fix: Handle the scenario where a package.json#browser field could be …

…`false` (#427)

We [recently shipped](#424) support
for the `browser` field, but we discovered an edge case where instead of
mapping to another string, the value could be `false` (eg,
[`object-inspect`](https://github.com/inspect-js/object-inspect/blob/main/package.json#L82)),
which indicates that this module should be treated as an empty object
(`{}`) (evidenced by its usage
[here](https://github.com/inspect-js/object-inspect/blob/main/index.js#L68-L70)).

The code was previously erroring on the string's `startsWith` checks,
causing the entire package to be omitted from the file mapping result.
This ensures that if the value is `false` we'll continue on.

---------

Co-authored-by: Steven <[email protected]>
Co-authored-by: kodiakhq[bot] <49736102+kodiakhq[bot]@users.noreply.github.com>

src/resolve-dependency.ts

@@ -128,7 +128,7 @@ interface PkgCfg {
   main: string | undefined;
   exports: PackageTarget;
   imports: { [key: string]: PackageTarget };
-  browser?: string | { [key: string]: string };
+  browser?: unknown;
 }
 
 async function getPkgCfg(
@@ -259,8 +259,18 @@ async function resolveRemappings(
 ): Promise<void> {
   if (job.conditions?.includes('browser')) {
     const { browser: pkgBrowser } = pkgCfg;
+    if (!pkgBrowser) {
+      return;
+    }
     if (typeof pkgBrowser === 'object') {
       for (const [key, value] of Object.entries(pkgBrowser)) {
+        if (typeof value !== 'string') {
+          /**
+           * `false` can be used to specify that a file is not meant to be included.
+           * Downstream processing is expected to handle this case, and it should remain in the mapping result
+           */
+          continue;
+        }
         if (!key.startsWith('./') || !value.startsWith('./')) {
           continue;
         }

test/unit/browser-remappings-false/.gitignore

@@ -0,0 +1,2 @@
+# include node_modules for testing
+!node_modules 

test/unit/browser-remappings-false/input.js

@@ -0,0 +1,2 @@
+require('pkg');
+

test/unit/browser-remappings-false/output.js

@@ -0,0 +1,7 @@
+[
+  "package.json",
+  "test/unit/browser-remappings-false/input.js",
+  "test/unit/browser-remappings-false/node_modules/pkg/browser.js",
+  "test/unit/browser-remappings-false/node_modules/pkg/index.js",
+  "test/unit/browser-remappings-false/node_modules/pkg/package.json"
+]

test/unit/browser-remappings-false/test-opts.json

@@ -0,0 +1,3 @@
+{
+  "conditions": ["browser"]
+}

test/unit/browser-remappings-string/.gitignore

@@ -0,0 +1,2 @@
+# include node_modules for testing
+!node_modules 

test/unit/browser-remappings-string/input.js

@@ -0,0 +1,2 @@
+require('pkg');
+

test/unit/browser-remappings-string/output.js

@@ -0,0 +1,7 @@
+[
+  "package.json",
+  "test/unit/browser-remappings-string/input.js",
+  "test/unit/browser-remappings-string/node_modules/pkg/browser.js",
+  "test/unit/browser-remappings-string/node_modules/pkg/index.js",
+  "test/unit/browser-remappings-string/node_modules/pkg/package.json"
+]

test/unit/browser-remappings-string/test-opts.json

@@ -0,0 +1,3 @@
+{
+  "conditions": ["browser"]
+}

test/unit/browser-remappings-undefined/.gitignore

@@ -0,0 +1,2 @@
+# include node_modules for testing
+!node_modules 

test/unit/browser-remappings-undefined/input.js

@@ -0,0 +1,2 @@
+require('pkg');
+

test/unit/browser-remappings-undefined/output.js

@@ -0,0 +1,9 @@
+[
+  "package.json",
+  "test/unit/browser-remappings-undefined/input.js",
+  "test/unit/browser-remappings-undefined/node_modules/pkg/index.js",
+  "test/unit/browser-remappings-undefined/node_modules/pkg/package.json",
+  "test/unit/browser-remappings-undefined/node_modules/pkg/require-main.cjs",
+  "test/unit/browser-remappings-undefined/node_modules/pkg/subdir/import-main.js",
+  "test/unit/browser-remappings-undefined/node_modules/pkg/subdir/package.json"
+]

test/unit/browser-remappings-undefined/test-opts.json

@@ -0,0 +1,3 @@
+{
+  "conditions": ["browser"]
+}

test/unit/browser-remappings/output.js

@@ -7,4 +7,4 @@
   "test/unit/browser-remappings/node_modules/pkg/subdir/import-main-browser.js",
   "test/unit/browser-remappings/node_modules/pkg/subdir/import-main.js",
   "test/unit/browser-remappings/node_modules/pkg/subdir/package.json"
-]
+]