add transform callback to options so that tooling authors can customize the transform and still have correct parse / process results without a bunch of index math / conversions

index.html

@@ -8,7 +8,15 @@
     import {Preprocessor} from 'content-tag';
 
     const p = new Preprocessor();
-    const output = p.process('<template>Hi from createPreprocessor</template>');
+    const output = p.process(`
+      <template>
+        Hello World, from Vite!
+      </template>
+    `, {
+      transform: (src, type) => {
+        return `hi: ${type} src: ${src}`;
+      }
+    });
 
     document.querySelector('#output').innerHTML = output;
   </script>

src/bindings.rs

@@ -38,17 +38,28 @@ impl Options {
                 None
             };
 
+            let option_transform = Reflect::get(&options, &"transform".into()).unwrap();
+            // NOTE: That this will be None if this value was passed but not as a valid transform
+            // We probably want to error here.
+            let transform = option_transform.dyn_into::<js_sys::Function>().ok();
+            // transform
+            //     .call1(&JsValue::NULL, &JsValue::from("hi"))
+            //     .unwrap();
+
             Self {
                 // unwrap is justified here for the same reasons as commented above
                 inline_source_map: js_boolean(
                     &Reflect::get(&options, &"inline_source_map".into()).unwrap(),
                 ),
                 filename,
+                transform,
             }
         } else {
             Self {
                 inline_source_map: false,
                 filename: None,
+                // transform: Default?
+                transform: None,
             }
         }
     }

src/lib.rs

@@ -7,11 +7,11 @@ use base64::{engine::general_purpose, Engine as _};
 use std::path::PathBuf;
 use swc_common::comments::SingleThreadedComments;
 use swc_common::source_map::SourceMapGenConfig;
-use swc_common::{self, sync::Lrc, FileName, SourceMap, Mark};
+use swc_common::{self, sync::Lrc, FileName, Mark, SourceMap};
 use swc_core::common::GLOBALS;
 use swc_ecma_ast::{
-    Ident, ImportDecl, ImportNamedSpecifier, ImportSpecifier, Module, ModuleDecl,
-    ModuleExportName, ModuleItem,
+    Ident, ImportDecl, ImportNamedSpecifier, ImportSpecifier, Module, ModuleDecl, ModuleExportName,
+    ModuleItem,
 };
 use swc_ecma_codegen::Emitter;
 use swc_ecma_parser::{lexer::Lexer, Parser, StringInput, Syntax, TsConfig};
@@ -21,14 +21,15 @@ use swc_ecma_utils::private_ident;
 use swc_ecma_visit::{as_folder, VisitMutWith, VisitWith};
 
 mod bindings;
+mod locate;
 mod snippets;
 mod transform;
-mod locate;
 
 #[derive(Default)]
 pub struct Options {
     pub filename: Option<PathBuf>,
     pub inline_source_map: bool,
+    pub transform: Option<js_sys::Function>,
 }
 
 pub struct Preprocessor {
@@ -47,7 +48,6 @@ impl SourceMapGenConfig for SourceMapConfig {
     }
 }
 
-
 impl Preprocessor {
     pub fn new() -> Self {
         Self {
@@ -123,6 +123,7 @@ impl Preprocessor {
             parsed_module.visit_mut_with(&mut as_folder(transform::TransformVisitor::new(
                 &id,
                 Some(&mut needs_import),
+                options.transform,
             )));
 
             if !had_id_already && needs_import {
@@ -281,12 +282,9 @@ fn simplify_imports(parsed_module: &mut Module) {
     }
 }
 
-
-
 #[cfg(test)]
 mod test_helpers;
 
-
 macro_rules! testcase {
     ($test_name:ident, $input:expr, $expected:expr) => {
         #[test]

src/main.rs

@@ -23,6 +23,7 @@ fn main() {
         Options {
             filename: Some(filename),
             inline_source_map: true,
+            transform: None,
         },
     );
 

src/transform.rs

@@ -17,13 +17,19 @@ use swc_atoms::Atom;
 pub struct TransformVisitor<'a> {
     template_identifier: Ident,
     found_it: Option<&'a mut bool>,
+    transform: Option<js_sys::Function>,
 }
 
 impl<'a> TransformVisitor<'a> {
-    pub fn new(id: &Ident, found_it: Option<&'a mut bool>) -> Self {
+    pub fn new(
+        id: &Ident,
+        found_it: Option<&'a mut bool>,
+        transform: Option<js_sys::Function>,
+    ) -> Self {
         TransformVisitor {
             template_identifier: id.clone(),
             found_it,
+            transform,
         }
     }
     fn set_found_it(&mut self) {
@@ -40,6 +46,22 @@ impl<'a> TransformVisitor<'a> {
             ..
         } = expr;
 
