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resolver: don't let the main fallback clobber the module entry's sideEffects #36652

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resolver: don't let the main fallback clobber the module entry's sideEffects #36652

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6fefef4
resolver: don't let the main fallback clobber the module entry's side…
robobun Aug 1, 2026
36749d2
[autofix.ci] apply automated fixes
autofix-ci[bot] Aug 1, 2026
6d2172f
trim comments per review
robobun Aug 1, 2026
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49 changes: 23 additions & 26 deletions src/resolver/resolver.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1554,7 +1554,9 @@ impl<'a> Resolver<'a> {

let mut iter = result.path_pair.iter();
let mut module_type = result.module_type;
let mut is_primary_path = true;
while let Some(path) = iter.next() {
let is_primary = core::mem::replace(&mut is_primary_path, false);
let name = path.name();
let Ok(Some(dir)) = self.read_dir_info(name.dir) else {
continue;
Expand All @@ -1570,33 +1572,28 @@ impl<'a> Resolver<'a> {
PJSideEffects::Unspecified | PJSideEffects::Glob(_) | PJSideEffects::Mixed(_)
);

result.primary_side_effects_data = match &existing.side_effects {
PJSideEffects::Unspecified => SideEffects::HasSideEffects,
PJSideEffects::False => SideEffects::NoSideEffectsPackageJson,
PJSideEffects::Map(map) => {
if map.contains_key(&crate::package_json::StringHashMapUnownedKey::init(
path.text(),
)) {
SideEffects::HasSideEffects
} else {
SideEffects::NoSideEffectsPackageJson
}
}
PJSideEffects::Glob(_) => {
if existing.side_effects.has_side_effects(path.text()) {
SideEffects::HasSideEffects
} else {
SideEffects::NoSideEffectsPackageJson
if is_primary {
result.primary_side_effects_data = match &existing.side_effects {
PJSideEffects::Unspecified => SideEffects::HasSideEffects,
PJSideEffects::False => SideEffects::NoSideEffectsPackageJson,
PJSideEffects::Map(map) => {
if map.contains_key(
&crate::package_json::StringHashMapUnownedKey::init(path.text()),
) {
SideEffects::HasSideEffects
} else {
SideEffects::NoSideEffectsPackageJson
}
}
}
PJSideEffects::Mixed(_) => {
if existing.side_effects.has_side_effects(path.text()) {
SideEffects::HasSideEffects
} else {
SideEffects::NoSideEffectsPackageJson
PJSideEffects::Glob(_) | PJSideEffects::Mixed(_) => {
if existing.side_effects.has_side_effects(path.text()) {
SideEffects::HasSideEffects
} else {
SideEffects::NoSideEffectsPackageJson
}
}
}
};
};
}

if existing.name.is_empty() || self.care_about_bin_folder {
result.package_json = None;
Expand All @@ -1607,7 +1604,7 @@ impl<'a> Resolver<'a> {
.package_json
.or_else(|| dir.enclosing_package_json.map(std::ptr::from_ref));

if needs_side_effects {
if needs_side_effects && is_primary {
if let Some(package_json) = Result::deref_package_json(result.package_json) {
use crate::package_json::SideEffects as PJSideEffects;
result.primary_side_effects_data = match &package_json.side_effects {
Expand Down
88 changes: 88 additions & 0 deletions test/bundler/esbuild/dce.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -594,6 +594,94 @@ describe("bundler", () => {
stdout: "this should be kept\nunused import",
},
});
// https://github.com/oven-sh/bun/issues/8993
// The "name" field is load-bearing: without it the package is not recorded as the
// enclosing package.json and the secondary-path iteration is a no-op.
itBundled("dce/PackageJsonSideEffectsArrayModuleMainBareImport", {
todo: isWindows,
files: {
"/Users/user/project/src/entry.js": /* js */ `
import "demo-pkg"
console.log('after import')
`,
"/Users/user/project/node_modules/demo-pkg/dist/index-module.js": /* js */ `
import "./register.js"
export const foo = 1
`,
"/Users/user/project/node_modules/demo-pkg/dist/register.js": /* js */ `
console.log('this should be kept')
`,
"/Users/user/project/node_modules/demo-pkg/dist/index-main.js": /* js */ `
console.log('TEST FAILED')
`,
"/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
{
"name": "demo-pkg",
"main": "dist/index-main.js",
"module": "dist/index-module.js",
"sideEffects": ["./dist/index-module.js", "./dist/register.js"]
}
`,
},
dce: true,
run: {
stdout: "this should be kept\nafter import",
},
});
itBundled("dce/PackageJsonSideEffectsGlobModuleMainBareImport", {
todo: isWindows,
files: {
"/Users/user/project/src/entry.js": /* js */ `
import "demo-pkg"
console.log('after import')
`,
"/Users/user/project/node_modules/demo-pkg/dist/index-module.js": /* js */ `
console.log('this should be kept')
`,
"/Users/user/project/node_modules/demo-pkg/dist/bundle.node.js": /* js */ `
console.log('TEST FAILED')
`,
"/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
{
"name": "demo-pkg",
"main": "dist/bundle.node.js",
"module": "dist/index-module.js",
"sideEffects": ["./dist/index-*.js"]
}
`,
},
dce: true,
run: {
stdout: "this should be kept\nafter import",
},
});
itBundled("dce/PackageJsonSideEffectsArrayModuleMainBareImportRemove", {
files: {
"/Users/user/project/src/entry.js": /* js */ `
import "demo-pkg"
console.log('unused import')
`,
"/Users/user/project/node_modules/demo-pkg/dist/index-module.js": /* js */ `
export const foo = 'TEST FAILED'
console.log('TEST FAILED')
`,
"/Users/user/project/node_modules/demo-pkg/dist/index-main.js": /* js */ `
console.log('TEST FAILED')
`,
"/Users/user/project/node_modules/demo-pkg/package.json": /* json */ `
{
"name": "demo-pkg",
"main": "dist/index-main.js",
"module": "dist/index-module.js",
"sideEffects": ["./dist/index-main.js"]
}
`,
},
dce: true,
run: {
stdout: "unused import",
},
});
itBundled("dce/PackageJsonSideEffectsArrayGlob", {
files: {
"/Users/user/project/src/entry.js": /* js */ `
Expand Down
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