Make sure get() returns nil for map[string]string on missing keys

antonmedv · antonmedv · commit 435b79df38cd · 2025-03-08T17:28:39.000+01:00
Fixes #723
diff --git a/builtin/builtin.go b/builtin/builtin.go
@@ -627,14 +627,7 @@ var Builtins = []*Function{
 	},
 	{
 		Name: "get",
-		Func: func(args ...any) (out any, err error) {
-			defer func() {
-				if r := recover(); r != nil {
-					return
-				}
-			}()
-			return runtime.Fetch(args[0], args[1]), nil
-		},
+		Func: get,
 	},
 	{
 		Name: "take",
diff --git a/builtin/lib.go b/builtin/lib.go
@@ -8,6 +8,7 @@ import (
 	"unicode/utf8"
 
 	"github.com/expr-lang/expr/internal/deref"
+	"github.com/expr-lang/expr/vm/runtime"
 )
 
 func Len(x any) any {
@@ -367,3 +368,69 @@ func flatten(arg reflect.Value) []any {
 	}
 	return ret
 }
+
+func get(params ...any) (out any, err error) {
+	from := params[0]
+	i := params[1]
+	v := reflect.ValueOf(from)
+
+	if v.Kind() == reflect.Invalid {
+		panic(fmt.Sprintf("cannot fetch %v from %T", i, from))
+	}
+
+	// Methods can be defined on any type.
+	if v.NumMethod() > 0 {
+		if methodName, ok := i.(string); ok {
+			method := v.MethodByName(methodName)
+			if method.IsValid() {
+				return method.Interface(), nil
+			}
+		}
+	}
+
+	v = deref.Value(v)
+	i = deref.Deref(i)
+
+	switch v.Kind() {
+	case reflect.Array, reflect.Slice, reflect.String:
+		index := runtime.ToInt(i)
+		l := v.Len()
+		if index < 0 {
+			index = l + index
+		}
+		if 0 <= index && index < l {
+			value := v.Index(index)
+			if value.IsValid() {
+				return value.Interface(), nil
+			}
+		}
+
+	case reflect.Map:
+		var value reflect.Value
+		if i == nil {
+			value = v.MapIndex(reflect.Zero(v.Type().Key()))
+		} else {
+			value = v.MapIndex(reflect.ValueOf(i))
+		}
+		if value.IsValid() {
+			return value.Interface(), nil
+		}
+
+	case reflect.Struct:
+		fieldName := i.(string)
+		value := v.FieldByNameFunc(func(name string) bool {
+			field, _ := v.Type().FieldByName(name)
+			if field.Tag.Get("expr") == fieldName {
+				return true
+			}
+			return name == fieldName
+		})
+		if value.IsValid() {
+			return value.Interface(), nil
+		}
+	}
+
+	// Main difference from runtime.Fetch
+	// is that we return `nil` instead of panic.
+	return nil, nil
+}
diff --git a/test/fuzz/fuzz_corpus.txt b/test/fuzz/fuzz_corpus.txt
@@ -7088,58 +7088,33 @@ get(false ? i32 : list, i64)
 get(false ? i64 : true, f64)
 get(false ? score : ok, trimSuffix("bar", "bar"))
 get(filter(list, true), i)
-get(groupBy(array, "bar"), add)
 get(groupBy(array, "bar"), i)
 get(groupBy(array, "bar"), ok)
-get(groupBy(array, "foo"), half)
-get(groupBy(array, #), add)
-get(groupBy(array, #), array)
 get(groupBy(array, #), f32)
 get(groupBy(array, #), f64)
 get(groupBy(array, #), foo)
-get(groupBy(array, #), greet)
-get(groupBy(array, #), half)
 get(groupBy(array, #), i)
 get(groupBy(array, #), i64 * 0.5)
 get(groupBy(array, #), i64)
-get(groupBy(array, #)?.String, i64)
-get(groupBy(array, 0.5), add)
