Turbopack: RawEcmascriptModule (#81806)

Add a JS module type that does no analysis, and just concatenates the source file into the output file.
As a consequence however, the input module cannot have
- `import`s/`require`s/`new Worker`/...
- ~~`process.env.*` that should be replaced~~
- JSX/any new syntax, since the module won't be transpiled using the user's browserslist

```
before:

 ✓ Starting...
 ✓ Ready in 335ms
 ○ Compiling / ...
 ✓ Compiled / in 980ms
 GET / 200 in 1258ms

after:

 ✓ Starting...
 ✓ Ready in 406ms
 ✓ Compiled / in 406ms
 GET / 200 in 692ms
```

<img width="1358" height="959" alt="Bildschirmfoto 2025-09-16 um 12 09 47" src="https://github.com/user-attachments/assets/87bb3161-8749-475b-9a84-bf62324735e4" />

<img width="1352" height="939" alt="Bildschirmfoto 2025-09-16 um 12 12 48" src="https://github.com/user-attachments/assets/4a42e724-7090-4ca7-bad9-41e5cf1af80b" />

Author: mischnic

Cargo.lock

@@ -35,6 +35,7 @@ remove_console = { workspace = true }
 itertools = { workspace = true }
 percent-encoding = "2.3.1"
 serde_path_to_error = { workspace = true }
+swc_sourcemap = { workspace = true }
 
 swc_core = { workspace = true, features = [
   "base",

crates/next-core/Cargo.toml

@@ -35,6 +35,7 @@ mod next_shared;
 pub mod next_telemetry;
 mod page_loader;
 pub mod pages_structure;
+pub mod raw_ecmascript_module;
 pub mod segment_config;
 pub mod tracing_presets;
 mod transform_options;

crates/next-core/src/lib.rs

@@ -2,7 +2,7 @@ use anyhow::Result;
 use next_custom_transforms::transforms::strip_page_exports::ExportFilter;
 use turbo_rcstr::RcStr;
 use turbo_tasks::{ResolvedVc, Vc};
-use turbopack::module_options::ModuleRule;
+use turbopack::module_options::{ModuleRule, ModuleRuleEffect, ModuleType, RuleCondition};
 
 use crate::{
     mode::NextMode,
@@ -17,6 +17,7 @@ use crate::{
         next_disallow_re_export_all_in_page::get_next_disallow_export_all_in_page_rule,
         next_pure::get_next_pure_rule, server_actions::ActionsTransform,
     },
+    raw_ecmascript_module::RawEcmascriptModuleType,
 };
 
 /// Returns a list of module rules which apply client-side, Next.js-specific
@@ -44,6 +45,20 @@ pub async fn get_next_client_transforms_rules(
         ));
     }
 
+    // This is purely a performance optimization:
+    // - The next-devtools file is very large and rather slow to analyze (unforatunately, at least
+    //   with our current implementation)
+    // - It's used by every single application in dev, even tiny (CNA) apps
+    // - It's prebundled already and doesn't contain any imports/requires
+    rules.push(ModuleRule::new(
+        RuleCondition::ResourcePathEndsWith(
+            "next/dist/compiled/next-devtools/index.js".to_string(),
+        ),
+        vec![ModuleRuleEffect::ModuleType(ModuleType::Custom(
+            ResolvedVc::upcast(RawEcmascriptModuleType {}.resolved_cell()),
+        ))],
+    ));
+
     rules.push(get_next_font_transform_rule(enable_mdx_rs));
 
     let is_development = mode.await?.is_development();

crates/next-core/src/next_client/transforms.rs

@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{Result, bail};
 use serde::{Deserialize, Serialize};
 use turbo_rcstr::rcstr;
 use turbo_tasks::{NonLocalValue, ResolvedVc, TaskInput, Vc, fxindexmap, trace::TraceRawVcs};
@@ -7,6 +7,7 @@ use turbopack_core::{
     context::AssetContext, module::Module, reference_type::ReferenceType, resolve::ModulePart,
     source::Source,
 };
+use turbopack_ecmascript::EcmascriptInputTransforms;
 use turbopack_static::ecma::StaticUrlJsModule;
 
 use super::source_asset::StructuredImageFileSource;
@@ -95,4 +96,14 @@ impl CustomModuleType for StructuredImageModuleType {
             module_asset_context,
         )
     }
+
+    #[turbo_tasks::function]
+    fn extend_ecmascript_transforms(
+        self: Vc<Self>,
+        _preprocess: Vc<EcmascriptInputTransforms>,
+        _main: Vc<EcmascriptInputTransforms>,
+        _postprocess: Vc<EcmascriptInputTransforms>,
+    ) -> Result<Vc<Box<dyn CustomModuleType>>> {
+        bail!("StructuredImageModuleType does not support adding Ecmascript transforms");
+    }
 }