Fix for case-insensitive header replacements (#476)

middleware/replacer.go

@@ -98,28 +98,20 @@ func NewReplacer(r *http.Request, rr *responseRecorder, emptyValue string) Repla
 // the string with the replaced values.
 func (r replacer) Replace(s string) string {
 	// Header replacements - these are case-insensitive, so we can't just use strings.Replace()
-	startPos := strings.Index(s, headerReplacer)
-	for startPos > -1 {
-		// carefully find end of placeholder
-		endOffset := strings.Index(s[startPos+1:], "}")
-		if endOffset == -1 {
-			startPos = strings.Index(s[startPos+len(headerReplacer):], headerReplacer)
-			continue
-		}
-		endPos := startPos + len(headerReplacer) + endOffset
-
-		// look for replacement, case-insensitive
-		placeholder := strings.ToLower(s[startPos:endPos])
+	for strings.Contains(s, headerReplacer) {
+		idxStart := strings.Index(s, headerReplacer)
+		endOffset := idxStart + len(headerReplacer)
+		idxEnd := strings.Index(s[endOffset:], "}")
+		if idxEnd > -1 {
+			placeholder := strings.ToLower(s[idxStart : endOffset+idxEnd+1])
 			replacement := r.replacements[placeholder]
 			if replacement == "" {
 				replacement = r.emptyValue
 			}
-
-		// do the replacement manually
-		s = s[:startPos] + replacement + s[endPos:]
-
-		// move to next one
-		startPos = strings.Index(s[endOffset:], headerReplacer)
+			s = s[:idxStart] + replacement + s[endOffset+idxEnd+1:]
+		} else {
+			break
+		}
 	}
 
 	// Regular replacements - these are easier because they're case-sensitive

middleware/replacer_test.go

@@ -45,7 +45,8 @@ func TestReplace(t *testing.T) {
 	if err != nil {
 		t.Fatal("Request Formation Failed\n")
 	}
-	request.Header.Set("Custom", "fooBar")
+	request.Header.Set("Custom", "foobarbaz")
+	request.Header.Set("ShorterVal", "1")
 	repl := NewReplacer(request, recordRequest, "-")
 
 	if expected, actual := "This host is localhost.", repl.Replace("This host is {host}."); expected != actual {
@@ -57,12 +58,12 @@ func TestReplace(t *testing.T) {
 	if expected, actual := "The response status is 200.", repl.Replace("The response status is {status}."); expected != actual {
 		t.Errorf("{status} replacement: expected '%s', got '%s'", expected, actual)
 	}
-	if expected, actual := "The Custom header is fooBar.", repl.Replace("The Custom header is {>Custom}."); expected != actual {
+	if expected, actual := "The Custom header is foobarbaz.", repl.Replace("The Custom header is {>Custom}."); expected != actual {
 		t.Errorf("{>Custom} replacement: expected '%s', got '%s'", expected, actual)
 	}
 
 	// Test header case-insensitivity
-	if expected, actual := "The cUsToM header is fooBar...", repl.Replace("The cUsToM header is {>cUsToM}..."); expected != actual {
+	if expected, actual := "The cUsToM header is foobarbaz...", repl.Replace("The cUsToM header is {>cUsToM}..."); expected != actual {
 		t.Errorf("{>cUsToM} replacement: expected '%s', got '%s'", expected, actual)
 	}
 
@@ -80,6 +81,16 @@ func TestReplace(t *testing.T) {
 	if expected, actual := "Bad {>Custom placeholder", repl.Replace("Bad {>Custom placeholder"); expected != actual {
 		t.Errorf("bad header placeholder: expected '%s', got '%s'", expected, actual)
 	}
+
+	// Test bad header placeholder with valid one later
+	if expected, actual := "Bad -", repl.Replace("Bad {>Custom placeholder {>ShorterVal}"); expected != actual {
+		t.Errorf("bad header placeholders: expected '%s', got '%s'", expected, actual)
+	}
+
+	// Test shorter header value with multiple placeholders
+	if expected, actual := "Short value 1 then foobarbaz.", repl.Replace("Short value {>ShorterVal} then {>Custom}."); expected != actual {
+		t.Errorf("short value: expected '%s', got '%s'", expected, actual)
+	}
 }
 
 func TestSet(t *testing.T) {