RustPython · shinglyu · Dec 3, 2018 · Nov 21, 2018
diff --git a/vm/src/vm.rs b/vm/src/vm.rs
@@ -31,7 +31,7 @@ use super::sysmodule;
 /// Top level container of a python virtual machine. In theory you could
 /// create more instances of this struct and have them operate fully isolated.
 pub struct VirtualMachine {
-    builtins: PyObjectRef,
+    pub builtins: PyObjectRef,
     pub sys_module: PyObjectRef,
     pub stdlib_inits: HashMap<String, stdlib::StdlibInitFunc>,
     pub ctx: PyContext,

diff --git a/wasm/Cargo.toml b/wasm/Cargo.toml
@@ -15,6 +15,10 @@ rustpython_vm = {path = "../vm"}
 cfg-if = "0.1.2"
 wasm-bindgen = "0.2"
 
+[dependencies.web-sys]
+version = "0.3"
+features = [ "console" ]
+
 
 [profile.release]
 opt-level = "s"
diff --git a/wasm/src/lib.rs b/wasm/src/lib.rs
@@ -1,28 +1,34 @@
+mod wasm_builtins;
+
 extern crate rustpython_vm;
 extern crate wasm_bindgen;
-use rustpython_vm::compile;
+extern crate web_sys;
+
 use rustpython_vm::VirtualMachine;
+use rustpython_vm::compile;
+use rustpython_vm::pyobject::AttributeProtocol;
 use wasm_bindgen::prelude::*;
-
-#[wasm_bindgen]
-extern "C" {
-    // Use `js_namespace` here to bind `console.log(..)` instead of just
-    // `log(..)`
-    #[wasm_bindgen(js_namespace = console)]
-    fn log(s: &str);
-}
+use web_sys::console;
 
 #[wasm_bindgen]
 pub fn run_code(source: &str) -> () {
     //add hash in here
-    log("Running RustPython");
-    log(&source.to_string());
+    console::log_1(&"Running RustPython".into());
+    console::log_1(&"Running code:".into());
+    console::log_1(&source.to_string().into());
+    console::log_1(&"----- console -----".into());
+
     let mut vm = VirtualMachine::new();
+    // We are monkey-patching the builtin print to use console.log
+    // TODO: moneky-patch sys.stdout instead, after print actually uses sys.stdout
+    vm.builtins.set_attr("print", vm.context().new_rustfunc(wasm_builtins::builtin_print));
+
     let code_obj = compile::compile(&mut vm, &source.to_string(), compile::Mode::Exec, None);
+
     let builtins = vm.get_builtin_scope();
     let vars = vm.context().new_scope(Some(builtins));
     match vm.run_code_obj(code_obj.unwrap(), vars) {
-        Ok(_value) => log("Execution successful"),
-        Err(_) => log("Execution failed"),
+        Ok(_value) => console::log_1(&"Execution successful".into()),
+        Err(_) => console::log_1(&"Execution failed".into()),
     }
 }
diff --git a/wasm/src/wasm_builtins.rs b/wasm/src/wasm_builtins.rs
@@ -0,0 +1,28 @@
+//! Builtin function specific to WASM build.
+//!
+//! This is required because some feature like I/O works differently in the browser comparing to
+//! desktop.
+//! Implements functions listed here: https://docs.python.org/3/library/builtins.html
+//!
+extern crate wasm_bindgen;
+extern crate web_sys;
+
+use rustpython_vm::obj::objstr;
+use rustpython_vm::VirtualMachine;
+use rustpython_vm::pyobject::{ PyFuncArgs, PyResult };
+use web_sys::console;
+
+pub fn builtin_print(vm: &mut VirtualMachine, args: PyFuncArgs) -> PyResult {
+    let mut first = true;
+    for a in args.args {
+        if first {
+            first = false;
+        } else {
+            console::log_1(&" ".into())
+        }
+        let v = vm.to_str(&a)?;
+        let s = objstr::get_value(&v);
+        console::log_1(&format!("{}", s).into())
+    }
+    Ok(vm.get_none())
+}