ui.FileSelector logic and tests

internal/app/ui/filesystem.go

@@ -10,12 +10,19 @@ import (
 )
 
 type fileSelectorOpt struct {
-	emptyFilename string // if set, the empty filename will be replaced to this value
+	defaultFilename string // if set, the empty filename will be replaced to this value
+	mustExist       bool
 }
 
-func WithEmptyFilename(s string) Option {
-	return func(so *inputOptions) {
-		so.fileSelectorOpt.emptyFilename = s
+func WithDefaultFilename(s string) Option {
+	return func(io *inputOptions) {
+		io.fileSelectorOpt.defaultFilename = s
+	}
+}
+
+func WithMustExist(b bool) Option {
+	return func(io *inputOptions) {
+		io.mustExist = b
 	}
 }
 
@@ -34,10 +41,22 @@ func FileSelector(msg, descr string, opt ...Option) (string, error) {
 				Help: descr,
 			},
 			Validate: func(ans interface{}) error {
-				if ans.(string) != "" || opts.emptyFilename != "" {
-					return nil
+				filename := ans.(string)
+				if filename == "" {
+					if opts.defaultFilename == "" {
+						return errors.New("empty filename")
+					} else {
+						if !opts.mustExist {
+							return nil
+						} else {
+							return checkExists(opts.defaultFilename)
+						}
+					}
 				}
-				return errors.New("empty filename")
+				if opts.mustExist {
+					return checkExists(filename)
+				}
+				return nil
 			},
 		},
 	}
@@ -49,8 +68,11 @@ func FileSelector(msg, descr string, opt ...Option) (string, error) {
 		if err := survey.Ask(q, &resp, opts.surveyOpts()...); err != nil {
 			return "", err
 		}
-		if resp.Filename == "" && opts.emptyFilename != "" {
-			resp.Filename = opts.emptyFilename
+		if resp.Filename == "" && opts.defaultFilename != "" {
+			resp.Filename = opts.defaultFilename
+		}
+		if opts.mustExist {
+			break
 		}
 		if _, err := os.Stat(resp.Filename); err != nil {
 			break
@@ -65,3 +87,14 @@ func FileSelector(msg, descr string, opt ...Option) (string, error) {
 	}
 	return resp.Filename, nil
 }
+
+func checkExists(filename string) error {
+	if _, err := os.Stat(filename); err != nil {
+		if os.IsNotExist(err) {
+			return errors.New("file must exist")
+		} else {
+			return err
+		}
+	}
+	return nil
+}

internal/app/ui/filesystem_test.go

@@ -17,7 +17,7 @@ func init() {
 }
 
 func TestFileselector(t *testing.T) {
-	t.Run("default", func(t *testing.T) {
+	t.Run("filename set", func(t *testing.T) {
 		var filename string
 		testFn := func(stdio terminal.Stdio) error {
 			var err error
@@ -32,7 +32,7 @@ func TestFileselector(t *testing.T) {
 		RunTest(t, procedure, testFn)
 		assert.Equal(t, "test.txt", filename)
 	})
-	t.Run("empty with no override", func(t *testing.T) {
+	t.Run("empty, default not set", func(t *testing.T) {
 		var filename string
 		testFn := func(stdio terminal.Stdio) error {
 			var err error
@@ -50,11 +50,11 @@ func TestFileselector(t *testing.T) {
 		RunTest(t, procedure, testFn)
 		assert.Equal(t, ":wq!", filename)
 	})
-	t.Run("empty with the override", func(t *testing.T) {
+	t.Run("empty, default set", func(t *testing.T) {
 		var filename string
 		testFn := func(stdio terminal.Stdio) error {
 			var err error
-			filename, err = FileSelector("xxx", "help", WithOutput(stdio), WithEmptyFilename("override"))
+			filename, err = FileSelector("xxx", "help", WithOutput(stdio), WithDefaultFilename("default_filename"))
 			return err
 		}
 		procedure := func(t *testing.T, c console) {
@@ -63,9 +63,9 @@ func TestFileselector(t *testing.T) {
 			c.ExpectEOF()
 		}
 		RunTest(t, procedure, testFn)
-		assert.Equal(t, "override", filename)
+		assert.Equal(t, "default_filename", filename)
 	})
-	t.Run("overwrite", func(t *testing.T) {
+	t.Run("filename set and exist", func(t *testing.T) {
 		var filename string
 		dir := t.TempDir()
 		testfile := filepath.Join(dir, "testfile.txt")
@@ -88,4 +88,52 @@ func TestFileselector(t *testing.T) {
 			})
 		assert.Equal(t, testfile, filename)
 	})
+	t.Run("filename set, default empty, must exist set", func(t *testing.T) {
+		var filename string
+		dir := t.TempDir()
+		testfile := filepath.Join(dir, "testfile.txt")
+		if err := os.WriteFile(testfile, []byte("unittest"), 0666); err != nil {
+			t.Fatal(err)
+		}
+		RunTest(
+			t,
+			func(t *testing.T, c console) {
+				// attempt 1.
+				c.ExpectString("non-existing")
+				c.SendLine(filepath.Join(dir, "$$$$.XXX"))
+				c.ExpectString("file must exist")
+				// attempt 2.
+				c.ExpectString("non-existing")
+				c.SendLine(testfile)
+				c.ExpectEOF()
+			},
+			func(s terminal.Stdio) error {
+				var err error
+				filename, err = FileSelector("non-existing test", "", WithOutput(s), WithMustExist(true))
+				return err
+			})
+		assert.Equal(t, testfile, filename)
+	})
+	t.Run("filename not set, default set, must exist set", func(t *testing.T) {
+		var filename string
+		dir := t.TempDir()
+		testfile := filepath.Join(dir, "testfile.txt")
+		if err := os.WriteFile(testfile, []byte("unittest"), 0666); err != nil {
+			t.Fatal(err)
+		}
+		RunTest(
+			t,
+			func(t *testing.T, c console) {
+				// attempt 1.
+				c.ExpectString("variant 4")
+				c.SendLine("")
+				c.ExpectEOF()
+			},
+			func(s terminal.Stdio) error {
+				var err error
+				filename, err = FileSelector("variant 4", "", WithOutput(s), WithDefaultFilename(testfile), WithMustExist(true))
+				return err
+			})
+		assert.Equal(t, testfile, filename)
+	})
 }