
 // it has seen before, with the top level scoping being the environment variables. We
 // ignore array contexts and only process the map contexts..

conf/parse_test.go

@@ -166,6 +166,82 @@ func TestEnvVariableStringStartingWithNumberUsingQuotes(t *testing.T) {
 	test(t, fmt.Sprintf("foo = $%s", evar), ex)
 }
 
+func TestEnvVariableEmbedded(t *testing.T) {
+	cluster := `
+		cluster {
+			# set the variable token
+			TOKEN: abc
+			authorization {
+				user: user
+				# normal variable syntax
+				password: $TOKEN
+			}
+			# embedded variable syntax
+			routes = [ nats://user:[email protected]:6222 ]
+		}`
+	ex := map[string]any{
+		"cluster": map[string]any{
+			"TOKEN": "abc",
+			"authorization": map[string]any{
+				"user":     "user",
+				"password": "abc",
+			},
+			"routes": []any{
+				"nats://user:[email protected]:6222",
+			},
+		},
+	}
+
+	// don't use test() here because we want to test the Parse function without checking pedantic mode.
+	m, err := Parse(cluster)
+	if err != nil {
+		t.Fatalf("Received err: %v\n", err)
+	}
+	if m == nil {
+		t.Fatal("Received nil map")
+	}
+
+	if !reflect.DeepEqual(m, ex) {
+		t.Fatalf("Not Equal:\nReceived: '%+v'\nExpected: '%+v'\n", m, ex)
+	}
+}
+
+func TestEnvVariableEmbeddedMissing(t *testing.T) {
+	cluster := `
+		cluster {
+			authorization {
+				user: user
+				# normal variable syntax
+				password: $TOKEN
+			}
+			# embedded variable syntax
+			routes = [ nats://user:[email protected]:6222 ]
+		}`
+
+	_, err := Parse(cluster)
+	if err == nil {
+		t.Fatalf("Expected err not being able to process embedded variable, got none")
+	}
+}
+
+func TestEnvVariableEmbeddedOutsideOfQuotes(t *testing.T) {
+	cluster := `
+		cluster {
+			authorization {
+				user: user
+				# invalid embedded variable syntax
+				password: $$TOKEN
+			}
+			# embedded variable syntax
+			routes = [ nats://user:[email protected]:6222 ]
+		}`
+
+	_, err := Parse(cluster)
+	if err == nil {
+		t.Fatalf("Expected err not being able to process embedded variable, got none")
+	}
+}
+
 func TestBcryptVariable(t *testing.T) {
 	ex := map[string]any{
 		"password": "$2a$11$ooo",