From 2df2e1dfd8bf2f91ff8336327623bac3b174cc49 Mon Sep 17 00:00:00 2001
From: Bruce Arctor <5032356+brucearctor@users.noreply.github.com>
Date: Mon, 11 May 2026 20:40:15 -0700
Subject: [PATCH] fix: escape ${expression} in formatString description to
 prevent ADK KeyError

The formatString function description in basic_catalog.json contained
the literal text ${expression}, which the ADK's inject_session_state()
regex (r'{+[^{}]*}+') matched as a template variable. Since 'expression'
passes Python's str.isidentifier() check, the ADK attempted to look it
up in the session state dict and raised a KeyError when not found.

Changed ${expression} to ${<expression>} so that '<expression>' fails
the isidentifier() check, causing the ADK to skip it (returning the
match as-is). The other interpolation examples in the description
(${/absolute/path}, ${now()}, etc.) were already safe because they
contain characters (/, parentheses) that make them invalid identifiers.

Fixes #1388
---
 specification/v0_10/json/basic_catalog.json | 2 +-
 specification/v0_9/json/basic_catalog.json  | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/specification/v0_10/json/basic_catalog.json b/specification/v0_10/json/basic_catalog.json
index fdf602abd..926c611eb 100644
--- a/specification/v0_10/json/basic_catalog.json
+++ b/specification/v0_10/json/basic_catalog.json
@@ -811,7 +811,7 @@
     },
     "formatString": {
       "type": "object",
-      "description": "Performs string interpolation of data model values and other functions in the catalog functions list and returns the resulting string. The value string can contain interpolated expressions in the `${expression}` format. Supported expression types include: JSON Pointer paths to the data model (e.g., `${/absolute/path}` or `${relative/path}`), and client-side function calls (e.g., `${now()}`). Function arguments must be named (e.g., `${formatDate(value:${/currentDate}, format:'MM-dd')}`). To include a literal `${` sequence, escape it as `\\${`.",
+      "description": "Performs string interpolation of data model values and other functions in the catalog functions list and returns the resulting string. The value string can contain interpolated expressions in the `${<expression>}` format. Supported expression types include: JSON Pointer paths to the data model (e.g., `${/absolute/path}` or `${relative/path}`), and client-side function calls (e.g., `${now()}`). Function arguments must be named (e.g., `${formatDate(value:${/currentDate}, format:'MM-dd')}`). To include a literal `${` sequence, escape it as `\\${`.",
       "properties": {
         "call": {
           "const": "formatString"
diff --git a/specification/v0_9/json/basic_catalog.json b/specification/v0_9/json/basic_catalog.json
index bbb7d83a3..f2d8386f4 100644
--- a/specification/v0_9/json/basic_catalog.json
+++ b/specification/v0_9/json/basic_catalog.json
@@ -962,7 +962,7 @@
     },
     "formatString": {
       "type": "object",
-      "description": "Performs string interpolation of data model values and other functions in the catalog functions list and returns the resulting string. The value string can contain interpolated expressions in the `${expression}` format. Supported expression types include: JSON Pointer paths to the data model (e.g., `${/absolute/path}` or `${relative/path}`), and client-side function calls (e.g., `${now()}`). Function arguments must be named (e.g., `${formatDate(value:${/currentDate}, format:'MM-dd')}`). To include a literal `${` sequence, escape it as `\\${`.",
+      "description": "Performs string interpolation of data model values and other functions in the catalog functions list and returns the resulting string. The value string can contain interpolated expressions in the `${<expression>}` format. Supported expression types include: JSON Pointer paths to the data model (e.g., `${/absolute/path}` or `${relative/path}`), and client-side function calls (e.g., `${now()}`). Function arguments must be named (e.g., `${formatDate(value:${/currentDate}, format:'MM-dd')}`). To include a literal `${` sequence, escape it as `\\${`.",
       "properties": {
         "call": {
           "const": "formatString"