potential fix for #24

cmd/lgo-internal/kernel.go

@@ -162,8 +162,17 @@ func (h *handlers) HandleExecuteRequest(ctx context.Context, r *scaffold.Execute
 				fmt.Fprintf(os.Stderr, "panic: %v\n\n%s", p, debug.Stack())
 			}
 		}()
+
+		var f func(core.LgoContext, string) error
+		trimmedCode := strings.TrimSpace(r.Code)
+		if strings.Index(trimmedCode, "\n") == -1 && strings.HasPrefix(trimmedCode, "%"){
+			f = h.runner.RunMagics
+		} else  {
+			f = h.runner.Run
+		}
+
 		// Print the err in the notebook
-		if err = h.runner.Run(lgoCtx, r.Code); err != nil {
+		if err = f(lgoCtx, r.Code); err != nil {
 			runner.PrintError(os.Stderr, err)
 		}
 	}()

cmd/lgo-internal/magics/line_magics.go

@@ -0,0 +1,37 @@
+package magics
+
+import (
+	"time"
+	"github.com/yunabe/lgo/core"
+	"io/ioutil"
+	"fmt"
+	"strings"
+)
+
+var magics = map[string]func(ctx core.LgoContext, source string, runner func(core.LgoContext, string) error) error{
+	"run": run,
+	"time": timeMagic,
+}
+
+func run(ctx core.LgoContext, source string, runner func(core.LgoContext, string) error) error {
+	srcBytes, err := ioutil.ReadFile(strings.TrimSpace(source))
+	if err != nil {
+		core.LgoPrintln(fmt.Sprintf("Error while reading the file %s: %v", source, err))
+		return  err
+	}
+
+	runner(ctx, string(srcBytes))
+
+	return  nil
+}
+
+func timeMagic(ctx core.LgoContext, source string, runner func(core.LgoContext, string) error) error {
+	start := time.Now()
+	runner(ctx, source)
+	core.LgoPrintln(fmt.Sprintf("time taken: %v", time.Since(start)))
+	return  nil
+}
+
+func GetRegisteredMagics() map[string]func(ctx core.LgoContext, source string, runner func(core.LgoContext, string) error) error {
+	return  magics
+}

cmd/runner/runner.go

@@ -19,6 +19,7 @@ import (
 	"github.com/yunabe/lgo/cmd/install"
 	"github.com/yunabe/lgo/converter"
 	"github.com/yunabe/lgo/core"
+	"github.com/yunabe/lgo/cmd/lgo-internal/magics"
 )
 
 /*
@@ -259,3 +260,24 @@ func (rn *LgoRunner) Inspect(ctx context.Context, src string, index int) (string
 	}
 	return strings.Replace(buf.String(), lgoExportPrefix, "", -1), nil
 }
+
+func (rn *LgoRunner) RunMagics(ctx core.LgoContext, src string) error {
+	rn.execCount++
+	magicFunctionWithArgs := strings.TrimSpace(src)[1:]
+	magic := magicFunctionWithArgs
+	magicFunctionIndex := strings.Index(magicFunctionWithArgs, " ")
+	var arguments string
+	if magicFunctionIndex != -1 {
+		magic = magicFunctionWithArgs[:magicFunctionIndex]
+		arguments = magicFunctionWithArgs[magicFunctionIndex:]
+	}
+
+	if f, ok := magics.GetRegisteredMagics()[magic]; ok {
+		f(ctx, arguments, rn.Run)
+	} else  {
+		core.LgoPrintln(fmt.Sprintf("UsageError: Line magic function `%%%s` not found.", magic))
+		return  nil
+	}
+
+	return  nil
+}