From ce4babb19289f952cf440b30b38ba127e78e810a Mon Sep 17 00:00:00 2001
From: Niels Martin Hansen <nielsm@aegisub.org>
Date: Wed, 30 Jun 2010 00:36:25 +0000
Subject: [PATCH] Update table.copy_deep function to correctly handle
 self-referencing tables and tables with circular references. Doesn't handle
 tables with meta-tables overriding regular field get/set behaviour but that
 isn't intended either way. Also add a test of this.

Originally committed to SVN as r4645.
---
 aegisub/automation/include/utils-auto4.lua    | 29 ++++++++++-----
 .../tests/test-tablecopy-recursive.lua        | 37 +++++++++++++++++++
 2 files changed, 56 insertions(+), 10 deletions(-)
 create mode 100644 aegisub/automation/tests/test-tablecopy-recursive.lua

diff --git a/aegisub/automation/include/utils-auto4.lua b/aegisub/automation/include/utils-auto4.lua
index 161b8edb8..368163162 100644
--- a/aegisub/automation/include/utils-auto4.lua
+++ b/aegisub/automation/include/utils-auto4.lua
@@ -1,5 +1,5 @@
 --[[
- Copyright (c) 2005-2006, Niels Martin Hansen, Rodrigo Braz Monteiro
+ Copyright (c) 2005-2010, Niels Martin Hansen, Rodrigo Braz Monteiro
  All rights reserved.
 
  Redistribution and use in source and binary forms, with or without
@@ -39,21 +39,30 @@ end
 copy_line = table.copy
 
 -- Make a deep copy of a table
--- This will do infinite recursion if there's any circular references. (Eg. if you try to copy _G)
+-- Retains equality of table references inside the copy and handles self-referencing structures
 function table.copy_deep(srctab)
 	-- Table to hold subtables already copied, to avoid circular references causing infinite recursion
 	local circular = {}
 	local function do_copy(oldtab)
-		local newtab = {}
-		for key, val in pairs(newtab) do
-			if type(val) == "table" then
-				if not circular[val] then
-					circular[val] = do_copy(val)
+		-- Check if we know the source already
+		if circular[oldtab] then
+			-- Use already-made copy
+			return circular[oldtab]
+		else
+			-- Prepare a new table to copy into
+			local newtab = {}
+			-- Register it as known
+			circular[oldtab] = newtab
+			-- Copy fields
+			for key, val in pairs(oldtab) do
+				-- Copy tables recursively, everything else normally
+				if type(val) == "table" then
+					newtab[key] = do_copy(val)
+				else
+					newtab[key] = val
 				end
-				newtab[key] = circular[val]
-			else
-				newtab[key] = val
 			end
+			return newtab
 		end
 	end
 	return do_copy(srctab)
diff --git a/aegisub/automation/tests/test-tablecopy-recursive.lua b/aegisub/automation/tests/test-tablecopy-recursive.lua
new file mode 100644
index 000000000..3a7fa98bb
--- /dev/null
+++ b/aegisub/automation/tests/test-tablecopy-recursive.lua
@@ -0,0 +1,37 @@
+script_name = "Test table.copy_deep"
+script_description = "Tests the Auto4 Lua utils.lua table.copy_deep function"
+script_author = "Niels Martin Hansen"
+
+include "utils.lua"
+
+function test_tablecopy_deep()
+	local function test_table(tab, desc)
+		local l = aegisub.log
+		l("--- %15s -------------\n", desc)
+		l("tab.a = %d\n", tab.a)
+		l("type(tab.b) = %s\n", type(tab.b))
+		l("tab.b.a = %s\n", tab.b.a)
+		l("tab.c==tab.b ? %d\n", (tab.c==tab.b) and 1 or 0)
+		l("type(tab.b.b) = %s\n", type(tab.b.b))
+		l("type(tab.d) = %s\n", type(tab.d))
+		l("tab.d.a == tab.d ? %d\n", (tab.d.a==tab.d) and 1 or 0)
+		l("tab.e == tab ? %d\n", (tab.e==tab) and 1 or 0)
+		l("\n")
+	end
+	
+	local orgtab = {}
+	orgtab.a = 1
+	orgtab.b = {}
+	orgtab.b.a = "hi"
+	orgtab.c = orgtab.b
+	orgtab.c.b = test_table
+	orgtab.d = {}
+	orgtab.d.a = orgtab.d
+	orgtab.e = orgtab
+	test_table(orgtab, "Original table")
+	
+	local cpytab = table.copy_deep(orgtab)
+	test_table(cpytab, "Copied table")
+end
+
+aegisub.register_macro("TEST table.copy_deep", "", test_tablecopy_deep)