harn_vm/composition/
hosts.rs

1use std::collections::BTreeMap;
2
3use serde_json::Value;
4
5use crate::agent_events::ToolCallErrorCategory;
6use crate::value::VmValue;
7use crate::vm::AsyncBuiltinCtx;
8use crate::VmClosure;
9
10use super::manifest::BindingManifestEntry;
11use super::types::{CompositionToolHost, CompositionToolOutput};
12
13pub struct StaticCompositionToolHost {
14    outputs: BTreeMap<String, Value>,
15}
16
17impl StaticCompositionToolHost {
18    pub fn new(outputs: BTreeMap<String, Value>) -> Self {
19        Self { outputs }
20    }
21}
22
23#[async_trait::async_trait(?Send)]
24impl CompositionToolHost for StaticCompositionToolHost {
25    async fn call(&self, binding: &BindingManifestEntry, input: Value) -> CompositionToolOutput {
26        if let Some(value) = self.outputs.get(&binding.name) {
27            return CompositionToolOutput::ok(value.clone());
28        }
29        if let Some(value) = binding.metadata.get("mock_output") {
30            return CompositionToolOutput::ok(value.clone());
31        }
32        CompositionToolOutput::ok(serde_json::json!({
33            "tool": binding.name,
34            "input": input,
35        }))
36    }
37}
38
39/// Dispatches every binding call to a caller-supplied Harn closure.
40///
41/// The closure is compiled in the calling VM and receives
42/// `(binding_name: string, input: dict)`. Returning a value yields a successful
43/// child result; raising an error fails the child call. Each invocation runs
44/// on a fresh clone of the outer VM so closure-side builtins (`host_call`,
45/// pipeline imports, etc.) resolve normally — the inner composition VM only
46/// sees the manifest bindings plus pure helpers.
47pub struct ClosureCompositionToolHost {
48    closure: VmClosure,
49    ctx: AsyncBuiltinCtx,
50}
51
52impl ClosureCompositionToolHost {
53    pub fn new(closure: VmClosure, ctx: AsyncBuiltinCtx) -> Self {
54        Self { closure, ctx }
55    }
56}
57
58#[async_trait::async_trait(?Send)]
59impl CompositionToolHost for ClosureCompositionToolHost {
60    async fn call(&self, binding: &BindingManifestEntry, input: Value) -> CompositionToolOutput {
61        let mut vm = self.ctx.child_vm();
62        let args = vec![
63            VmValue::String(std::sync::Arc::from(binding.name.as_str())),
64            crate::json_to_vm_value(&input),
65        ];
66        let result = vm.call_closure_pub(&self.closure, &args).await;
67        self.ctx.forward_output(&vm.take_output());
68        match result {
69            Ok(value) => {
70                let json = crate::llm::vm_value_to_json(&value);
71                CompositionToolOutput::ok(json)
72            }
73            Err(error) => {
74                CompositionToolOutput::error(error.to_string(), ToolCallErrorCategory::ToolError)
75            }
76        }
77    }
78}
harn_vm/composition/hosts.rs

harn_vm/composition/
hosts.rs
