Improve TypeScript escaping to handle control characters (#16)

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/generator/typescript.cc

@@ -1,5 +1,6 @@
 #include <sourcemeta/codegen/generator.h>
 
+#include <iomanip> // std::hex, std::setfill, std::setw
 #include <sstream> // std::ostringstream
 
 namespace {
@@ -15,6 +16,12 @@ auto escape_string(const std::string &input) -> std::string {
       case '"':
         result << "\\\"";
         break;
+      case '\b':
+        result << "\\b";
+        break;
+      case '\f':
+        result << "\\f";
+        break;
       case '\n':
         result << "\\n";
         break;
@@ -25,7 +32,13 @@ auto escape_string(const std::string &input) -> std::string {
         result << "\\t";
         break;
       default:
-        result << character;
+        // Escape other control characters (< 0x20) using \uXXXX format
+        if (static_cast<unsigned char>(character) < 0x20) {
+          result << "\\u" << std::hex << std::setfill('0') << std::setw(4)
+                 << static_cast<int>(static_cast<unsigned char>(character));
+        } else {
+          result << character;
+        }
         break;
     }
   }

test/e2e/typescript/2020-12/control_characters_in_property_names/expected.d.ts

@@ -0,0 +1,22 @@
+export type TestWithus = string;
+
+export type TestWithformfeed = string;
+
+export type TestWithbackspace = string;
+
+export type TestWithsoh = string;
+
+export type TestWithnull = string;
+
+export type TestNormal = string;
+
+export type TestAdditionalProperties = never;
+
+export interface Test {
+  "normal"?: TestNormal;
+  "with\bbackspace"?: TestWithbackspace;
+  "with\fformfeed"?: TestWithformfeed;
+  "with\u0000null"?: TestWithnull;
+  "with\u0001soh"?: TestWithsoh;
+  "with\u001fus"?: TestWithus;
+}

test/e2e/typescript/2020-12/control_characters_in_property_names/options.json

@@ -0,0 +1,3 @@
+{
+  "defaultPrefix": "Test"
+}

test/e2e/typescript/2020-12/control_characters_in_property_names/schema.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "type": "object",
+  "properties": {
+    "normal": { "type": "string" },
+    "with\bbackspace": { "type": "string" },
+    "with\fformfeed": { "type": "string" },
+    "with\u0000null": { "type": "string" },
+    "with\u0001soh": { "type": "string" },
+    "with\u001fus": { "type": "string" }
+  },
+  "additionalProperties": false
+}

test/e2e/typescript/2020-12/control_characters_in_property_names/test.ts

@@ -0,0 +1,32 @@
+import { Test } from "./expected";
+
+// Valid: object with control characters in property names
+const validObject: Test = {
+  "normal": "hello",
+  "with\bbackspace": "value1",
+  "with\fformfeed": "value2",
+  "with\u0000null": "value3",
+  "with\u0001soh": "value4",
+  "with\u001fus": "value5"
+};
+
+// Valid: empty object (all properties are optional)
+const emptyObject: Test = {};
+
+// Valid: partial object
+const partialObject: Test = {
+  "normal": "just normal"
+};
+
+// Invalid: extra property not allowed
+const extraProp: Test = {
+  "normal": "hello",
+  // @ts-expect-error - extra property not allowed
+  "extra": "not allowed"
+};
+
+// Invalid: wrong type for property
+const wrongType: Test = {
+  // @ts-expect-error - must be string
+  "normal": 123
+};