Function getCanUseToolFn

src/cli/print.ts:4267–4334

(
  permissionPromptToolName: string | undefined,
  structuredIO: StructuredIO,
  getMcpTools: () => Tool[],
  onPermissionPrompt?: (details: RequiresActionDetails) => void,
)

// Exported for testing — regression: this used to crash at construction when
// getMcpTools() was empty (before per-server connects populated appState).
export function getCanUseToolFn(
  permissionPromptToolName: string | undefined,
  structuredIO: StructuredIO,
  getMcpTools: () => Tool[],
  onPermissionPrompt?: (details: RequiresActionDetails) => void,
): CanUseToolFn {
  if (permissionPromptToolName === 'stdio') {
    return structuredIO.createCanUseTool(onPermissionPrompt)
  }
  if (!permissionPromptToolName) {
    return async (
      tool,
      input,
      toolUseContext,
      assistantMessage,
      toolUseId,
      forceDecision,
    ) =>
      forceDecision ??
      (await hasPermissionsToUseTool(
        tool,
        input,
        toolUseContext,
        assistantMessage,
        toolUseId,
      ))
  }
  // Lazy lookup: MCP connects are per-server incremental in print mode, so
  // the tool may not be in appState yet at init time. Resolve on first call
  // (first permission prompt), by which point connects have had time to finish.
  let resolved: CanUseToolFn | null = null
  return async (
    tool,
    input,
    toolUseContext,
    assistantMessage,
    toolUseId,
    forceDecision,
  ) => {
    if (!resolved) {
      const mcpTools = getMcpTools()
      const permissionPromptTool = mcpTools.find(t =>
        toolMatchesName(t, permissionPromptToolName),
      ) as PermissionPromptTool | undefined
      if (!permissionPromptTool) {
        const error = `Error: MCP tool ${permissionPromptToolName} (passed via --permission-prompt-tool) not found. Available MCP tools: ${mcpTools.map(t => t.name).join(', ') || 'none'}`
        process.stderr.write(`${error}\n`)
        gracefulShutdownSync(1)
        throw new Error(error)
      }
      if (!permissionPromptTool.inputJSONSchema) {
        const error = `Error: tool ${permissionPromptToolName} (passed via --permission-prompt-tool) must be an MCP tool`
        process.stderr.write(`${error}\n`)
        gracefulShutdownSync(1)
        throw new Error(error)
      }
      resolved = createCanUseToolWithPermissionPrompt(permissionPromptTool)
    }