Custom Demo Gen Functions

core/src/hir/attrs.rs

@@ -81,6 +81,16 @@ pub struct DemoInfo {
     /// `#[diplomat::demo(external)]` represents an item that we will not evaluate, and should be passed to the rendering engine to provide.
     pub external: bool,
 
+    /// `#[diplomat::demo(custom_func = "/file/name/here.mjs")]` can be used above any `struct` definition in the bridge. The linked `.mjs` should contain a JS definition of functions that should be bundled with demo_gen's output.
+    ///
+    /// We call these functions "custom functions", as they are JS functions that are not automagically generated by demo_gen, but rather included as part of its JS output in the `RenderInfo` object.
+    ///
+    /// For more information on custom functions (and their use), see the relevant chapter in [the book](https://rust-diplomat.github.io/book/demo_gen/custom_functions.html).
+    ///
+    /// Files are located relative to lib.rs.
+    ///
+    pub custom_func: Option<String>,
+
     /// `#[diplomat::demo(input(...))]` represents configuration options for anywhere we might expect user input.
     pub input_cfg: DemoInputCFG,
 }
@@ -405,11 +415,29 @@ impl Attrs {
                             }
                         })
                         .expect("Could not read input(...)");
+                } else if path_ident == "custom_func" {
+                    let v = &attr.meta.require_name_value().unwrap().value;
+
+                    if let syn::Expr::Lit(s) = v {
+                        if let syn::Lit::Str(string) = &s.lit {
+                            this.demo_attrs.custom_func = Some(string.value());
+                        } else {
+                            errors.push(LoweringError::Other(format!(
+                                "#[diplomat::demo(custom_func={s:?}) must be a literal string."
+                            )));
+                        }
+                    } else {
+                        errors.push(LoweringError::Other(format!(
+                            "#[diplomat::demo(custom_func={v:?}) must be a literal string."
+                        )));
+                    }
                 } else {
-                    panic!("Unknown demo_attr: {path_ident:?}");
+                    errors.push(LoweringError::Other(format!(
+                        "Unknown demo_attr: {path_ident:?}"
+                    )));
                 }
             } else {
-                panic!("Unknown demo_attr: {path:?}");
+                errors.push(LoweringError::Other(format!("Unknown demo_attr: {path:?}")));
             }
         }
 

core/src/hir/snapshots/diplomat_core__hir__elision__tests__elision_in_struct.snap

@@ -48,6 +48,7 @@ Method {
                     generate: false,
                     default_constructor: false,
                     external: false,
+                    custom_func: None,
                     input_cfg: DemoInputCFG {
                         label: "",
                         default_value: "",
@@ -100,6 +101,7 @@ Method {
                     generate: false,
                     default_constructor: false,
                     external: false,
+                    custom_func: None,
                     input_cfg: DemoInputCFG {
                         label: "",
                         default_value: "",
@@ -125,6 +127,7 @@ Method {
             generate: false,
             default_constructor: false,
             external: false,
+            custom_func: None,
             input_cfg: DemoInputCFG {
                 label: "",
                 default_value: "",

core/src/hir/snapshots/diplomat_core__hir__elision__tests__simple_mod.snap

@@ -51,6 +51,7 @@ TypeContext {
                             generate: false,
                             default_constructor: false,
                             external: false,
+                            custom_func: None,
                             input_cfg: DemoInputCFG {
                                 label: "",
                                 default_value: "",
@@ -107,6 +108,7 @@ TypeContext {
                                     generate: false,
                                     default_constructor: false,
                                     external: false,
+                                    custom_func: None,
                                     input_cfg: DemoInputCFG {
                                         label: "",
                                         default_value: "",
@@ -151,6 +153,7 @@ TypeContext {
                             generate: false,
                             default_constructor: false,
                             external: false,
+                            custom_func: None,
                             input_cfg: DemoInputCFG {
                                 label: "",
                                 default_value: "",
@@ -173,6 +176,7 @@ TypeContext {
                     generate: false,
                     default_constructor: false,
                     external: false,
+                    custom_func: None,
                     input_cfg: DemoInputCFG {
                         label: "",
                         default_value: "",
@@ -236,6 +240,7 @@ TypeContext {
                             generate: false,
                             default_constructor: false,
                             external: false,
+                            custom_func: None,
                             input_cfg: DemoInputCFG {
                                 label: "",
                                 default_value: "",
@@ -294,6 +299,7 @@ TypeContext {
                                     generate: false,
                                     default_constructor: false,
                                     external: false,
+                                    custom_func: None,
                                     input_cfg: DemoInputCFG {
                                         label: "",
                                         default_value: "",
@@ -331,6 +337,7 @@ TypeContext {
                                     generate: false,
                                     default_constructor: false,
                                     external: false,
+                                    custom_func: None,
                                     input_cfg: DemoInputCFG {
                                         label: "",
                                         default_value: "",
@@ -369,6 +376,7 @@ TypeContext {
                             generate: false,
                             default_constructor: false,
                             external: false,
+                            custom_func: None,
                             input_cfg: DemoInputCFG {
                                 label: "",
                                 default_value: "",
@@ -391,6 +399,7 @@ TypeContext {
                     generate: false,
                     default_constructor: false,
                     external: false,
+                    custom_func: None,
                     input_cfg: DemoInputCFG {
                         label: "",
                         default_value: "",
@@ -436,6 +445,7 @@ TypeContext {
                     generate: false,
                     default_constructor: false,
                     external: false,
+                    custom_func: None,
                     input_cfg: DemoInputCFG {
                         label: "",
                         default_value: "",

example/demo_gen/custom_func/a.mjs

@@ -0,0 +1,20 @@
+import { lib } from "./index.mjs";
+
+export function multiplyPow10(power) {
+	let fixedDecimal = lib.FixedDecimal.new_(10);
+	fixedDecimal.multiplyPow10(power);
+	return fixedDecimal.toString();
+}
+
+export default {
+	"FixedDecimal.multiplyPow10": {
+		func: multiplyPow10,
+		funcName: "FixedDecimal.multiplyPow10",
+		parameters: [
+			{
+				name: "power",
+				type: "number"
+			}
+		]
+	}
+};

example/demo_gen/test/test-demo.mjs

@@ -1,5 +1,5 @@
 import test from "ava";
-import { FixedDecimalDemo, FixedDecimalFormatterDemo } from "mini-icu4x-demo";
+import { FixedDecimalDemo, FixedDecimalFormatterDemo, RenderInfo } from "mini-icu4x-demo";
 import { FixedDecimalGroupingStrategy } from "mini-icu4x";
 
 
@@ -9,4 +9,8 @@ test("Test FixedDecimal", (t) => {
 
 test("Test FixedDecimalFormatter", (t) => {
 	t.is(FixedDecimalFormatterDemo.formatWrite("en", FixedDecimalGroupingStrategy.Always, false, 1000), "1,000");
+});
+
+test("Custom Function", (t) => {
+	t.is(RenderInfo.termini["FixedDecimal.multiplyPow10"].func(3), "10000");
 });

example/src/fixed_decimal.rs

@@ -7,6 +7,9 @@ pub mod ffi {
 
     #[diplomat::opaque]
     #[diplomat::rust_link(fixed_decimal::FixedDecimal, Struct)]
+    // Link to where other custom functions for this class can be found.
+    // Make sure any .mjs file export defaults an object that matches the `RenderTerminus.terminus` object in content.
+    #[diplomat::demo(custom_func = "../demo_gen/custom_func/a.mjs")]
     pub struct FixedDecimal(pub fixed_decimal::FixedDecimal);
 
     impl FixedDecimal {