Fix patching value with nil

library/lua/test_util/mock.lua

@@ -5,15 +5,15 @@ local mock = mkmodule('test_util.mock')
 Usage:
     patch(table, key, value, callback)
     patch({
-        [{table, key}] = value,
-        [{table2, key2}] = value2
+        {table, key, value},
+        {table2, key2, value2}
     }, callback)
 ]]
 function mock.patch(...)
     local args = {...}
     if #args == 4 then
         args = {{
-            [{args[1], args[2]}] = args[3]
+            {args[1], args[2], args[3]}
         }, args[4]}
     end
     if #args ~= 2 then
@@ -22,15 +22,15 @@ function mock.patch(...)
 
     local callback = args[2]
     local patches = {}
-    for k, v in pairs(args[1]) do
+    for _, v in ipairs(args[1]) do
         local p = {
-            table = k[1],
-            key = k[2],
-            new_value = v,
+            table = v[1],
+            key = v[2],
+            new_value = v[3],
         }
         p.old_value = p.table[p.key]
         -- no-op to ensure that the value can be restored by the finalizer below
-        p.table[p.key] = p.table[p.key]
+        p.table[p.key] = p.old_value
         table.insert(patches, p)
     end
 

test/library/test_util/mock.lua

@@ -33,8 +33,8 @@ function test.patch_multiple()
     expect.eq(test_table.func1(), 1)
     expect.eq(test_table.func2(), 2)
     mock.patch({
-        [{test_table, 'func1'}] = function() return 3 end,
-        [{test_table, 'func2'}] = function() return 4 end,
+        {test_table, 'func1', function() return 3 end},
+        {test_table, 'func2', function() return 4 end},
     }, function()
         expect.eq(test_table.func1(), 3)
         expect.eq(test_table.func2(), 4)
@@ -43,3 +43,50 @@ function test.patch_multiple()
     expect.eq(test_table.func2(), 2)
 end
 
+function test.patch_nil_old_value()
+    local t = {}
+    mock.patch(t, 1, 2, function()
+        expect.eq(t[1], 2)
+    end)
+    expect.eq(t[1], nil)
+    expect.eq(#t, 0)
+end
+
+function test.patch_nil_new_value()
+    local t = {2}
+    mock.patch(t, 1, nil, function()
+        expect.eq(t[1], nil)
+        expect.eq(#t, 0)
+    end)
+    expect.eq(t[1], 2)
+end
+
+function test.patch_nil_key()
+    local called = false
+    expect.error_match('table index is nil', function()
+        mock.patch({}, nil, 'value', function()
+            called = true
+        end)
+    end)
+    expect.false_(called)
+end
+
+function test.patch_nil_table()
+    local called = false
+    expect.error(function()
+        mock.patch(nil, 1, 2, function()
+            called = true
+        end)
+    end)
+    expect.false_(called)
+end
+
+function test.patch_complex_key()
+    local key = {'key'}
+    local t = {[key] = 'value'}
+    expect.eq(t[key], 'value')
+    mock.patch(t, key, 2, function()
+        expect.eq(t[key], 2)
+    end)
+    expect.eq(t[key], 'value')
+end