Treat $XDG_DATA_DIRS as semicolon-delimited on Windows.

pkg/shell/paths.go

@@ -5,7 +5,6 @@ import (
 	"io"
 	"os"
 	"path/filepath"
-	"strings"
 
 	"src.elv.sh/pkg/daemon/daemondefs"
 	"src.elv.sh/pkg/env"
@@ -50,9 +49,10 @@ func libPaths(w io.Writer) ([]string, error) {
 	}
 
 	if dataDirs := os.Getenv(env.XDG_DATA_DIRS); dataDirs != "" {
-		// We intentionally do not use filepath.SplitList and always follow the
-		// semantics of XDG, even on Windows.
-		for _, dataDir := range strings.Split(dataDirs, ":") {
+		// XDG requires the paths be joined with ":". However, on Windows ":"
+		// appear after the drive letter, so it's infeasible to use it to also
+		// join paths.
+		for _, dataDir := range filepath.SplitList(dataDirs) {
 			paths = append(paths, filepath.Join(dataDir, "elvish", "lib"))
 		}
 	} else {

pkg/shell/shell_test.go

@@ -53,7 +53,8 @@ func TestShell_LibPath_XDGPaths(t *testing.T) {
 			},
 		},
 	}, xdgDataDir2)
-	testutil.Setenv(t, env.XDG_DATA_DIRS, xdgDataDir1+":"+xdgDataDir2)
+	testutil.Setenv(t, env.XDG_DATA_DIRS,
+		xdgDataDir1+string(filepath.ListSeparator)+xdgDataDir2)
 
 	Test(t, &Program{},
 		ThatElvish("-c", "use a").WritesStdout("a from xdg-config-home\n"),

website/ref/command.md

@@ -81,7 +81,8 @@ directories:
     `%LocalAppData%\elvish\lib` (Windows) is searched.
 
 3.  If the `XDG_DATA_DIRS` environment variable is defined and non-empty, it is
-    treated as a colon-delimited list of paths, which are all searched.
+    treated as a colon-delimited list of paths (semicolon-delimited on Windows),
+    which are all searched.
 
     Otherwise, `/usr/local/share/elvish/lib` and `/usr/share/elvish/lib` are
     searched on non-Windows OSes. On Windows, no directories are searched.