fix(coding-agent): make config env references explicit

closes #5095

packages/coding-agent/src/core/resolve-config-value.ts

@@ -8,18 +8,151 @@ import { getShellConfig } from "../utils/shell.ts";
 
 // Cache for shell command results (persists for process lifetime)
 const commandResultCache = new Map<string, string | undefined>();
+const ENV_VAR_NAME_RE = /^[A-Za-z_][A-Za-z0-9_]*$/;
+const ENV_VAR_NAME_PREFIX_RE = /^[A-Za-z_][A-Za-z0-9_]*/;
+const LEGACY_ENV_VAR_NAME_RE = /^[A-Z_][A-Z0-9_]*$/;
+
+type TemplatePart = { type: "literal"; value: string } | { type: "env"; name: string };
+
+type ConfigValueReference = { type: "command"; config: string } | { type: "template"; parts: TemplatePart[] };
+
+function appendLiteral(parts: TemplatePart[], value: string): void {
+	if (!value) return;
+	const previousPart = parts[parts.length - 1];
+	if (previousPart?.type === "literal") {
+		previousPart.value += value;
+		return;
+	}
+	parts.push({ type: "literal", value });
+}
+
+function parseConfigValueTemplate(config: string): TemplatePart[] {
+	const parts: TemplatePart[] = [];
+	let index = 0;
+
+	while (index < config.length) {
+		const dollarIndex = config.indexOf("$", index);
+		if (dollarIndex < 0) {
+			appendLiteral(parts, config.slice(index));
+			break;
+		}
+
+		appendLiteral(parts, config.slice(index, dollarIndex));
+		const nextChar = config[dollarIndex + 1];
+
+		if (nextChar === "$" || nextChar === "!") {
+			appendLiteral(parts, nextChar);
+			index = dollarIndex + 2;
+			continue;
+		}
+
+		if (nextChar === "{") {
+			const endIndex = config.indexOf("}", dollarIndex + 2);
+			if (endIndex < 0) {
+				appendLiteral(parts, "$");
+				index = dollarIndex + 1;
+				continue;
+			}
+
+			const name = config.slice(dollarIndex + 2, endIndex);
+			if (ENV_VAR_NAME_RE.test(name)) {
+				parts.push({ type: "env", name });
+			} else {
+				appendLiteral(parts, config.slice(dollarIndex, endIndex + 1));
+			}
+			index = endIndex + 1;
+			continue;
+		}
+
+		const match = config.slice(dollarIndex + 1).match(ENV_VAR_NAME_PREFIX_RE);
+		if (match) {
+			parts.push({ type: "env", name: match[0] });
+			index = dollarIndex + 1 + match[0].length;
+			continue;
+		}
+
+		appendLiteral(parts, "$");
+		index = dollarIndex + 1;
+	}
+
+	return parts;
+}
+
+function parseConfigValueReference(config: string): ConfigValueReference {
+	if (config.startsWith("!")) {
+		return { type: "command", config };
+	}
+
+	return { type: "template", parts: parseConfigValueTemplate(config) };
+}
+
+function resolveEnvConfigValue(name: string): string | undefined {
+	return process.env[name] || undefined;
+}
+
+function getTemplateEnvVarNames(parts: TemplatePart[]): string[] {
+	const names: string[] = [];
+	for (const part of parts) {
+		if (part.type !== "env" || names.includes(part.name)) continue;
+		names.push(part.name);
+	}
+	return names;
+}
+
+function resolveTemplate(parts: TemplatePart[]): string | undefined {
+	let resolved = "";
+	for (const part of parts) {
+		if (part.type === "literal") {
+			resolved += part.value;
+			continue;
+		}
+		const envValue = resolveEnvConfigValue(part.name);
+		if (envValue === undefined) return undefined;
+		resolved += envValue;
+	}
+	return resolved;
+}
+
+export function getConfigValueEnvVarName(config: string): string | undefined {
+	const reference = parseConfigValueReference(config);
+	if (reference.type !== "template") return undefined;
+	return reference.parts.length === 1 && reference.parts[0]?.type === "env" ? reference.parts[0].name : undefined;
+}
+
+export function getConfigValueEnvVarNames(config: string): string[] {
+	const reference = parseConfigValueReference(config);
+	return reference.type === "template" ? getTemplateEnvVarNames(reference.parts) : [];
+}
+
+export function getMissingConfigValueEnvVarNames(config: string): string[] {
+	return getConfigValueEnvVarNames(config).filter((name) => resolveEnvConfigValue(name) === undefined);
+}
+
+export function isCommandConfigValue(config: string): boolean {
+	return parseConfigValueReference(config).type === "command";
+}
+
+export function isConfigValueConfigured(config: string): boolean {
+	return getMissingConfigValueEnvVarNames(config).length === 0;
+}
+
+export function isLegacyEnvVarNameConfigValue(config: string): boolean {
+	return LEGACY_ENV_VAR_NAME_RE.test(config);
+}
 
 /**
  * Resolve a config value (API key, header value, etc.) to an actual value.
  * - If starts with "!", executes the rest as a shell command and uses stdout (cached)
- * - Otherwise checks environment variable first, then treats as literal (not cached)
+ * - Interpolates "$ENV_VAR" or "${ENV_VAR}" references with the named environment variable
+ * - In non-command values, "$$" escapes a literal "$" and "$!" escapes a literal "!"
+ * - Otherwise treats the value as a literal
  */
 export function resolveConfigValue(config: string): string | undefined {
-	if (config.startsWith("!")) {
-		return executeCommand(config);
+	const reference = parseConfigValueReference(config);
+	if (reference.type === "command") {
+		return executeCommand(reference.config);
 	}
-	const envValue = process.env[config];
-	return envValue || config;
+	return resolveTemplate(reference.parts);
 }
 
 function executeWithConfiguredShell(command: string): { executed: boolean; value: string | undefined } {
@@ -89,11 +222,11 @@ function executeCommand(commandConfig: string): string | undefined {
  * Resolve all header values using the same resolution logic as API keys.
  */
 export function resolveConfigValueUncached(config: string): string | undefined {
-	if (config.startsWith("!")) {
-		return executeCommandUncached(config);
+	const reference = parseConfigValueReference(config);
+	if (reference.type === "command") {
+		return executeCommandUncached(reference.config);
 	}
-	const envValue = process.env[config];
-	return envValue || config;
+	return resolveTemplate(reference.parts);
 }
 
 export function resolveConfigValueOrThrow(config: string, description: string): string {
@@ -102,8 +235,19 @@ export function resolveConfigValueOrThrow(config: string, description: string):
 		return resolvedValue;
 	}
 
-	if (config.startsWith("!")) {
-		throw new Error(`Failed to resolve ${description} from shell command: ${config.slice(1)}`);
+	const reference = parseConfigValueReference(config);
+	if (reference.type === "command") {
+		throw new Error(`Failed to resolve ${description} from shell command: ${reference.config.slice(1)}`);
+	}
+
+	if (reference.type === "template") {
+		const missingEnvVars = getMissingConfigValueEnvVarNames(config);
+		if (missingEnvVars.length === 1) {
+			throw new Error(`Failed to resolve ${description} from environment variable: ${missingEnvVars[0]}`);
+		}
+		if (missingEnvVars.length > 1) {
+			throw new Error(`Failed to resolve ${description} from environment variables: ${missingEnvVars.join(", ")}`);
+		}
 	}
 
 	throw new Error(`Failed to resolve ${description}`);