Prefix matching splat

Fixes https://github.com/mikefarah/yq/issues/218

data_navigator.go

@@ -4,15 +4,25 @@ import (
 	"fmt"
 	"reflect"
 	"strconv"
+	"strings"
 
 	yaml "gopkg.in/mikefarah/yaml.v2"
 )
 
-func entriesInSlice(context yaml.MapSlice, key interface{}) []*yaml.MapItem {
+func matchesKey(key string, actual interface{}) bool {
+	var actualString = fmt.Sprintf("%v", actual)
+	var prefixMatch = strings.TrimSuffix(key, "*")
+	if prefixMatch != key {
+		return strings.HasPrefix(actualString, prefixMatch)
+	}
+	return actualString == key
+}
+
+func entriesInSlice(context yaml.MapSlice, key string) []*yaml.MapItem {
 	var matches = make([]*yaml.MapItem, 0)
 	for idx := range context {
 		var entry = &context[idx]
-		if key == "*" || fmt.Sprintf("%v", entry.Key) == key {
+		if matchesKey(key, entry.Key) {
 			matches = append(matches, entry)
 		}
 	}

data_navigator_test.go

@@ -31,12 +31,22 @@ func TestReadMap_splat(t *testing.T) {
 mapSplat:
   item1: things
   item2: whatever
+  otherThing: cat
 `)
 	res, _ := readMap(data, "mapSplat", []string{"*"})
-	result := res.([]interface{})
+	assertResult(t, "[things whatever cat]", fmt.Sprintf("%v", res))
-	var actual = []string{result[0].(string), result[1].(string)}
+}
-	sort.Strings(actual)
+
-	assertResult(t, "[things whatever]", fmt.Sprintf("%v", actual))
+func TestReadMap_prefixSplat(t *testing.T) {
+	var data = parseData(`
+---
+mapSplat:
+  item1: things
+  item2: whatever
+  otherThing: cat
+`)
+	res, _ := readMap(data, "mapSplat", []string{"item*"})
+	assertResult(t, "[things whatever]", fmt.Sprintf("%v", res))
 }
 
 func TestReadMap_deep_splat(t *testing.T) {

examples/data3.yaml

@@ -1 +1,14 @@
-b: dog
+deep1:
+   hostA:
+      value: 1234
+   notRelevant:
+      value: bananas
+   hostB:
+      value: 5678
+deep2:
+   hostC:
+      value: 1234
+   notRelevant:
+      value: bananas
+   hostD:
+      value: 5678