Get it back - Data schema spec fix: TSON instead of JSON (#3566) (#3569)

Co-authored-by: Jonathan Dobson <jon.m.dobson@gmail.com>

skyvern-frontend/src/util/tson.ts

@@ -0,0 +1,223 @@
+type JSONValue =
+  | string
+  | number
+  | boolean
+  | null
+  | JSONValue[]
+  | { [key: string]: JSONValue };
+
+interface ParseResult {
+  success: boolean;
+  data?: JSONValue;
+  error?: string;
+}
+
+const placeholder = () => "<STUB>";
+
+/**
+ * TSON ("templated JSON") is a superset of JSON, where double curly braces {{...}} can:
+ *  - exist anywhere outside of string literals, and
+ *  - are treated as placeholders
+ */
+const TSON = {
+  parse(input: string): ParseResult {
+    try {
+      const balanceCheck = checkDoubleBraceBalance(input);
+
+      if (!balanceCheck.balanced) {
+        return {
+          success: false,
+          error: balanceCheck.error,
+        };
+      }
+
+      const pipeline = [
+        replaceBracesOutsideQuotes,
+        // removeTrailingCommas,
+        JSON.parse,
+      ];
+
+      const parsed = pipeline.reduce((acc, fn) => fn(acc), input) as JSONValue;
+
+      return {
+        success: true,
+        data: parsed,
+      };
+    } catch (error) {
+      return {
+        success: false,
+        error: error instanceof Error ? error.message : String(error),
+      };
+    }
+  },
+};
+
+function checkDoubleBraceBalance(input: string): {
+  balanced: boolean;
+  error?: string;
+} {
+  let inString = false;
+  let escapeNext = false;
+  let depth = 0;
+
+  for (let i = 0; i < input.length; i++) {
+    const char = input[i];
+    const nextChar = input[i + 1];
+
+    // handle escape sequences
+    if (escapeNext) {
+      escapeNext = false;
+      continue;
+    }
+
+    if (char === "\\") {
+      escapeNext = true;
+      continue;
+    }
+
+    // inside-string tracking
+    if (char === '"') {
+      inString = !inString;
+      continue;
+    }
+
+    // double braces counts (only outside strings)
+    if (!inString) {
+      if (char === "{" && nextChar === "{") {
+        depth++;
+        i++; // skip next char
+      } else if (char === "}" && nextChar === "}") {
+        depth--;
+        if (depth < 0) {
+          return {
+            balanced: false,
+            error: `Unmatched closing }} at position ${i}`,
+          };
+        }
+        i++; // skip next char
+      }
+    }
+  }
+
+  if (depth > 0) {
+    return {
+      balanced: false,
+      error: `Unclosed {{ - missing ${depth} closing }}`,
+    };
+  }
+
+  return { balanced: true };
+}
+
+function replaceBracesOutsideQuotes(input: string): string {
+  let result = "";
+  let inString = false;
+  let escapeNext = false;
+  let inDoubleBrace = 0; // track nesting depth of {{...}}
+
+  for (let i = 0; i < input.length; i++) {
+    const char = input[i];
+    const nextChar = input[i + 1];
+
+    // escape sequences
+    if (escapeNext) {
+      if (inDoubleBrace === 0) {
+        result += char;
+      }
+      escapeNext = false;
+      continue;
+    }
+
+    if (char === "\\") {
+      if (inDoubleBrace === 0) {
+        result += char;
+      }
+      escapeNext = true;
+      continue;
+    }
+
+    // inside-string tracking
+    if (char === '"') {
+      inString = !inString;
+      if (inDoubleBrace === 0) {
+        result += char;
+      }
+      continue;
+    }
+
+    // double braces (only outside strings)
+    if (!inString) {
+      if (char === "{" && nextChar === "{") {
+        if (inDoubleBrace === 0) {
+          result += `"${placeholder()}"`;
+        }
+        inDoubleBrace++;
+        i++; // skip next char
+        continue;
+      } else if (char === "}" && nextChar === "}") {
+        inDoubleBrace--;
+        i++; // skip next char
+        continue;
+      }
+    }
+
+    // add characters when we're not inside double braces
+    if (inDoubleBrace === 0) {
+      result += char;
+    }
+  }
+
+  return result;
+}
+
+export function removeTrailingCommas(input: string): string {
+  let result = "";
+  let inString = false;
+  let escapeNext = false;
+
+  for (let i = 0; i < input.length; i++) {
+    const char = input[i];
+
+    // escape sequences
+    if (escapeNext) {
+      result += char;
+      escapeNext = false;
+      continue;
+    }
+
+    if (char === "\\") {
+      result += char;
+      escapeNext = true;
+      continue;
+    }
+
+    // inside-string tracking
+    if (char === '"') {
+      inString = !inString;
+      result += char;
+      continue;
+    }
+
+    // check for trailing commas (outside strings)
+    if (!inString && char === ",") {
+      // look-ahead for the next non-whitespace character
+      let j = i + 1;
+      // eslint-disable-next-line @typescript-eslint/ban-ts-comment
+      // @ts-ignore
+      while (j < input.length && /\s/.test(input[j])) {
+        j++;
+      }
+
+      // if next non-whitespace is } or ], skip the comma
+      if (j < input.length && (input[j] === "}" || input[j] === "]")) {
+        continue; // Skip this comma
+      }
+    }
+
+    result += char;
+  }
+
+  return result;
+}
+
+export { TSON };