feat: vendor asserts from Deno stdlib

Allow modules to import
https://deno.land/std@0.177.0/testing/asserts.ts

This is a temporary workaround until we implement proper support for
ES modules, see #43.

Signed-off-by: Miroslav Bajtoš <oss@bajtos.net>

runtime/runtime.rs

@@ -153,22 +153,28 @@ impl ModuleLoader for ZinniaModuleLoader {
         ));
       }
 
-      if !specifier
-        .as_str()
-        .eq_ignore_ascii_case(main_js_module.as_str())
-      {
-        let mut msg =
-          "Zinnia does not support importing from other modules yet. "
-            .to_string();
-        msg.push_str(specifier.as_str());
-        if let Some(referrer) = &maybe_referrer {
-          msg.push_str(" imported from ");
-          msg.push_str(referrer.as_str());
+      let spec_str = specifier.as_str();
+
+      let code = {
+        if spec_str.eq_ignore_ascii_case(main_js_module.as_str()) {
+          read_file_to_string(specifier.to_file_path().unwrap()).await?
+        } else if spec_str == "https://deno.land/std@0.177.0/testing/asserts.ts"
+        {
+          // Temporary workaround until we implement ES Modules
+          // https://github.com/filecoin-station/zinnia/issues/43
+          include_str!("./vendored/asserts.bundle.js").to_string()
+        } else {
+          let mut msg =
+            "Zinnia does not support importing from other modules yet. "
+              .to_string();
+          msg.push_str(specifier.as_str());
+          if let Some(referrer) = &maybe_referrer {
+            msg.push_str(" imported from ");
+            msg.push_str(referrer.as_str());
+          }
+          return Err(anyhow!(msg));
         }
-        return Err(anyhow!(msg));
-      }
-
-      let code = read_file_to_string(specifier.to_file_path().unwrap()).await?;
+      };
 
       let module = ModuleSource {
         code: Box::from(code.as_bytes()),

runtime/vendor.js

@@ -0,0 +1,28 @@
+// Run this Deno script to fetch and store Deno modules
+// This is a temporary workaround until we support module imports
+// See https://github.com/filecoin-station/zinnia/issues/43
+//
+// Run this script using the following command:
+//   deno --allow-all runtime/vendor.js
+
+import { fromFileUrl } from "https://deno.land/std@0.177.0/path/mod.ts";
+
+await vendor(
+  "https://deno.land/std@0.177.0/testing/asserts.ts",
+  "asserts.bundle.js",
+);
+
+async function vendor(url, outfile) {
+  const outpath = fromFileUrl(import.meta.resolve(`./vendored/${outfile}`));
+  const cmd = ["deno", "bundle", url, "--", outpath];
+  const child = Deno.run({ cmd });
+  const status = await child.status();
+  child.close();
+  if (!status.success) {
+    const reason = status.code
+      ? `code ${status.code}`
+      : `signal ${status.signal}`;
+
+    throw new Error(`Process failed with ${reason}: ${cmd}`);
+  }
+}