memfs: add function to Merge one or more instance of MemFS

The Merge function merge one or more instance of MemFS into single MemFS
instance.

If there are two instance of Node that have the same path, the last
instance will be ignored.

1 files changed, 74 insertions, 0 deletions

diff --git a/lib/memfs/memfs_test.go b/lib/memfs/memfs_test.go
index fc680401..8a130e42 100644
--- a/lib/memfs/memfs_test.go
+++ b/lib/memfs/memfs_test.go
@@ -478,3 +478,77 @@ func TestMain(m *testing.M) {
 
 	os.Exit(m.Run())
 }
+
+func TestMerge(t *testing.T) {
+	optsDirect := &Options{
+		Root: "testdata/direct",
+	}
+	mfsDirect, err := New(optsDirect)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	optsInclude := &Options{
+		Root: "testdata/include",
+	}
+	mfsInclude, err := New(optsInclude)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	cases := []struct {
+		desc   string
+		params []*MemFS
+		exp    *MemFS
+	}{{
+		desc:   "with the same instance",
+		params: []*MemFS{mfsDirect, mfsDirect},
+		exp: &MemFS{
+			PathNodes: &PathNode{
+				v: map[string]*Node{
+					"/": &Node{
+						SysPath: "..",
+						Path:    "/",
+						Childs: []*Node{
+							mfsDirect.MustGet("/add"),
+						},
+					},
+					"/add":       mfsDirect.MustGet("/add"),
+					"/add/file":  mfsDirect.MustGet("/add/file"),
+					"/add/file2": mfsDirect.MustGet("/add/file2"),
+				},
+			},
+		},
+	}, {
+		desc:   "with different instances",
+		params: []*MemFS{mfsDirect, mfsInclude},
+		exp: &MemFS{
+			PathNodes: &PathNode{
+				v: map[string]*Node{
+					"/": &Node{
+						SysPath: "..",
+						Path:    "/",
+						Childs: []*Node{
+							mfsDirect.MustGet("/add"),
+							mfsInclude.MustGet("/index.css"),
+							mfsInclude.MustGet("/index.html"),
+							mfsInclude.MustGet("/index.js"),
+						},
+					},
+					"/add":        mfsDirect.MustGet("/add"),
+					"/add/file":   mfsDirect.MustGet("/add/file"),
+					"/add/file2":  mfsDirect.MustGet("/add/file2"),
+					"/index.css":  mfsInclude.MustGet("/index.css"),
+					"/index.html": mfsInclude.MustGet("/index.html"),
+					"/index.js":   mfsInclude.MustGet("/index.js"),
+				},
+			},
+		},
+	}}
+
+	for _, c := range cases {
+		got := Merge(c.params...)
+
+		test.Assert(t, c.desc, c.exp.PathNodes.v, got.PathNodes.v)
+	}
+}