+        // Replace the entirety of the <template>...</template> expression
+        // with the results of the transform call
+        if let Some(transform) = self.transform.as_ref() {
+            let content = transform
+                .call2(
+                    &wasm_bindgen::JsValue::NULL,
+                    &wasm_bindgen::JsValue::from(&contents.value.to_string()),
+                    &wasm_bindgen::JsValue::from("expression"),
+                    /* utils ( for bindImport )*/
+                )
+                .unwrap();
+
+            // TODO: error if content is not a string
+            return Expr::Lit(content.as_string().unwrap().into());
+        }
+
         Expr::Call(CallExpr {
             span: *span,
             callee: Callee::Expr(Box::new(Expr::Ident(self.template_identifier.clone()))),
@@ -67,7 +89,11 @@ impl<'a> TransformVisitor<'a> {
 }
 
 fn escape_template_literal(input: &Atom) -> Atom {
-    input.replace("\\", "\\\\").replace("`", "\\`").replace("$", "\\$").into()
+    input
+        .replace("\\", "\\\\")
+        .replace("`", "\\`")
+        .replace("$", "\\$")
+        .into()
 }
 
 impl<'a> VisitMut for TransformVisitor<'a> {
@@ -154,6 +180,7 @@ test!(
         as_folder(TransformVisitor::new(
             &Ident::new("template".into(), Default::default()),
             None,
+            None,
         ))
     },
     content_tag_template_expression,
@@ -166,6 +193,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     content_tag_template_member,
     r#"class X { <template>Hello</template> } "#,
@@ -181,6 +209,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     expression_inside_class_member,
     r#"class X { thing = <template>Hello</template> } "#,
@@ -194,6 +223,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     class_member_inside_expression,
     r#"let x = class { <template>Hello</template> } "#,
@@ -209,6 +239,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     content_tag_export_default,
     r#"<template>Hello</template>"#,
@@ -220,6 +251,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     inner_expression,
     r#"let x = doIt(<template>Hello</template>)"#,
@@ -231,6 +263,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     backtick_in_template,
     r#"let x = <template>He`llo</template>"#,
@@ -242,6 +275,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     dollar_in_template,
     r#"let x = <template>He${ll}o</template>"#,
@@ -253,6 +287,7 @@ test!(
     |_| as_folder(TransformVisitor::new(
         &Ident::new("template".into(), Default::default()),
         None,
+        None,
     )),
     do_not_interpret_js_escapes_in_hbs,
     r#"let x = <template>Hello\nWorld\u1234</template>"#,

test/parse.test.js

@@ -173,7 +173,7 @@ describe(`parse`, function () {
       p.process(
         `const thing = "face";
   <template>Hi`,
-        { filename: 'path/to/my/component.gjs' }
+        { filename: "path/to/my/component.gjs" }
       );
     }).to.throw(`Parse Error at path/to/my/component.gjs:2:15: 2:15`);
   });

test/process.test.js

@@ -9,6 +9,35 @@ const { expect } = chai;
 const p = new Preprocessor();
 
 describe(`process`, function () {
+  it("tmp", function () {
+    let output = p.process("<template>Hi</template>", {
+      transform: (src, type, utils) => {
+        console.log("Did it run?");
+        let t = "todo";
+        // let t = utils.bindImport("@ember/template-compiler", "template");
+
+        if (type === "expression") {
+          return `${t}("${utils.escapeStringLiteral(
+            src
+          )}", { eval() { console.log("hi"); return eval(arguments[0]) } }`;
+        } else {
+          return `static {
+            ${t}("${utils.escapeStringLiteral(src)}", {
+              eval() { return eval(arguments[0]) },
+              component: this,
+            })
+          }`;
+        }
+      },
+    });
+
+    expect(output).to
+      .equalCode(`import { template } from "@ember/template-compiler";
+  export default template(\`Hi\`, {
+      eval () { console.log("hi"); return eval(arguments[0]) }
+  });`);
+  });
+
   it("works for a basic example", function () {
     let output = p.process("<template>Hi</template>");
 
@@ -91,7 +120,9 @@ describe(`process`, function () {
   });
 
   it("Provides inline source maps if inline_source_map option is set to true", function () {
-    let output = p.process(`<template>Hi</template>`, { inline_source_map: true });
+    let output = p.process(`<template>Hi</template>`, {
+      inline_source_map: true,
+    });
 
     expect(output).to.match(
       /sourceMappingURL=data:application\/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbIjxhbm9uPiJdLCJzb3VyY2VzQ29udGVudCI6WyI8dGVtcGxhdGU-SGk8L3RlbXBsYXRlPiJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiO0FBQUEsZUFBQSxTQUFVLENBQUEsRUFBRSxDQUFBLEVBQUE7SUFBQTtRQUFBLE9BQUEsS0FBQSxTQUFBLENBQUEsRUFBVztJQUFEO0FBQUEsR0FBQyJ9/