From 0afe1f78a51990d7849a11339fe9c5af06165bd4 Mon Sep 17 00:00:00 2001
From: Serge Petrenko <sergepetrenko@tarantool.org>
Date: Thu, 12 Aug 2021 22:50:19 +0300
Subject: [PATCH] lua: introduce table.equals method
Introduce table.equals for comparing tables.
The method respects __eq metamethod, if provided.
Needed-for #5894
@TarantoolBot document
Title: lua: new method table.equals
Document the new lua method table.equals
It compares two tables deeply. For example:
```
tarantool> t1 = {a=3}
---
...
tarantool> t2 = {a=3}
---
...
tarantool> t1 == t2
---
- false
...
tarantool> table.equals(t1, t2)
---
- true
...
```
The method respects the __eq metamethod. When both tables being compared
have the same __eq metamethod, it's used for comparison (just like this
is done in Lua 5.1)
---
.../unreleased/introduce-table-equals.md | 4 ++
src/lua/table.lua | 29 +++++++++++
test/app-tap/table.test.lua | 49 ++++++++++++++++++-
3 files changed, 81 insertions(+), 1 deletion(-)
create mode 100644 changelogs/unreleased/introduce-table-equals.md
diff --git a/changelogs/unreleased/introduce-table-equals.md b/changelogs/unreleased/introduce-table-equals.md
new file mode 100644
index 0000000000..282b56c43b
--- /dev/null
+++ b/changelogs/unreleased/introduce-table-equals.md
@@ -0,0 +1,4 @@
+## feature/lua
+
+* Introduce method `table.equals`. It compares 2 tables by value and respects
+ `__eq` metamethod.
diff --git a/src/lua/table.lua b/src/lua/table.lua
index 8fa9b876ac..edd60d1be5 100644
--- a/src/lua/table.lua
+++ b/src/lua/table.lua
@@ -57,6 +57,34 @@ local function table_shallowcopy(orig)
return copy
end
+--- Compare two lua tables
+-- Supports __eq metamethod for comparing custom tables with metatables
+-- @function equals
+-- @return true when the two tables are equal (false otherwise).
+local function table_equals(a, b)
+ if type(a) ~= 'table' or type(b) ~= 'table' then
+ return type(a) == type(b) and a == b
+ end
+ local mta = getmetatable(a)
+ local mtb = getmetatable(b)
+ -- Let Lua decide what should happen when at least one of the tables has a
+ -- metatable.
+ if mta and mta.__eq or mtb and mtb.__eq then
+ return a == b
+ end
+ for k, v in pairs(a) do
+ if not table_equals(v, b[k]) then
+ return false
+ end
+ end
+ for k, _ in pairs(b) do
+ if not a[k] then
+ return false
+ end
+ end
+ return true
+end
+
-- table library extension
local table = require('table')
-- require modifies global "table" module and adds "clear" function to it.
@@ -65,3 +93,4 @@ require('table.clear')
table.copy = table_shallowcopy
table.deepcopy = table_deepcopy
+table.equals = table_equals
diff --git a/test/app-tap/table.test.lua b/test/app-tap/table.test.lua
index 60c095fdfc..ae6fdfa2d1 100755
--- a/test/app-tap/table.test.lua
+++ b/test/app-tap/table.test.lua
@@ -8,7 +8,7 @@ yaml.cfg{
encode_invalid_as_nil = true,
}
local test = require('tap').test('table')
-test:plan(31)
+test:plan(44)
do -- check basic table.copy (deepcopy)
local example_table = {
@@ -223,4 +223,51 @@ do -- check usage of not __copy metamethod on second level + shallow
)
end
+do -- check table.equals
+ test:ok(table.equals({}, {}), "table.equals for empty tables")
+ test:is(table.equals({}, {1}), false, "table.equals with one empty table")
+ test:is(table.equals({1}, {}), false, "table.equals with one empty table")
+ test:is(table.equals({key = box.NULL}, {key = nil}), false,
+ "table.equals for box.NULL and nil")
+ test:is(table.equals({key = nil}, {key = box.NULL}), false,
+ "table.equals for box.NULL and nil")
+ local tbl_a = {
+ first = {
+ 1,
+ 2,
+ {},
+ },
+ second = {
+ a = {
+ {'something'},
+ },
+ b = 'something else',
+ },
+ [3] = 'some value',
+ }
+ local tbl_b = table.deepcopy(tbl_a)
+ local tbl_c = table.copy(tbl_a)
+ test:ok(table.equals(tbl_a, tbl_b), "table.equals for complex tables")
+ test:ok(table.equals(tbl_a, tbl_c),
+ "table.equals for shallow copied tables")
+ tbl_c.second.a = 'other thing'
+ test:ok(table.equals(tbl_a, tbl_c),
+ "table.equals for shallow copied tables after modification")
+ test:is(table.equals(tbl_a, tbl_b), false, "table.equals does a deep check")
+ local mt = {
+ __eq = function(a, b) -- luacheck: no unused args
+ return true
+ end}
+ local tbl_d = setmetatable({a = 15}, mt)
+ local tbl_e = setmetatable({b = 2, c = 3}, mt)
+ test:ok(table.equals(tbl_d, tbl_e), "table.equals respects __eq")
+ test:is(table.equals(tbl_d, {a = 15}), false,
+ "table.equals when metatables don't match")
+ test:is(table.equals({a = 15}, tbl_d), false,
+ "table.equals when metatables don't match")
+ local tbl_f = setmetatable({a = 15}, {__eq = function() return true end})
+ test:is(table.equals(tbl_d, tbl_f), false,
+ "table.equals when metatables don't match")
+end
+
os.exit(test:check() == true and 0 or 1)
--
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