gps: handle symlinks properly

We now delete anything that looks like a symlink if its called
"vendor" while pruning.

Hopefully, you didn't make a bad decision by relying on the magical
properties of symlinks.

Signed-off-by: Ibrahim AshShohail <ibra.sho@gmail.com>

gps/filesystem.go

@@ -104,13 +104,9 @@ func deriveFilesystemState(root string) (filesystemState, error) {
 			l := fsLink{path: relPath}
 
 			l.to, err = filepath.EvalSymlinks(path)
-			if strings.HasSuffix(err.Error(), "too many links") {
+			if err != nil && strings.HasSuffix(err.Error(), "too many links") {
 				l.circular = true
-			} else if err != nil {
-				return err
-			}
-
-			if _, err := os.Stat(l.to); os.IsNotExist(err) {
+			} else if err != nil && os.IsNotExist(err) {
 				l.broken = true
 			} else if err != nil {
 				return err

gps/filesystem_test.go

@@ -5,6 +5,7 @@
 package gps
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"reflect"
@@ -99,28 +100,121 @@ func (tc fsTestCase) setup(t *testing.T) {
 
 func TestDeriveFilesystemState(t *testing.T) {
 	testcases := []struct {
-		name  string
-		state filesystemState
+		name string
+		fs   fsTestCase
 	}{
 		{
-			name:  "simple-case",
-			state: filesystemState{},
+			name: "simple-case",
+			fs: fsTestCase{
+				before: filesystemState{
+					dirs: []string{
+						"simple-dir",
+					},
+					files: []string{
+						"simple-file",
+					},
+				},
+				after: filesystemState{
+					dirs: []string{
+						"simple-dir",
+					},
+					files: []string{
+						"simple-file",
+					},
+				},
+			},
+		},
+		{
+			name: "simple-symlink-case",
+			fs: fsTestCase{
+				before: filesystemState{
+					dirs: []string{
+						"simple-dir",
+					},
+					files: []string{
+						"simple-file",
+					},
+					links: []fsLink{
+						fsLink{
+							path:   "link",
+							to:     "nonexisting",
+							broken: true,
+						},
+					},
+				},
+				after: filesystemState{
+					dirs: []string{
+						"simple-dir",
+					},
+					files: []string{
+						"simple-file",
+					},
+					links: []fsLink{
+						fsLink{
+							path:   "link",
+							to:     "",
+							broken: true,
+						},
+					},
+				},
+			},
+		},
+		{
+			name: "complex-symlink-case",
+			fs: fsTestCase{
+				before: filesystemState{
+					links: []fsLink{
+						fsLink{
+							path:     "link1",
+							to:       "link2",
+							circular: true,
+						},
+						fsLink{
+							path:     "link2",
+							to:       "link1",
+							circular: true,
+						},
+					},
+				},
+				after: filesystemState{
+					links: []fsLink{
+						fsLink{
+							path:     "link1",
+							to:       "",
+							circular: true,
+						},
+						fsLink{
+							path:     "link2",
+							to:       "",
+							circular: true,
+						},
+					},
+				},
+			},
 		},
 	}
 
 	for _, tc := range testcases {
 		h := test.NewHelper(t)
-		defer h.Cleanup()
 
 		h.TempDir(tc.name)
 
+		tc.fs.before.root = h.Path(tc.name)
+		tc.fs.after.root = h.Path(tc.name)
+
+		tc.fs.setup(t)
+
 		state, err := deriveFilesystemState(h.Path(tc.name))
 		if err != nil {
 			t.Fatal(err)
 		}
 
-		if !reflect.DeepEqual(tc.state, state) {
+		if !reflect.DeepEqual(tc.fs.after, state) {
+			fmt.Println(tc.fs.after)
+			fmt.Println(state)
 			t.Fatal("filesystem state mismatch")
 		}
+
+		h.Cleanup()
 	}
 }