From d058b3debfa791abade2d4fd69fc74a3b4dca7ec Mon Sep 17 00:00:00 2001
From: yanganto <yanganto@gmail.com>
Date: Mon, 25 Nov 2019 14:24:39 +0800
Subject: [PATCH] Set default stdout of wasm to `console.log`

The print function of wasm will be
	- `console.log` by default or when giving undefined or "console"
	- a dumb function when giving `null`
	- the function when giving a function

Co-Authored-By: Noah <33094578+coolreader18@users.noreply.github.com>
---
 wasm/lib/README.md       |  5 +++--
 wasm/lib/src/lib.rs      | 17 +++++------------
 wasm/lib/src/vm_class.rs |  4 +++-
 3 files changed, 11 insertions(+), 15 deletions(-)

diff --git a/wasm/lib/README.md b/wasm/lib/README.md
index fc40074a44..012351abb6 100644
--- a/wasm/lib/README.md
+++ b/wasm/lib/README.md
@@ -33,8 +33,9 @@ pyEval(code, options?);
 -   `vars?`: `{ [key: string]: any }`: Variables passed to the VM that can be
     accessed in Python with the variable `js_vars`. Functions do work, and
     receive the Python kwargs as the `this` argument.
--   `stdout?`: `(out: string) => void`: A function to replace the native print
-    function, by default `console.log`.
+-   `stdout?`: `"console" | ((out: string) => void) | null`: A function to replace the
+    native print function, and it will be `console.log` when giving `undefined`
+    or "console", and it will be a dumb function when giving null.
 
 ## License
 
diff --git a/wasm/lib/src/lib.rs b/wasm/lib/src/lib.rs
index e750ef977a..b1f55d36bc 100644
--- a/wasm/lib/src/lib.rs
+++ b/wasm/lib/src/lib.rs
@@ -61,8 +61,10 @@ const TS_CMT_START: &'static str = "/*";
 /// -   `vars?`: `{ [key: string]: any }`: Variables passed to the VM that can be
 ///     accessed in Python with the variable `js_vars`. Functions do work, and
 ///     receive the Python kwargs as the `this` argument.
-/// -   `stdout?`: `(out: string) => void`: A function to replace the native print
-///     function, by default `console.log`.
+/// -   `stdout?`: `"console" | ((out: string) => void) | null`: A function to replace the
+///     native print native print function, and it will be `console.log` when giving
+///     `undefined` or "console", and it will be a dumb function when giving null.
+
 pub fn eval_py(source: &str, options: Option<Object>) -> Result<JsValue, JsValue> {
     let options = options.unwrap_or_else(Object::new);
     let js_vars = {
@@ -75,18 +77,9 @@ pub fn eval_py(source: &str, options: Option<Object>) -> Result<JsValue, JsValue
             return Err(TypeError::new("vars must be an object").into());
         }
     };
-    let stdout = {
-        let prop = Reflect::get(&options, &"stdout".into())?;
-        if prop.is_undefined() {
-            None
-        } else {
-            Some(prop)
-        }
-    };
-
     let vm = VMStore::init(PY_EVAL_VM_ID.into(), Some(true));
 
-    vm.set_stdout(stdout.unwrap_or(JsValue::UNDEFINED))?;
+    vm.set_stdout(Reflect::get(&options, &"stdout".into())?)?;
 
     if let Some(js_vars) = js_vars {
         vm.add_to_scope("js_vars".into(), js_vars.into())?;
diff --git a/wasm/lib/src/vm_class.rs b/wasm/lib/src/vm_class.rs
index 1f2584f0a6..d3e0600596 100644
--- a/wasm/lib/src/vm_class.rs
+++ b/wasm/lib/src/vm_class.rs
@@ -230,11 +230,13 @@ impl WASMVirtualMachine {
                         .map_err(|err| convert::js_to_py(vm, err))?;
                         Ok(vm.get_none())
                     })
-            } else if stdout.is_undefined() || stdout.is_null() {
+            } else if stdout.is_null() {
                 fn noop(vm: &VirtualMachine, _args: PyFuncArgs) -> PyResult {
                     Ok(vm.get_none())
                 }
                 vm.ctx.new_rustfunc(noop)
+            } else if stdout.is_undefined() {
+                vm.ctx.new_rustfunc(wasm_builtins::builtin_print_console)
             } else {
                 return Err(error());
             };