Go plugin: keep float parameters typed (#33162)

plugin/go.go

@@ -202,11 +202,25 @@ func (p *Go) evaluate(vm *interp.Interpreter) (res any, err error) {
 
 func (p *Go) setParam(vm *interp.Interpreter) func(param string, val any) error {
 	return func(param string, val any) error {
-		_, err := vm.Eval(fmt.Sprintf("%s := %#v;", param, val))
+		_, err := vm.Eval(fmt.Sprintf("%s := %s;", param, goLiteral(val)))
 		return err
 	}
 }
 
+// goLiteral renders val as Go source. Floats need their type spelled out:
+// %#v prints float64(100) as `100`, which the interpreter infers as int. Any
+// arithmetic mixing the parameter with a float constant then fails to compile.
+func goLiteral(val any) string {
+	switch v := val.(type) {
+	case float32:
+		return fmt.Sprintf("float32(%v)", v)
+	case float64:
+		return fmt.Sprintf("float64(%v)", v)
+	default:
+		return fmt.Sprintf("%#v", val)
+	}
+}
+
 var _ IntSetter = (*Go)(nil)
 
 // IntSetter sends int request

plugin/go_test.go

@@ -0,0 +1,71 @@
+package plugin
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+// A float parameter must keep its type inside the interpreter even when the
+// value is a whole number. Otherwise arithmetic mixing it with a float constant
+// fails with "invalid operation: mismatched types int and untyped float".
+func TestGoFloatParam(t *testing.T) {
+	for _, tc := range []struct {
+		value float64
+		want  int64
+	}{
+		{11000, 73},
+		{15000, 100},
+		{0, 0},
+		{11000.5, 73},
+	} {
+		p, err := NewGoPluginFromConfig(t.Context(), map[string]any{
+			"in": []map[string]any{{
+				"name":   "limit",
+				"type":   "float",
+				"config": map[string]any{"source": "const", "value": tc.value},
+			}},
+			"script": "int(limit*100/15000 + 0.5)",
+		})
+		assert.NoError(t, err)
+
+		g, err := p.(IntGetter).IntGetter()
+		assert.NoError(t, err)
+
+		v, err := g()
+		assert.NoError(t, err)
+		assert.Equal(t, tc.want, v, tc.value)
+	}
+}
+
+// int parameters keep integer semantics
+func TestGoIntParam(t *testing.T) {
+	p, err := NewGoPluginFromConfig(t.Context(), map[string]any{
+		"in": []map[string]any{{
+			"name":   "mode",
+			"type":   "int",
+			"config": map[string]any{"source": "const", "value": 3},
+		}},
+		"script": "mode & 1",
+	})
+	assert.NoError(t, err)
+
+	g, err := p.(IntGetter).IntGetter()
+	assert.NoError(t, err)
+
+	v, err := g()
+	assert.NoError(t, err)
+	assert.Equal(t, int64(1), v)
+}
+
+// the value handed to a setter is a parameter, too
+func TestGoFloatSetter(t *testing.T) {
+	p, err := NewGoPluginFromConfig(t.Context(), map[string]any{
+		"script": "int(limit*100/15000 + 0.5)",
+	})
+	assert.NoError(t, err)
+
+	s, err := p.(FloatSetter).FloatSetter("limit")
+	assert.NoError(t, err)
+	assert.NoError(t, s(11000))
+}