Improved compile errors

ph7.go

@@ -56,22 +56,28 @@ type Error struct {
 // TODO create a CompileError that contains the error log text
 
 func newError(code C.int) error {
-	if code != C.PH7_OK {
+	if code == C.PH7_OK {
+		return nil
+	}
 	return Error{
 		Code: ResultCode(code),
 	}
-	}
-	return nil
 }
 
 func (e Error) Error() string {
-	return fmt.Sprintf("ph7: %s", e.Code)
+	return fmt.Sprintf("ph7: %s", e.Code.String())
+}
+
+type CompileError struct {
+	Msg string
+}
+
+func (e CompileError) Error() string {
+	return fmt.Sprintf("ph7 compile error: %s", e.Msg)
 }
 
 type Engine C.ph7
 
-// TODO strip off the enclosing struct if possible after wrapping all engine methods.
-
 func NewEngine() (*Engine, error) {
 	var cengine *C.ph7
 	result := C.ph7_init(&cengine)
@@ -96,6 +102,23 @@ func (e *Engine) ErrLog() (string, error) {
 
 // TODO All the ph7_config verbs
 
+func (e *Engine) compileError(code C.int) error {
+	switch code {
+	case C.PH7_OK:
+		return nil
+	case C.PH7_COMPILE_ERR:
+		errLog, errLogErr := e.ErrLog()
+		if errLogErr != nil || errLog == "" {
+			return newError(code)
+		}
+		return CompileError{
+			Msg: errLog,
+		}
+	default:
+		return newError(code)
+	}
+}
+
 func (e *Engine) Compile(source []byte, phpOnly bool) (*VM, error) {
 	csource := C.CBytes(source)
 	defer C.free(csource)
@@ -104,7 +127,7 @@ func (e *Engine) Compile(source []byte, phpOnly bool) (*VM, error) {
 		flags |= C.PH7_PHP_ONLY
 	}
 	var cvm *C.ph7_vm
-	err := newError(C.ph7_compile_v2((*C.ph7)(e), (*C.char)(csource), C.int(len(source)), &cvm, flags))
+	err := e.compileError(C.ph7_compile_v2((*C.ph7)(e), (*C.char)(csource), C.int(len(source)), &cvm, flags))
 	if err != nil {
 		return nil, err
 	}

ph7_test.go

@@ -2,6 +2,7 @@ package ph7_test
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"testing"
 
@@ -63,10 +64,10 @@ func TestCompileError(t *testing.T) {
 
 	_, err = engine.Compile([]byte("<?php 1234 echo 'Hello world!'; ?>"), false)
 	mustFail(t, err)
-	msg, err := engine.ErrLog()
-	mustSucceed(t, err)
-	if msg == "" {
-		t.Fatalf("expected error message, got nothing")
+	var target ph7.CompileError
+	isCompileError := errors.As(err, &target)
+	if !isCompileError || target.Msg == "" {
+		t.Fatalf("expected compile error, got %#v", err)
 	}
 }