Reflect optional struct fields in typescript (#1990)

* reflect option struct fields in typescript

* optional fields: move type checker to getter

* infer optional fields from ts_args

crates/cli-support/src/js/binding.rs

@@ -64,6 +64,7 @@ pub struct JsFunction {
     pub js_doc: String,
     pub ts_arg_tys: Vec<String>,
     pub ts_ret_ty: Option<String>,
+    pub might_be_optional_field: bool,
 }
 
 impl<'a, 'b> Builder<'a, 'b> {
@@ -215,16 +216,25 @@ impl<'a, 'b> Builder<'a, 'b> {
         code.push_str(&call);
         code.push_str("}");
 
-        let (ts_sig, ts_arg_tys, ts_ret_ty) =
-            self.typescript_signature(&function_args, &arg_tys, &adapter.results);
+        // Rust Structs' fields converted into Getter and Setter functions before
+        // we decode them from webassembly, finding if a function is a field
+        // should start from here. Struct fields(Getter) only have one arg, and
+        // this is the clue we can infer if a function might be a field.
+        let mut might_be_optional_field = false;
+        let (ts_sig, ts_arg_tys, ts_ret_ty) = self.typescript_signature(
+            &function_args,
+            &arg_tys,
+            &adapter.results,
+            &mut might_be_optional_field,
+        );
         let js_doc = self.js_doc_comments(&function_args, &arg_tys, &ts_ret_ty);
-
         Ok(JsFunction {
             code,
             ts_sig,
             js_doc,
             ts_arg_tys,
             ts_ret_ty,
+            might_be_optional_field,
         })
     }
 
@@ -238,6 +248,7 @@ impl<'a, 'b> Builder<'a, 'b> {
         arg_names: &[String],
         arg_tys: &[&AdapterType],
         result_tys: &[AdapterType],
+        might_be_optional_field: &mut bool,
     ) -> (String, Vec<String>, Option<String>) {
         // Build up the typescript signature as well
         let mut omittable = true;
@@ -270,6 +281,12 @@ impl<'a, 'b> Builder<'a, 'b> {
         ts_arg_tys.reverse();
         let mut ts = format!("({})", ts_args.join(", "));
 
+        // If this function is an optional field's setter, it should have only
+        // one arg, and omittable should be `true`.
+        if ts_args.len() == 1 && omittable {
+            *might_be_optional_field = true;
+        }
+
         // Constructors have no listed return type in typescript
         let mut ts_ret = None;
         if self.constructor.is_none() {

crates/cli-support/src/js/mod.rs

@@ -67,7 +67,8 @@ pub struct ExportedClass {
     /// All readable properties of the class
     readable_properties: Vec<String>,
     /// Map from field name to type as a string plus whether it has a setter
-    typescript_fields: HashMap<String, (String, bool)>,
+    /// and it is optional
+    typescript_fields: HashMap<String, (String, bool, bool)>,
 }
 
 const INITIAL_HEAP_VALUES: &[&str] = &["undefined", "null", "true", "false"];
@@ -703,14 +704,18 @@ impl<'a> Context<'a> {
         let mut fields = class.typescript_fields.keys().collect::<Vec<_>>();
         fields.sort(); // make sure we have deterministic output
         for name in fields {
-            let (ty, has_setter) = &class.typescript_fields[name];
+            let (ty, has_setter, is_optional) = &class.typescript_fields[name];
             ts_dst.push_str("  ");
             if !has_setter {
                 ts_dst.push_str("readonly ");
             }
             ts_dst.push_str(name);
-            ts_dst.push_str(": ");
-            ts_dst.push_str(ty);
+            if *is_optional {
+                ts_dst.push_str("?: ");
+            } else {
+                ts_dst.push_str(": ");
+            }
+            ts_dst.push_str(&ty);
             ts_dst.push_str(";\n");
         }
         dst.push_str("}\n");
@@ -781,9 +786,7 @@ impl<'a> Context<'a> {
         if !self.should_write_global("not_defined") {
             return;
         }
-        self.global(
-            "function notDefined(what) { return () => { throw new Error(`${what} is not defined`); }; }"
-        );
+        self.global("function notDefined(what) { return () => { throw new Error(`${what} is not defined`); }; }");
     }
 
     fn expose_assert_num(&mut self) {
@@ -2045,6 +2048,7 @@ impl<'a> Context<'a> {
             ts_ret_ty,
             js_doc,
             code,
+            might_be_optional_field,
         } = builder
             .process(&adapter, instrs, arg_names)
             .with_context(|| match kind {
@@ -2089,7 +2093,7 @@ impl<'a> Context<'a> {
                     AuxExportKind::Setter { class, field } => {
                         let arg_ty = ts_arg_tys[0].clone();
                         let exported = require_class(&mut self.exported_classes, class);
-                        exported.push_setter(&docs, field, &code, &arg_ty);
+                        exported.push_setter(&docs, field, &code, &arg_ty, might_be_optional_field);
                     }
                     AuxExportKind::StaticFunction { class, name } => {
                         let exported = require_class(&mut self.exported_classes, class);
@@ -3097,9 +3101,17 @@ impl ExportedClass {
 
     /// Used for adding a setter to a class, mainly to ensure that TypeScript
     /// generation is handled specially.
-    fn push_setter(&mut self, docs: &str, field: &str, js: &str, ret_ty: &str) {
-        let has_setter = self.push_accessor(docs, field, js, "set ", ret_ty);
+    fn push_setter(
+        &mut self,
+        docs: &str,
+        field: &str,
+        js: &str,
+        ret_ty: &str,
+        might_be_optional_field: bool,
+    ) {
+        let (has_setter, is_optional) = self.push_accessor(docs, field, js, "set ", ret_ty);
         *has_setter = true;
+        *is_optional = might_be_optional_field;
     }
 
     fn push_accessor(
@@ -3109,18 +3121,20 @@ impl ExportedClass {
         js: &str,
         prefix: &str,
         ret_ty: &str,
-    ) -> &mut bool {
+    ) -> (&mut bool, &mut bool) {
         self.contents.push_str(docs);
         self.contents.push_str(prefix);
         self.contents.push_str(field);
         self.contents.push_str(js);
         self.contents.push_str("\n");
-        let (ty, has_setter) = self
+
+        let (ty, has_setter, is_optional) = self
             .typescript_fields
             .entry(field.to_string())
             .or_insert_with(Default::default);
+
         *ty = ret_ty.to_string();
-        has_setter
+        (has_setter, is_optional)
     }
 }
 

crates/typescript-tests/src/lib.rs

@@ -1,5 +1,6 @@
 pub mod custom_section;
 pub mod getters_setters;
 pub mod opt_args_and_ret;
+pub mod optional_fields;
 pub mod simple_fn;
 pub mod simple_struct;

crates/typescript-tests/src/optional_fields.rs

@@ -0,0 +1,7 @@
+use wasm_bindgen::prelude::*;
+
+#[wasm_bindgen]
+pub struct Fields {
+    pub hallo: Option<bool>,
+    pub spaceboy: bool,
+}

crates/typescript-tests/src/optional_fields.ts

@@ -0,0 +1,3 @@
+import * as wbg from '../pkg/typescript_tests';
+
+const fields: wbg.Fields = { spaceboy: true, free: () => { } };

rustfmt.toml

@@ -0,0 +1 @@
+tab_spaces = 4