initial work for compile-time evaluation (vercel/turborepo#3495)

Allows to skip unreachable code based on compile-time constant
conditions

e. g.

```
if (!process.turbopack) {
  require("will-not-be-processed");
}
```

* add if() and process.turbopack fixes WEB-491
* Removes unreachable code fixes WEB-498
* evaluate some logical operations `&&`, `||`, `??`, `!`
* fix arguments handling fixes WEB-529
* nested effects for function called with closures
* handle closures when array methods are used fixes WEB-538
* evaluates `process.turbopack` fixes WEB-496

Author: sokra

crates/next-dev-tests/tests/integration/turbopack/basic/comptime/input/index.js

@@ -0,0 +1,82 @@
+it("importing a not existing file should throw", () => {
+  // This is a check to make sure that the following tests would fail if they require("fail")
+  expect(() => {
+    require("./not-existing-file");
+  }).toThrow();
+});
+
+function maybeReturn(x) {
+  if (x) {
+    return true;
+  }
+}
+
+function func() {
+  if (false) {
+    require("fail");
+    import("fail");
+  }
+  if (true) {
+    require("./ok");
+  }
+  if (true) {
+    require("./ok");
+  } else {
+    require("fail");
+    import("fail");
+  }
+  if (false) {
+    require("fail");
+    import("fail");
+  } else {
+    require("./ok");
+  }
+}
+
+it("should not follow conditional references", () => {
+  func();
+
+  expect(func.toString()).not.toContain("import(");
+});
+
+it("should allow replacements in IIFEs", () => {
+  (function func() {
+    if (false) {
+      require("fail");
+      import("fail");
+    }
+  })();
+});
+
+it("should support functions that only sometimes return", () => {
+  let ok = false;
+  if (maybeReturn(true)) {
+    ok = true;
+  }
+  expect(ok).toBe(true);
+});
+
+it("should evaluate process.turbopack", () => {
+  let ok = false;
+  if (process.turbopack) {
+    ok = true;
+  } else {
+    require("fail");
+    import("fail");
+  }
+  expect(ok).toBe(true);
+});
+
+it("should evaluate !process.turbopack", () => {
+  if (!process.turbopack) {
+    require("fail");
+    import("fail");
+  }
+});
+
+// it("should evaluate NODE_ENV", () => {
+//   if (process.env.NODE_ENV !== "development") {
+//     require("fail");
+//     import("fail");
+//   }
+// });

crates/next-dev-tests/tests/integration/turbopack/basic/comptime/input/ok.js

@@ -1,6 +1,6 @@
 use std::fmt::Display;
 
-// These enums list well known types, which we use internally. Plugins might add
+// These enums list well-known types, which we use internally. Plugins might add
 // custom types too.
 
 // TODO when plugins are supported, replace u8 with a trait that defines the

crates/turbopack-core/src/reference_type.rs

@@ -141,7 +141,7 @@ impl TestAppBuilder {
                     };
 
                     #[cfg(windows)]
-                    let relative_effect = relative_effect.replace("\\", "/");
+                    let relative_effect = relative_effect.replace('\\', "/");
 
                     formatdoc! {r#"
                         {SETUP_IMPORTS}

crates/turbopack-create-test-app/src/test_app_builder.rs

@@ -76,7 +76,7 @@ pub async fn process_request_with_content_source(
 
                 let header_map = response.headers_mut().expect("headers must be defined");
 
-                for (header_name, header_value) in &*headers {
+                for (header_name, header_value) in headers {
                     header_map.append(
                         HeaderName::try_from(header_name.clone())?,
                         hyper::header::HeaderValue::try_from(header_value.as_str())?,

crates/turbopack-dev-server/src/http.rs

@@ -56,11 +56,11 @@ pub async fn resolve_source_request(
             ContentSourceResult::NeedData(needed) => {
                 current_source = needed.source.resolve().await?;
                 current_asset_path = needed.path.clone();
-                data = request_to_data(&mut request_overwrites, &needed.vary).await?;
+                data = request_to_data(&request_overwrites, &needed.vary).await?;
             }
             ContentSourceResult::Result { get_content, .. } => {
                 let content_vary = get_content.vary().await?;
-                let content_data = request_to_data(&mut request_overwrites, &content_vary).await?;
+                let content_data = request_to_data(&request_overwrites, &content_vary).await?;
                 let content = get_content.get(Value::new(content_data));
                 match &*content.await? {
                     ContentSourceContent::Rewrite(rewrite) => {

crates/turbopack-dev-server/src/source/resolve.rs

@@ -20,7 +20,10 @@ lazy_static = "1.4.0"
 next-font = { path = "../next-font" }
 next-transform-dynamic = { path = "../next-transform-dynamic" }
 next-transform-strip-page-exports = { path = "../next-transform-strip-page-exports" }
+num-bigint = "0.4"
+num-traits = "0.2.15"
 once_cell = "1.13.0"
+parking_lot = "0.12.1"
 pin-project-lite = "0.2.9"
 regex = "1.5.4"
 serde = "1.0.136"
@@ -58,9 +61,6 @@ swc_core = { workspace = true, features = [
   "base",
 ] }
 
-  [dependencies.num-bigint]
-  version = "0.4"
-
 [dev-dependencies]
 criterion = { version = "0.3.5", features = ["async_tokio"] }
 rstest = "0.12.0"

crates/turbopack-ecmascript/Cargo.toml

@@ -1,9 +1,4 @@
-use std::{
-    fs,
-    path::PathBuf,
-    sync::{Arc, Mutex},
-    time::Duration,
-};
+use std::{fs, path::PathBuf, sync::Arc, time::Duration};
 
 use criterion::{Bencher, BenchmarkId, Criterion};
 use swc_core::{
@@ -23,8 +18,8 @@ use turbopack_core::{
 };
 use turbopack_ecmascript::analyzer::{
     graph::{create_graph, EvalContext, VarGraph},
-    linker::{link, LinkCache},
-    test_utils::visitor,
+    linker::link,
+    test_utils::{early_visitor, visitor},
 };
 
 pub fn benchmark(c: &mut Criterion) {
@@ -95,28 +90,24 @@ fn bench_link(b: &mut Bencher, input: &BenchInput) {
         .unwrap();
 
     b.to_async(rt).iter(|| async {
-        let cache = Mutex::new(LinkCache::new());
         for val in input.var_graph.values.values() {
             VcStorage::with(async {
+                let env = EnvironmentVc::new(
+                    Value::new(ExecutionEnvironment::NodeJsLambda(
+                        NodeJsEnvironment {
+                            compile_target: CompileTargetVc::unknown(),
+                            ..Default::default()
+                        }
+                        .into(),
+                    )),
+                    Value::new(EnvironmentIntention::ServerRendering),
+                );
                 link(
                     &input.var_graph,
                     val.clone(),
-                    &(|val| {
-                        Box::pin(visitor(
-                            val,
-                            EnvironmentVc::new(
-                                Value::new(ExecutionEnvironment::NodeJsLambda(
-                                    NodeJsEnvironment {
-                                        compile_target: CompileTargetVc::unknown(),
-                                        ..Default::default()
-                                    }
-                                    .into(),
-                                )),
-                                Value::new(EnvironmentIntention::ServerRendering),
-                            ),
-                        ))
-                    }),
-                    &cache,
+                    &early_visitor,
+                    &(|val| visitor(val, env)),
+                    Default::default(),
                 )
                 .await
             })