js: Fix import order for ./foo when both ./foo.js and ./foo/index.js exists

This is in line with how both Node and ESBuild's native import resolver does it.

The ambiguous situations above were discovered trying to build AlpineJS v3.

Note that the above was never an issue if you used `./foo.js` and similar to import the component.

Fixes #8945

resources/resource_transformers/js/options_test.go

@@ -14,8 +14,13 @@
 package js
 
 import (
+	"path/filepath"
 	"testing"
 
+	"github.com/gohugoio/hugo/hugofs"
+
+	"github.com/spf13/afero"
+
 	"github.com/gohugoio/hugo/media"
 
 	"github.com/evanw/esbuild/pkg/api"
@@ -127,3 +132,48 @@ func TestToBuildOptions(t *testing.T) {
 		},
 	})
 }
+
+func TestResolveComponentInAssets(t *testing.T) {
+	c := qt.New(t)
+
+	for _, test := range []struct {
+		name    string
+		files   []string
+		impPath string
+		expect  string
+	}{
+		{"Basic, extension", []string{"foo.js", "bar.js"}, "foo.js", "foo.js"},
+		{"Basic, no extension", []string{"foo.js", "bar.js"}, "foo", "foo.js"},
+		{"Basic, no extension, typescript", []string{"foo.ts", "bar.js"}, "foo", "foo.ts"},
+		{"Not found", []string{"foo.js", "bar.js"}, "moo.js", ""},
+		{"Not found, double js extension", []string{"foo.js.js", "bar.js"}, "foo.js", ""},
+		{"Index file, folder only", []string{"foo/index.js", "bar.js"}, "foo", "foo/index.js"},
+		{"Index file, folder and index", []string{"foo/index.js", "bar.js"}, "foo/index", "foo/index.js"},
+		{"Index file, folder and index and suffix", []string{"foo/index.js", "bar.js"}, "foo/index.js", "foo/index.js"},
+
+		// Issue #8949
+		{"Check file before directory", []string{"foo.js", "foo/index.js"}, "foo", "foo.js"},
+	} {
+
+		c.Run(test.name, func(c *qt.C) {
+			baseDir := "assets"
+			mfs := afero.NewMemMapFs()
+
+			for _, filename := range test.files {
+				c.Assert(afero.WriteFile(mfs, filepath.Join(baseDir, filename), []byte("let foo='bar';"), 0777), qt.IsNil)
+			}
+
+			bfs := hugofs.DecorateBasePathFs(afero.NewBasePathFs(mfs, baseDir).(*afero.BasePathFs))
+
+			got := resolveComponentInAssets(bfs, test.impPath)
+
+			gotPath := ""
+			if got != nil {
+				gotPath = filepath.ToSlash(got.Path)
+			}
+
+			c.Assert(gotPath, qt.Equals, test.expect)
+		})
+
+	}
+}