fix: preserve trailing slashes in nested dep URLs (#42) (#43)

filepath.Join strips trailing slashes, so expandDepURL lost them for
nested dependencies. Re-append the slash after computing the relative
path when the original filePath ended with "/" or was empty.

Closes #42

Assisted-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bennypowers

resolve/local/local.go

@@ -907,7 +907,11 @@ func (r *Resolver) expandDepURL(depName, filePath string, nested bool, depPath,
 	if err != nil {
 		return r.template.Expand(depName, "", filePath)
 	}
-	return "/" + filepath.ToSlash(rel)
+	result := "/" + filepath.ToSlash(rel)
+	if strings.HasSuffix(filePath, "/") || filePath == "" {
+		result += "/"
+	}
+	return result
 }
 
 // parsePackageName extracts the package name from a package spec.

resolve/local/local_test.go

@@ -64,6 +64,8 @@ func TestResolver(t *testing.T) {
 		{"circular dependencies", "circular-deps"},
 		{"nested node_modules", "nested-node-modules"},
 		{"peer dependencies in scopes", "with-peer-deps"},
+		{"nested dep trailing-slash exports", "nested-trailing-slash"},
+		{"mixed nested and hoisted with wildcards", "nested-mixed-hoisted"},
 	}
 
 	for _, tt := range tests {

testdata/resolve/nested-mixed-hoisted/expected.json

@@ -0,0 +1,18 @@
+{
+  "imports": {
+    "alpha": "/node_modules/alpha/index.js",
+    "beta": "/node_modules/beta/index.js",
+    "shared-lib": "/node_modules/shared-lib/index.js",
+    "shared-lib/": "/node_modules/shared-lib/src/"
+  },
+  "scopes": {
+    "/node_modules/alpha/": {
+      "shared-lib": "/node_modules/alpha/node_modules/shared-lib/v1.js",
+      "shared-lib/": "/node_modules/alpha/node_modules/shared-lib/lib/"
+    },
+    "/node_modules/beta/": {
+      "shared-lib": "/node_modules/shared-lib/index.js",
+      "shared-lib/": "/node_modules/shared-lib/src/"
+    }
+  }
+}

testdata/resolve/nested-mixed-hoisted/node_modules/alpha/node_modules/shared-lib/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "mixed-test",
+  "dependencies": {
+    "alpha": "^1.0.0",
+    "beta": "^1.0.0",
+    "shared-lib": "^2.0.0"
+  }
+}

testdata/resolve/nested-mixed-hoisted/node_modules/alpha/package.json

@@ -0,0 +1,14 @@
+{
+  "imports": {
+    "parent-pkg": "/node_modules/parent-pkg/index.js"
+  },
+  "scopes": {
+    "/node_modules/parent-pkg/": {
+      "@nested/lib": "/node_modules/parent-pkg/node_modules/@nested/lib/index.js",
+      "@nested/lib/": "/node_modules/parent-pkg/node_modules/@nested/lib/src/",
+      "@nested/lib/controllers/": "/node_modules/parent-pkg/node_modules/@nested/lib/controllers/",
+      "no-exports-dep": "/node_modules/parent-pkg/node_modules/no-exports-dep/index.js",
+      "no-exports-dep/": "/node_modules/parent-pkg/node_modules/no-exports-dep/"
+    }
+  }
+}