Merge pull request #2173 from aarroyoc/js-eval

Add js_eval/2 for wasm32

src/lib.rs

@@ -51,7 +51,8 @@ use wasm_bindgen::prelude::*;
 #[wasm_bindgen]
 pub fn eval_code(s: &str) -> String {
     use machine::mock_wam::*;
-    use web_sys::console;
+
+    console_error_panic_hook::set_once();
 
     let mut wam = Machine::with_test_streams();
     let bytes = wam.test_load_string(s);

src/lib/wasm.pl

@@ -0,0 +1,29 @@
+/** Predicates for the WebAssembly platform
+
+This module contains predicates that are only available in
+the WASM (WebAssembly) version of Scryer Prolog.
+*/
+
+:- module(wasm, [js_eval/2]).
+
+:- use_module(library(error)).
+
+%% js_eval(+JsCode, -Result).
+%
+% Executes a JavaScript snippet `JsCode` using the platform
+% `eval` function. `Result` takes the return value of that code.
+% Strings, booleans, numbers, null and undefined are directly mapped to Prolog.
+% Arrays, objects, bigints, symbols and functions are not mapped.
+% Instead, a `js_{type}` atom will be returned.
+%
+% Example (on a browser):
+%
+% ```
+% ?- js_eval("prompt('What is your name?')", Name).
+%    % A prompt is showed, with a textbox.
+%    Name = "Whatever was written on the textbox".
+% ```
+js_eval(JsCode, Result) :-
+    must_be(chars, JsCode),
+    can_be(chars, Result),
+    '$js_eval'(JsCode, Result).

src/machine/dispatch.rs

@@ -4139,6 +4139,14 @@ impl Machine {
                         try_or_throw!(self.machine_st, self.define_foreign_struct());
                         step_or_fail!(self, self.machine_st.p = self.machine_st.cp);
                     }
+                    &Instruction::CallJsEval => {
+                        try_or_throw!(self.machine_st, self.js_eval());
+                        step_or_fail!(self, self.machine_st.p += 1);
+                    }
+                    &Instruction::ExecuteJsEval => {
+                        try_or_throw!(self.machine_st, self.js_eval());
+                        step_or_fail!(self, self.machine_st.p = self.machine_st.cp);
+                    }
                     &Instruction::CallCurrentTime => {
                         self.current_time();
                         step_or_fail!(self, self.machine_st.p += 1);

src/machine/system_calls.rs

@@ -4882,6 +4882,70 @@ impl Machine {
         Ok(())
     }
 
+    #[cfg(not(target_arch = "wasm32"))]
+    #[inline(always)]
+    pub(crate) fn js_eval(&mut self) -> CallResult {
+        unimplemented!()
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    #[inline(always)]
+    pub(crate) fn js_eval(&mut self) -> CallResult {
+        let code = self.deref_register(1);
+        let result_reg = self.deref_register(2);
+        if let Some(code) = self.machine_st.value_to_str_like(code) {
+            let result = match js_sys::eval(&code.as_str()) {
+                Ok(result) => self.unify_js_value(result, result_reg),
+                Err(result) => self.unify_js_value(result, result_reg),
+            };
+            return Ok(());
+        }
+        self.machine_st.fail = true;
+        Ok(())
+    }
+
+    #[cfg(target_arch = "wasm32")]
+    fn unify_js_value(&mut self, result: wasm_bindgen::JsValue, result_reg: HeapCellValue) {
+        match result.as_bool() {
+            Some(result) => match result {
+                true => self.machine_st.unify_atom(atom!("true"), result_reg),
+                false => self.machine_st.unify_atom(atom!("false"), result_reg),
+            },
+            None => match result.as_f64() {
+                Some(result) => {
+                    let n = float_alloc!(result, self.machine_st.arena);
+                    self.machine_st.unify_f64(n, result_reg);
+                }
+                None => match result.as_string() {
+                    Some(result) => {
+                        let result = AtomTable::build_with(&self.machine_st.atom_tbl, &result);
+                        self.machine_st.unify_complete_string(result, result_reg);
+                    }
+                    None => {
+                        if result.is_null() {
+                            self.machine_st.unify_atom(atom!("null"), result_reg);
+                        } else if result.is_undefined() {
+                            self.machine_st.unify_atom(atom!("undefined"), result_reg);
+                        } else if result.is_symbol() {
+                            self.machine_st.unify_atom(atom!("js_symbol"), result_reg);
+                        } else if result.is_object() {
+                            self.machine_st.unify_atom(atom!("js_object"), result_reg);
+                        } else if result.is_array() {
+                            self.machine_st.unify_atom(atom!("js_array"), result_reg);
+                        } else if result.is_function() {
+                            self.machine_st.unify_atom(atom!("js_function"), result_reg);
+                        } else if result.is_bigint() {
+                            self.machine_st.unify_atom(atom!("js_bigint"), result_reg);
+                        } else {
+                            self.machine_st
+                                .unify_atom(atom!("js_unknown_type"), result_reg);
+                        }
+                    }
+                },
+            },
+        }
+    }
+
     #[inline(always)]
     pub(crate) fn current_time(&mut self) {
         let timestamp = self.systemtime_to_timestamp(SystemTime::now());