Fix Python codegen

Co-Authored-By: Copilot <223556219+Copilot@users.noreply.github.com>

Author: SteveSandersonMS

python/copilot/generated/rpc.py

@@ -1593,7 +1593,7 @@ class SessionUIElicitationResult:
     action: Action
     """The user's response: accept (submitted), decline (rejected), or cancel (dismissed)"""
 
-    content: Optional[dict[str, float | bool | list[str] | str]] = None
+    content: dict[str, float | bool | list[str] | str] | None = None
     """The form values submitted by the user (present when action is 'accept')"""
 
     @staticmethod
@@ -1696,7 +1696,7 @@ class PropertyType(Enum):
 @dataclass
 class Property:
     type: PropertyType
-    default: Optional[float | bool | list[str] | str] = None
+    default: float | bool | list[str] | str | None = None
     description: str | None = None
     enum: list[str] | None = None
     enum_names: list[str] | None = None

scripts/codegen/python.ts

@@ -32,12 +32,37 @@ import {
  * - Callable from collections.abc instead of typing
  * - Clean up unused typing imports
  */
+function replaceBalancedBrackets(code: string, prefix: string, replacer: (inner: string) => string): string {
+    let result = "";
+    let i = 0;
+    while (i < code.length) {
+        const idx = code.indexOf(prefix + "[", i);
+        if (idx === -1) {
+            result += code.slice(i);
+            break;
+        }
+        result += code.slice(i, idx);
+        const start = idx + prefix.length + 1; // after '['
+        let depth = 1;
+        let j = start;
+        while (j < code.length && depth > 0) {
+            if (code[j] === "[") depth++;
+            else if (code[j] === "]") depth--;
+            j++;
+        }
+        const inner = code.slice(start, j - 1);
+        result += replacer(inner);
+        i = j;
+    }
+    return result;
+}
+
 function modernizePython(code: string): string {
-    // Replace Optional[X] with X | None (handles nested brackets)
-    code = code.replace(/Optional\[([^\[\]]*(?:\[[^\[\]]*\])*[^\[\]]*)\]/g, "$1 | None");
+    // Replace Optional[X] with X | None (handles arbitrarily nested brackets)
+    code = replaceBalancedBrackets(code, "Optional", (inner) => `${inner} | None`);
 
     // Replace Union[X, Y] with X | Y
-    code = code.replace(/Union\[([^\[\]]*(?:\[[^\[\]]*\])*[^\[\]]*)\]/g, (_match, inner: string) => {
+    code = replaceBalancedBrackets(code, "Union", (inner) => {
         return inner.split(",").map((s: string) => s.trim()).join(" | ");
     });