Adjust print formatting (deepnoodle-ai#250)

Author: myzie

cmd/risor-modgen/main.go

@@ -283,7 +283,7 @@ func {{ .FuncGenName }}(ctx context.Context, args ...object.Object) object.Objec
 // Useful if you want to write your own "Module()" function.
 func addGeneratedBuiltins(builtins map[string]object.Object) map[string]object.Object {
 	{{- range .ExportedFuncs }}
-	builtins["{{ .ExportedName }}"] = object.NewBuiltin("{{ $.Package }}.{{ .ExportedName }}", {{ .FuncGenName }})
+	builtins["{{ .ExportedName }}"] = object.NewBuiltin("{{ .ExportedName }}", {{ .FuncGenName }})
 	{{- end }}
 	return builtins
 }

modules/fmt/fmt.go

@@ -4,16 +4,36 @@ import (
 	"context"
 	_ "embed"
 	"fmt"
+	"time"
 
 	"github.com/risor-io/risor/object"
 	"github.com/risor-io/risor/os"
 )
 
 func printableValue(obj object.Object) interface{} {
-	iface := obj.Interface()
-	if iface != nil {
-		return iface
+	switch obj := obj.(type) {
+	// Primitive types have their underlying Go value passed to fmt.Printf
+	// so that Go's Printf-style formatting directives work as expected. Also,
+	// with these types there's no good reason for the print format to differ.
+	case *object.String,
+		*object.Int,
+		*object.Float,
+		*object.Byte,
+		*object.Error,
+		*object.Bool,
+		*object.NilType:
+		return obj.Interface()
+	// For time objects, as a personal preference, I'm using RFC3339 format
+	// rather than Go's default time print format, which I find less readable.
+	case *object.Time:
+		return obj.Value().Format(time.RFC3339)
 	}
+	// For everything else, convert the object to a string directly, relying
+	// on the object type's String() or Inspect() methods. This gives the author
+	// of new types the ability to customize the object print string. Note that
+	// Risor map and list objects fall into this category on purpose and the
+	// print format for these is intentionally a bit different than the print
+	// format for the equivalent Go type (maps and slices).
 	switch obj := obj.(type) {
 	case fmt.Stringer:
 		return obj.String()

modules/fmt/fmt_test.go

@@ -0,0 +1,67 @@
+package fmt
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+	"time"
+
+	"github.com/risor-io/risor/object"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPrintableValue(t *testing.T) {
+	type testCase struct {
+		obj      object.Object
+		expected any
+	}
+
+	testTime, err := time.Parse("2006-01-02", "2021-01-01")
+	require.NoError(t, err)
+
+	builtin := func(ctx context.Context, args ...object.Object) object.Object {
+		return nil
+	}
+
+	cases := []testCase{
+		{object.NewString("hello"), "hello"},
+		{object.NewByte(5), byte(5)},
+		{object.NewInt(42), int64(42)},
+		{object.NewFloat(42.42), 42.42},
+		{object.NewBool(true), true},
+		{object.NewBool(false), false},
+		{object.Errorf("error"), errors.New("error")},
+		{obj: object.Nil, expected: nil},
+		{obj: object.NewTime(testTime), expected: "2021-01-01T00:00:00Z"},
+		{obj: object.NewBuiltin("foo", builtin), expected: "builtin(foo)"},
+		{ // strings printed inside lists are quoted in Risor
+			obj: object.NewList([]object.Object{
+				object.NewString("hello"),
+				object.NewInt(42),
+			}),
+			expected: `["hello", 42]`,
+		},
+		{ // strings printed inside maps are quoted in Risor
+			obj: object.NewMap(map[string]object.Object{
+				"a": object.NewInt(42),
+				"b": object.NewString("hello"),
+				"c": object.Nil,
+			}),
+			expected: `{"a": 42, "b": "hello", "c": nil}`,
+		},
+		{
+			obj: object.NewSet([]object.Object{
+				object.NewInt(42),
+				object.NewString("hi there"),
+			}),
+			expected: `{42, "hi there"}`,
+		},
+	}
+	for _, tc := range cases {
+		t.Run(fmt.Sprintf("%v", tc.expected), func(t *testing.T) {
+			got := printableValue(tc.obj)
+			require.Equal(t, tc.expected, got)
+		})
+	}
+}