From cf0b7271936380d3780b67b6e59038276f0d9d5d Mon Sep 17 00:00:00 2001
From: Pat Hickey <p.hickey@f5.com>
Date: Fri, 5 Jun 2026 17:13:15 -0700
Subject: [PATCH] wizer: support init func as a wave function call (components
 only)

---
 crates/wizer/Cargo.toml                |  3 ++
 crates/wizer/src/component/wasmtime.rs | 61 ++++++++++++++++++++------
 2 files changed, 51 insertions(+), 13 deletions(-)

diff --git a/crates/wizer/Cargo.toml b/crates/wizer/Cargo.toml
index c237a743523c..9f76326c3e83 100644
--- a/crates/wizer/Cargo.toml
+++ b/crates/wizer/Cargo.toml
@@ -62,6 +62,9 @@ wasmtime = [
   'wasmtime/gc',
   'wasmtime/gc-null',
   'wasmtime/async',
+  # Need wave and wit-parser features to parse init func expressions
+  'wasmtime/wave',
+  'wasmtime/wit-parser',
 ]
 
 # Enable support for wizening components.
diff --git a/crates/wizer/src/component/wasmtime.rs b/crates/wizer/src/component/wasmtime.rs
index 8c12d86bac22..15a7254990bb 100644
--- a/crates/wizer/src/component/wasmtime.rs
+++ b/crates/wizer/src/component/wasmtime.rs
@@ -1,7 +1,7 @@
 use crate::Wizer;
 use crate::component::ComponentInstanceState;
 use wasmtime::component::{
-    Component, ComponentExportIndex, Instance, Lift, WasmList, types::ComponentItem,
+    Component, ComponentExportIndex, Instance, Lift, Val, WasmList, types::ComponentItem,
 };
 use wasmtime::{Result, Store, error::Context as _, format_err};
 
@@ -27,10 +27,10 @@ impl Wizer {
         let engine = store.engine();
         let component = Component::new(engine, &instrumented_wasm)
             .context("failed to compile the Wasm component")?;
-        let index = self.validate_component_init_func(&component)?;
+        let (index, args, rets) = self.validate_component_init_func(&component)?;
 
         let instance = instantiate(store, &component).await?;
-        self.initialize_component(store, &instance, index).await?;
+        self.initialize_component(store, &instance, index, args, rets).await?;
         self.snapshot_component(cx, &mut WasmtimeWizerComponent { store, instance })
             .await
     }
@@ -38,10 +38,31 @@ impl Wizer {
     fn validate_component_init_func(
         &self,
         component: &Component,
-    ) -> wasmtime::Result<ComponentExportIndex> {
+    ) -> wasmtime::Result<(ComponentExportIndex, Vec<Val>, Vec<Val>)> {
         let init_func = self.get_init_func();
+
+        use wasmtime::component::wasm_wave::{untyped::UntypedFuncCall, wasm::WasmFunc};
+        use wasmtime::component::wit_parser::ItemName;
+        let (func_name, func_call) = if init_func.contains('(') {
+            let call = UntypedFuncCall::parse(init_func)
+                .with_context(|| format!("parsing `{init_func}` as wave function call"))?;
+            let item_name = call
+                .item_name()
+                .map_err(wasmtime::Error::from_anyhow)
+                .with_context(|| format!("parsing `{init_func}` as wave function call"))?;
+            (item_name, Some(call))
+        } else {
+            (
+                init_func
+                    .parse::<ItemName>()
+                    .map_err(wasmtime::Error::from_anyhow)
+                    .with_context(|| format!("parsing `{init_func}` as wit item name"))?,
+                None,
+            )
+        };
+
         let (ty, index) = component
-            .get_export(None, init_func)
+            .get_export(None, func_name)
             .ok_or_else(|| format_err!("the component does export the function `{init_func}`"))?;
 
         let ty = match ty {
@@ -49,12 +70,24 @@ impl Wizer {
             _ => wasmtime::bail!("the component's `{init_func}` export is not a function",),
         };
 
-        if ty.params().len() != 0 || ty.results().len() != 0 {
-            wasmtime::bail!(
-                "the component's `{init_func}` function export does not have type `[] -> []`",
-            );
+        if let Some(func_call) = func_call {
+            let param_types = WasmFunc::params(&ty).collect::<Vec<_>>();
+            let param_vals = func_call.to_wasm_params(&param_types).with_context(|| {
+                format!("parsing `{init_func}` params as types {param_types:?}")
+            })?;
+            Ok((
+                index,
+                param_vals,
+                vec![Val::Bool(false); ty.results().len()],
+            ))
+        } else {
+            if ty.params().len() != 0 || ty.results().len() != 0 {
+                wasmtime::bail!(
+                    "the component's `{init_func}` function export does not have type `[] -> []`",
+                );
+            }
+            Ok((index, vec![], vec![]))
         }
-        Ok(index)
     }
 
     async fn initialize_component<T: Send>(
@@ -62,15 +95,17 @@ impl Wizer {
         store: &mut Store<T>,
         instance: &Instance,
         index: ComponentExportIndex,
+        args: Vec<Val>,
+        mut rets: Vec<Val>,
     ) -> wasmtime::Result<()> {
         let init_func = instance
-            .get_typed_func::<(), ()>(&mut *store, index)
+            .get_func(&mut *store, index)
             .expect("checked by `validate_init_func`");
         init_func
-            .call_async(&mut *store, ())
+            .call_async(&mut *store, &args, &mut rets)
             .await
             .with_context(|| format!("the initialization function trapped"))?;
-
+        // TODO: do we want some way to report the values of `rets` back up?
         Ok(())
     }
 }