search: add attribute substring search

Change-Id: I3b30541c43b5fba84491b98ed73d34a64465c24e

pkg/search/predicate.go

@@ -233,7 +233,8 @@ func newAttribute() keyword {
 
 func (a attribute) Description() string {
 	return "match on attribute. Use attr:foo:bar to match nodes having their foo\n" +
-		"attribute set to bar."
+		"attribute set to bar or attr:foo:~bar to do a substring\n" +
+		"case-insensitive search for 'bar' in attribute foo"
 }
 
 func (a attribute) Predicate(ctx *context.Context, args []string) (*Constraint, error) {
@@ -244,6 +245,14 @@ func (a attribute) Predicate(ctx *context.Context, args []string) (*Constraint,
 			Value:      args[1],
 		},
 	}
+	if strings.HasPrefix(args[1], "~") {
+		// Substring. Hack. Figure out better way to do this.
+		c.Permanode.Value = ""
+		c.Permanode.ValueMatches = &StringConstraint{
+			Contains:        args[1][1:],
+			CaseInsensitive: true,
+		}
+	}
 	return c, nil
 }
 
@@ -539,8 +548,8 @@ func newHasLocation() keyword {
 }
 
 func (h hasLocation) Description() string {
-	return "matches images and permanodes that have a location (GPSLatitude and GPSLongitude can be\n" +
-		"retrieved from the image's EXIF tags)."
+	return "matches images and permanodes that have a location (GPSLatitude\n" +
+		"and GPSLongitude can be retrieved from the image's EXIF tags)."
 }
 
 func (h hasLocation) Predicate(ctx *context.Context, args []string) (*Constraint, error) {

pkg/search/predicate_test.go

@@ -190,6 +190,21 @@ var keywordTests = []keywordTestcase{
 		want:   attrfoobarC,
 	},
 
+	{
+		object: newAttribute(),
+		args:   []string{"foo", "~bar"},
+		want: &Constraint{
+			Permanode: &PermanodeConstraint{
+				Attr: "foo",
+				ValueMatches: &StringConstraint{
+					Contains:        "bar",
+					CaseInsensitive: true,
+				},
+				SkipHidden: true,
+			},
+		},
+	},
+
 	{
 		object: newChildrenOf(),
 		args:   []string{"foo"},