addresses issue #252

ignore fields with no values

Signed-off-by: Tim Bray <[email protected]>

Author: timbray

PATTERNS.md

@@ -105,7 +105,7 @@ The following pattern will not match:
 
 We may be able to change this in future.
 
-The case of empty arrays is interesting. Consider this event:
+The case of empty arrays is interesting, both in Patterns and Events. Consider this event:
 
 ```json
 { "a": [] }
@@ -123,6 +123,16 @@ I.e., only the first of the two sample patterns below matches.
 This makes sense in the context of the leaf-node semantics; there
 really is no value for the `"a"` field.
 
+In Patterns, the following never matches any Event:
+
+```json
+{ "a": [] }
+```
+
+Once again, there is nothing in the array of candidate values in the Pattern that can match any value of an `"a"`
+field in an Event.
+
+
 
 ### Anything-But Pattern
 

core_matcher.go

@@ -80,6 +80,12 @@ func (m *coreMatcher) addPattern(x X, patternJSON string) error {
 	// combo.
 	states := []*fieldMatcher{currentFields.state}
 	for _, field := range patternFields {
+
+		// if the field has no values, this is a no-op
+		if len(field.vals) == 0 {
+			continue
+		}
+
 		var nextStates []*fieldMatcher
 
 		// separate handling for field exists:true/false and regular field name/val matches. Since the exists

pattern_test.go

@@ -41,6 +41,60 @@ func TestPatternErrorHandling(t *testing.T) {
 	}
 }
 
+// test that adding an empty pattern doesn't screw anything up
+func TestEmptyValueArray(t *testing.T) {
+	var err error
+	empties := []string{
+		`{"data": {"field": []}}`,
+		`{"data": {"field": [], "field2": [23]}}`,
+		`{"data": {"field2": [], "field": [23]}}`,
+	}
+	wanted := map[string][]X{
+		`{"data": {"field": 23}}`:  {empties[2]},
+		`{"data": {"field2": 23}}`: {empties[1]},
+		`{"data": {"field": []}}`:  {},
+	}
+	cm := newCoreMatcher()
+	defer func() {
+		if r := recover(); r != nil {
+			t.Errorf("addPattern panicked")
+		}
+	}()
+	for _, empty := range empties {
+		err = cm.addPattern(empty, empty)
+		if err != nil {
+			t.Error("addPattern: " + err.Error())
+		}
+	}
+
+	for want, _ := range wanted {
+		matches, err := cm.matchesForJSONEvent([]byte(want))
+		if err != nil {
+			t.Errorf("m4je err on %s", want)
+		}
+		checkXEqual(wanted[want], matches, t)
+	}
+}
+func checkXEqual(x1s []X, x2s []X, t *testing.T) {
+	x2size := len(x2s)
+	for _, x1 := range x1s {
+		count := 0
+		for _, x2 := range x2s {
+			if x1 == x2 {
+				count++
+			}
+		}
+		if count != 1 {
+			t.Errorf("for %s in X1, %d", x1, count)
+		} else {
+			x2size--
+		}
+	}
+	if x2size != 0 {
+		t.Error("Extra elements in X2")
+	}
+}
+
 func TestPatternFromJSON(t *testing.T) {
 	bads := []string{
 		`x`,