From 7a18b4e379e966a82dc02f664b625368bce0332a Mon Sep 17 00:00:00 2001
From: Kaylee Hirsch <emperorshishire@gmail.com>
Date: Mon, 29 Aug 2022 20:33:53 -0700
Subject: [PATCH] Add ForEachWithError to LTable

Provide a break capable, as well as error capable implementation of
ForEach, allowing for early short-circuit and deep logging of error
messages.  Implement it underneath the current version, keeping only one
code path for maintenance purposes, but allow multiple ways of calling
this functionality as needed.
---
 table.go      | 23 ++++++++++++++++++++---
 table_test.go | 27 +++++++++++++++++++++++++++
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/table.go b/table.go
index ddf14dd8..b655edc2 100644
--- a/table.go
+++ b/table.go
@@ -324,27 +324,44 @@ func (tb *LTable) RawGetString(key string) LValue {
 
 // ForEach iterates over this table of elements, yielding each in turn to a given function.
 func (tb *LTable) ForEach(cb func(LValue, LValue)) {
+	tb.ForEachWithError(func(key, value LValue) error {
+		cb(key, value)
+		return nil
+	})
+}
+
+// ForEachWithError iterates over this table of elements, yielding each in turn
+// to a given function.  If it receives a non-nil error from its callback, it
+// breaks and passes it back to its caller.
+func (tb *LTable) ForEachWithError(cb func(LValue, LValue) error) error {
 	if tb.array != nil {
 		for i, v := range tb.array {
 			if v != LNil {
-				cb(LNumber(i+1), v)
+				if err := cb(LNumber(i+1), v); err != nil {
+					return err
+				}
 			}
 		}
 	}
 	if tb.strdict != nil {
 		for k, v := range tb.strdict {
 			if v != LNil {
-				cb(LString(k), v)
+				if err := cb(LString(k), v); err != nil {
+					return err
+				}
 			}
 		}
 	}
 	if tb.dict != nil {
 		for k, v := range tb.dict {
 			if v != LNil {
-				cb(k, v)
+				if err := cb(k, v); err != nil {
+					return err
+				}
 			}
 		}
 	}
+	return nil
 }
 
 // This function is equivalent to lua_next ( http://www.lua.org/manual/5.1/manual.html#lua_next ).
diff --git a/table_test.go b/table_test.go
index 6acbbb2c..50ffefc4 100644
--- a/table_test.go
+++ b/table_test.go
@@ -1,6 +1,7 @@
 package lua
 
 import (
+	"fmt"
 	"testing"
 )
 
@@ -231,3 +232,29 @@ func TestTableForEach(t *testing.T) {
 		}
 	})
 }
+
+func TestTableForEachWithError(t *testing.T) {
+	tbl := newLTable(0, 0)
+	tbl.Append(LNumber(1))
+	tbl.Append(LNumber(2))
+	tbl.Append(LNumber(3))
+	tbl.Append(LNil)
+	tbl.Append(LNumber(5))
+
+	tbl.RawSetH(LString("a"), LString("a"))
+	tbl.RawSetH(LString("b"), LString("b"))
+	tbl.RawSetH(LString("c"), LString("c"))
+
+	tbl.RawSetH(LTrue, LString("true"))
+	tbl.RawSetH(LFalse, LString("false"))
+
+	testError := fmt.Errorf("test error")
+	runCount := 0
+	err := tbl.ForEachWithError(func(key, value LValue) error {
+		runCount += 1
+		return testError
+	})
+
+	errorIfNotEqual(t, testError, err)
+	errorIfNotEqual(t, 1, runCount)
+}