Fix regression in binding simple parameters

bindparam.go

@@ -155,16 +155,21 @@ func BindStyledParameterWithOptions(style string, paramName string, value string
 		return bindSplitPartsToDestinationArray(parts, dest)
 	}
 
-	// For primitive types, we still need to strip style prefixes (e.g. label's
-	// leading "." or matrix's ";paramName=") before binding.
-	parts, err := splitStyledParameter(style, opts.Explode, false, paramName, value)
-	if err != nil {
-		return fmt.Errorf("error splitting parameter '%s': %w", paramName, err)
-	}
-	if len(parts) != 1 {
-		return fmt.Errorf("parameter '%s': expected single value, got %d parts", paramName, len(parts))
+	// For primitive types, only label and matrix styles need prefix stripping
+	// via splitStyledParameter. Simple and form styles can bind the raw value
+	// directly — splitting on commas would incorrectly reject primitive values
+	// that contain commas (see https://github.com/oapi-codegen/runtime/issues/114).
+	if style == "label" || style == "matrix" {
+		parts, err := splitStyledParameter(style, opts.Explode, false, paramName, value)
+		if err != nil {
+			return fmt.Errorf("error splitting parameter '%s': %w", paramName, err)
+		}
+		if len(parts) != 1 {
+			return fmt.Errorf("parameter '%s': expected single value, got %d parts", paramName, len(parts))
+		}
+		value = parts[0]
 	}
-	return BindStringToObject(parts[0], dest)
+	return BindStringToObject(value, dest)
 }
 
 // This is a complex set of operations, but each given parameter style can be

bindparam_test.go

@@ -1284,3 +1284,54 @@ func TestBindStyledParameterWithLocation(t *testing.T) {
 		assert.EqualValues(t, expectedMap, dstMap)
 	})
 }
+
+// TestBindStyledParameter_HeaderWithCommas reproduces
+// https://github.com/oapi-codegen/runtime/issues/114
+// Header parameters using simple style should accept string values containing
+// commas without treating them as array delimiters.
+func TestBindStyledParameter_HeaderWithCommas(t *testing.T) {
+	t.Run("primitive string with commas", func(t *testing.T) {
+		var dest string
+		// A JSON string header value that happens to contain commas.
+		err := BindStyledParameterWithOptions("simple", "X-My-Header", `{"key":"value","other":"data"}`, &dest, BindStyledParameterOptions{
+			ParamLocation: ParamLocationHeader,
+			Explode:       false,
+			Required:      true,
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, `{"key":"value","other":"data"}`, dest)
+	})
+
+	t.Run("primitive string with many commas", func(t *testing.T) {
+		var dest string
+		err := BindStyledParameterWithOptions("simple", "X-My-Header", "a,b,c,d,e", &dest, BindStyledParameterOptions{
+			ParamLocation: ParamLocationHeader,
+			Explode:       false,
+			Required:      true,
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, "a,b,c,d,e", dest)
+	})
+
+	t.Run("primitive string without commas still works", func(t *testing.T) {
+		var dest string
+		err := BindStyledParameterWithOptions("simple", "X-My-Header", "simple-value", &dest, BindStyledParameterOptions{
+			ParamLocation: ParamLocationHeader,
+			Explode:       false,
+			Required:      true,
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, "simple-value", dest)
+	})
+
+	t.Run("array of strings still splits on commas", func(t *testing.T) {
+		var dest []string
+		err := BindStyledParameterWithOptions("simple", "X-My-Header", "a,b,c", &dest, BindStyledParameterOptions{
+			ParamLocation: ParamLocationHeader,
+			Explode:       false,
+			Required:      true,
+		})
+		assert.NoError(t, err)
+		assert.Equal(t, []string{"a", "b", "c"}, dest)
+	})
+}