add tag builder for slices

Signed-off-by: jkoberg <jkoberg@owncloud.com>

changelog/unreleased/fix-tags-pkg.md

@@ -0,0 +1,5 @@
+Enhancement: Fix tag pkg
+
+`tags` pkg needed an option to build the tags struct from a slice of tags. Here it is
+
+https://github.com/cs3org/reva/pull/3564

pkg/tags/tags.go

@@ -39,18 +39,23 @@ type Tags struct {
 	numtags int
 }
 
-// FromList creates a Tags struct from a list of tags
-func FromList(s string) *Tags {
-	t := &Tags{sep: _tagsep, maxtags: _maxtags, exists: make(map[string]bool)}
-	t.t = t.addTags(s)
+// FromSlice creates a Tag struct from a slice of tags, e.g. ["tag1", "tag2"]
+func FromSlice(ts []string) *Tags {
+	t := &Tags{sep: _tagsep, maxtags: _maxtags, exists: make(map[string]bool), t: make([]string, 0)}
+	for i := len(ts) - 1; i >= 0; i-- {
+		t.addTags(ts[i])
+	}
 	return t
 }
 
+// FromList creates a Tags struct from a list of tags, e.g. "tag1,tag2"
+func FromList(s string) *Tags {
+	return FromSlice([]string{s})
+}
+
 // AddList appends a list of new tags and returns true if at least one was appended
 func (t *Tags) AddList(s string) bool {
-	tags := t.addTags(s)
-	t.t = append(tags, t.t...)
-	return len(tags) > 0
+	return len(t.addTags(s)) > 0
 }
 
 // RemoveList removes a list of tags and returns true if at least one was removed
@@ -108,5 +113,6 @@ func (t *Tags) addTags(s string) []string {
 		t.numtags++
 	}
 
+	t.t = append(added, t.t...)
 	return added
 }

pkg/tags/tags_test.go

@@ -179,3 +179,29 @@ func TestRemoveTags(t *testing.T) {
 	}
 
 }
+
+func TestBuilders(t *testing.T) {
+	testCases := []struct {
+		Alias string
+		List  string
+		Slice []string
+	}{
+		{
+			Alias: "simple",
+			List:  "a,b,c",
+			Slice: []string{"a", "b", "c"},
+		},
+		{
+			Alias: "zero values",
+			List:  "",
+			Slice: nil,
+		},
+	}
+
+	for _, tc := range testCases {
+		list := FromList(tc.List)
+		slice := FromSlice(tc.Slice)
+
+		require.Equal(t, list, slice)
+	}
+}