filter: lua: fieldName and fieldByName

Author: arl

filter/lua.go

@@ -87,10 +87,21 @@ func registerLUATypes(l *lua.LState, comp baker.ComponentParams) {
 		return 2
 	}))
 
-	// Create the fields table.
+	l.SetGlobal("fieldByName", l.NewFunction(func(L *lua.LState) int {
+		fname := L.CheckString(1)
+		fidx, ok := comp.FieldByName(fname)
+		if !ok {
+			l.Push(lua.LNil)
+		} else {
+			l.Push(lua.LNumber(fidx))
+		}
+		return 1
+	}))
+
+	// Create the fieldNaames table.
 	fields := l.NewTable()
-	for i, n := range comp.FieldNames {
-		fields.RawSetString(n, lua.LNumber(i))
+	for fidx, fname := range comp.FieldNames {
+		fields.RawSet(lua.LNumber(fidx), lua.LString(fname))
 	}
 	l.SetGlobal("fieldNames", fields)
 }

filter/lua_test.go

@@ -87,19 +87,26 @@ func TestLUAFilter(t *testing.T) {
 		want    [][3]string // contains non discarded records with, for each of them, the 3 fields we want
 	}{
 		{
-			name:   "swapFieldsWithIndex",
+			name:   "swapFields",
 			record: "abc,def,ghi",
 			want: [][3]string{
 				{"abc", "ghi", "def"},
 			},
 		},
 		{
-			name:   "swapFieldsWithNames",
+			name:   "_fieldByName",
 			record: "abc,def,ghi",
 			want: [][3]string{
 				{"abc", "ghi", "def"},
 			},
 		},
+		{
+			name:   "_fieldNames",
+			record: "abc,def,ghi",
+			want: [][3]string{
+				{"foo", "bar", "baz"},
+			},
+		},
 		{
 			name:   "_createRecord",
 			record: "abc,def,ghi",

filter/testdata/lua_test.lua

@@ -1,19 +1,27 @@
-function swapFieldsWithIndex(rec, next)
+function swapFields(rec, next)
     local f1, f2
     f1 = rec:get(1)
     rec:set(1, rec:get(2))
     rec:set(2, f1)
     next(rec)
 end
 
-function swapFieldsWithNames(rec, next)
+function _fieldByName(rec, next)
     local f1, f2
-    f1 = rec:get(fieldNames["bar"])
-    rec:set(1, rec:get(fieldNames["baz"]))
+    f1 = rec:get(fieldByName("bar"))
+    rec:set(1, rec:get(fieldByName("baz")))
     rec:set(2, f1)
     next(rec)
 end
 
+function _fieldNames(rec, next)
+    -- set each field to its name
+    rec:set(0, fieldNames[0])
+    rec:set(1, fieldNames[1])
+    rec:set(2, fieldNames[2])
+    next(rec)
+end
+
 function _createRecord(rec, next)
     newrec = createRecord()
     newrec:set(0, "hey")