-get(groupBy(array, 0.5), div)
 get(groupBy(array, 0.5), ok)
-get(groupBy(array, 1), add)
 get(groupBy(array, 1), f32)
 get(groupBy(array, f64), i64)
 get(groupBy(array, false), findIndex(array, ok))
 get(groupBy(array, i), ok)
-get(groupBy(array, i), score)
-get(groupBy(array, i64), add)
-get(groupBy(array, ok), add)
 get(groupBy(array, true), i32)
 get(groupBy(list, "bar"), i32)
-get(groupBy(list, "foo"), greet)
-get(groupBy(list, #), div)
 get(groupBy(list, #), f32 <= f64)
 get(groupBy(list, #), f32)
 get(groupBy(list, #), foo)
-get(groupBy(list, #), greet)
-get(groupBy(list, #), half)
 get(groupBy(list, #), i)
 get(groupBy(list, #), i32)
 get(groupBy(list, #), i64)
 get(groupBy(list, #), int(f32))
-get(groupBy(list, #), list)
 get(groupBy(list, #), reduce(array, foo))
 get(groupBy(list, #), score(1))
-get(groupBy(list, #), score)
-get(groupBy(list, 0.5), array)
-get(groupBy(list, 0.5), div)
 get(groupBy(list, 0.5), ok)
 get(groupBy(list, 1), i32)
-get(groupBy(list, f32), greet)
-get(groupBy(list, foo), add)
 get(groupBy(list, foo), i32)
-get(groupBy(list, ok), greet)
-get(groupBy(list, ok), list)
 get(i .. 1, 1 * 1)
 get(i .. i32, i)
 get(i32 .. i, i64)
@@ -7200,12 +7175,10 @@ get(list, max(i32))
 get(list, min(i32))
 get(list, min(i64))
 get(list, ok ? 0.5 : "foo")
-get(list, ok ? array : "foo")
 get(list, reduce(list, i64))
 get(list, score(1))
 get(list, score(i))
 get(list, true ? i : i32)
-get(list, {"foo": i32}?.i)
 get(list[i64:1], i)
 get(map(array, #), i)
 get(map(array, #), i32)
@@ -7221,18 +7194,15 @@ get(map(list, 1), i32)
 get(map(list, array), i)
 get(map(list, i32), i64)
 get(map(list, i64), i64)
-get(ok ? "bar" : false, array)
 get(ok ? 1 : "bar", f32)
 get(ok ? add : f32, array)
 get(ok ? f64 : div, i64)
 get(ok ? false : list, f32 > i)
-get(ok ? foo : 0.5, div)
 get(ok ? half : i32, i)
 get(ok ? half : ok, f64)
 get(ok ? i : 0.5, half)
 get(ok ? i32 : half, f64)
 get(ok ? i64 : foo, f32)
-get(ok ? list : "foo", add)
 get(ok ? list : i32, f32)
 get(ok ? ok : div, greet)
 get(ok ? score : f64, i)
@@ -7241,7 +7211,6 @@ get(reduce(list, array), i32)
 get(sort(array), i32)
 get(take(list, i), i64)
 get(true ? "bar" : ok, score(i))
-get(true ? "foo" : half, list)
 get(true ? 0.5 : i32, array)
 get(true ? f32 : 0.5, ok)
 get(true ? false : foo, i64 > 0.5)
diff --git a/test/issues/723/issue_test.go b/test/issues/723/issue_test.go
@@ -0,0 +1,24 @@
+package issue_test
+
+import (
+	"testing"
+
+	"github.com/expr-lang/expr"
+	"github.com/expr-lang/expr/internal/testify/require"
+)
+
+func TestIssue723(t *testing.T) {
+	emptyMap := make(map[string]string)
+	env := map[string]interface{}{
+		"empty_map": emptyMap,
+	}
+
+	code := `get(empty_map, "non_existing_key")`
+
+	program, err := expr.Compile(code, expr.Env(env))
+	require.NoError(t, err)
+
+	output, err := expr.Run(program, env)
+	require.NoError(t, err)
+	require.Equal(t, nil, output)
+}
diff --git a/testdata/examples.txt b/testdata/examples.txt
