ToolRunloopDispatch.kt

src/jvmMain/kotlin/afield/ai/tools/ToolRunloopDispatch.kt · 33 lines

package afield.ai.tools

import afield.runtime.lifecycle.Runloop
import kotlin.coroutines.ContinuationInterceptor
import kotlin.coroutines.coroutineContext

The check that turns a deadlocking aiTool call into an error message.

A tool body runs on the Runloop's main thread, so a caller that is already blocking that thread inside runBlocking can never let the body run: the call would wait for a thread that is waiting for it. Giving the runBlocking a Dispatchers.IO context moves the body but not the blocked caller, so that case is checked as well, by looking for runBlocking on the owning thread's stack. Both messages name the two ways of calling a tool that do work: directly from AI4, or inside start { ... } in box code.

internal suspend fun checkToolRunloopDispatch()

Fail before dispatch when a synchronous caller is preventing the owner from running.

internal suspend fun checkToolRunloopDispatch() {
    check(!Runloop.isMainThread || coroutineContext[ContinuationInterceptor] === Runloop.runLoop.main) {
        "Calling an aiTool from runBlocking on Field's UI thread would deadlock. " +
            "Call the registered tool directly from AI4, or invoke it inside start { ... } in box code."
    }
    // Choosing Dispatchers.IO for runBlocking moves its body, not the blocked caller.
    // The owner is already inside runBlocking before that body's first dispatch.
    val owner = Runloop.mainThread
    check(owner == null || owner === Thread.currentThread() || owner.stackTrace.none {
        it.className.startsWith("kotlinx.coroutines.BuildersKt") && it.methodName.startsWith("runBlocking")
    }) {
        "Calling an aiTool while Field's UI thread is in runBlocking would deadlock, even with Dispatchers.IO. " +
            "Call the registered tool directly from AI4, or invoke it inside start { ... } in box code."
    }
}