Merge #968

968: Added invoke option to the command r=syrusakbary a=syrusakbary

# Description 

This PR adds an `--invoke` to the Wasmer CLI

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# Review

- [x] Add a short description of the the change to the CHANGELOG.md file


Co-authored-by: Syrus <me@syrusakbary.com>

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## **[Unreleased]**
 
+- [#968](https://github.com/wasmerio/wasmer/pull/968) Added `--invoke` option to the command
 - [#960](https://github.com/wasmerio/wasmer/pull/960) Fix `runtime-c-api` header files when compiled by clang.
 - [#925](https://github.com/wasmerio/wasmer/pull/925) Host functions can be closures with a captured environment.
 - [#917](https://github.com/wasmerio/wasmer/pull/917) Host functions (aka imported functions) may not have `&mut vm::Ctx` as first argument, i.e. the presence of the `&mut vm::Ctx` argument is optional.

src/bin/wasmer.rs

@@ -132,6 +132,10 @@ struct Run {
     )]
     backend: Backend,
 
+    /// Invoke a specified function
+    #[structopt(long = "invoke", short = "i")]
+    invoke: Option<String>,
+
     /// Emscripten symbol map
     #[structopt(long = "em-symbol-map", parse(from_os_str), group = "emscripten")]
     em_symbol_map: Option<PathBuf>,
@@ -683,8 +687,12 @@ fn execute_wasm(options: &Run) -> Result<(), String> {
                 args.push(Value::I32(x));
             }
 
+            let invoke_fn = match options.invoke.as_ref() {
+                Some(fun) => fun,
+                _ => "main",
+            };
             instance
-                .dyn_func("main")
+                .dyn_func(&invoke_fn)
                 .map_err(|e| format!("{:?}", e))?
                 .call(&args)
                 .map_err(|e| format!("{:?}", e))?;