@@ -7088,58 +7088,33 @@ get(false ? i32 : list, i64)
 get(false ? i64 : true, f64)
 get(false ? score : ok, trimSuffix("bar", "bar"))
 get(filter(list, true), i)
-get(groupBy(array, "bar"), add)
 get(groupBy(array, "bar"), i)
 get(groupBy(array, "bar"), ok)
-get(groupBy(array, "foo"), half)
-get(groupBy(array, #), add)
-get(groupBy(array, #), array)
 get(groupBy(array, #), f32)
 get(groupBy(array, #), f64)
 get(groupBy(array, #), foo)
-get(groupBy(array, #), greet)
-get(groupBy(array, #), half)
 get(groupBy(array, #), i)
 get(groupBy(array, #), i64 * 0.5)
 get(groupBy(array, #), i64)
-get(groupBy(array, #)?.String, i64)
-get(groupBy(array, 0.5), add)
-get(groupBy(array, 0.5), div)
 get(groupBy(array, 0.5), ok)
-get(groupBy(array, 1), add)
 get(groupBy(array, 1), f32)
 get(groupBy(array, f64), i64)
 get(groupBy(array, false), findIndex(array, ok))
 get(groupBy(array, i), ok)
-get(groupBy(array, i), score)
-get(groupBy(array, i64), add)
-get(groupBy(array, ok), add)
 get(groupBy(array, true), i32)
 get(groupBy(list, "bar"), i32)
-get(groupBy(list, "foo"), greet)
-get(groupBy(list, #), div)
 get(groupBy(list, #), f32 <= f64)
 get(groupBy(list, #), f32)
 get(groupBy(list, #), foo)
-get(groupBy(list, #), greet)
-get(groupBy(list, #), half)
 get(groupBy(list, #), i)
 get(groupBy(list, #), i32)
 get(groupBy(list, #), i64)
 get(groupBy(list, #), int(f32))
-get(groupBy(list, #), list)
 get(groupBy(list, #), reduce(array, foo))
 get(groupBy(list, #), score(1))
-get(groupBy(list, #), score)
-get(groupBy(list, 0.5), array)
-get(groupBy(list, 0.5), div)
 get(groupBy(list, 0.5), ok)
 get(groupBy(list, 1), i32)
-get(groupBy(list, f32), greet)
-get(groupBy(list, foo), add)
 get(groupBy(list, foo), i32)
-get(groupBy(list, ok), greet)
-get(groupBy(list, ok), list)
 get(i .. 1, 1 * 1)
 get(i .. i32, i)
 get(i32 .. i, i64)
@@ -7200,12 +7175,10 @@ get(list, max(i32))
 get(list, min(i32))
 get(list, min(i64))
 get(list, ok ? 0.5 : "foo")
-get(list, ok ? array : "foo")
 get(list, reduce(list, i64))
 get(list, score(1))
 get(list, score(i))
 get(list, true ? i : i32)
-get(list, {"foo": i32}?.i)
 get(list[i64:1], i)
 get(map(array, #), i)
 get(map(array, #), i32)
@@ -7221,18 +7194,15 @@ get(map(list, 1), i32)
 get(map(list, array), i)
 get(map(list, i32), i64)
 get(map(list, i64), i64)
-get(ok ? "bar" : false, array)
 get(ok ? 1 : "bar", f32)
 get(ok ? add : f32, array)
 get(ok ? f64 : div, i64)
 get(ok ? false : list, f32 > i)
-get(ok ? foo : 0.5, div)
 get(ok ? half : i32, i)
 get(ok ? half : ok, f64)
 get(ok ? i : 0.5, half)
 get(ok ? i32 : half, f64)
 get(ok ? i64 : foo, f32)
-get(ok ? list : "foo", add)
 get(ok ? list : i32, f32)
 get(ok ? ok : div, greet)
 get(ok ? score : f64, i)
@@ -7241,7 +7211,6 @@ get(reduce(list, array), i32)
 get(sort(array), i32)
 get(take(list, i), i64)
 get(true ? "bar" : ok, score(i))
-get(true ? "foo" : half, list)
 get(true ? 0.5 : i32, array)
 get(true ? f32 : 0.5, ok)
 get(true ? false : foo, i64 > 0.5)
