[Tarantool-patches] [PATCH v3 2/9] lua: built-in module datetime

[Safin Timur]

On 06.08.2021 4:30, Oleg Babin wrote:
> 
> On 06.08.2021 03:23, Safin Timur wrote:
>>
>> i.e. whenever we see not datetime or interva value datetime_cmp return 
>> nil, and all comparisons always return false. Please give me know if 
>> that's incorrect scenario and we should raise exception. This was the 
>> way Oleg Bain has requested it to behave. (return false for bogus data)
>>
> Hi! Seems you understood me wrong. It was only about equal comparison.
> 
> ```
> 
> tarantool> uuid.new() == newproxy()
> ---
> - false
> ...
> 
> tarantool> uuid.new() > newproxy()
> ---
> - error: '[string "return require(''uuid'').new() > newproxy()"]:1: 
> incorrect value
>      to convert to uuid as 1 argument'
> ...
> 
> ```
> 
> 
> However, currently I see that decimal have a bit different behaviour and 
> raises always:
> 
> ```
> 
> tarantool> decimal.new(1) == newproxy()
> ---
> - error: '[string "return decimal.new(1) == newproxy()"]:1: expected 
> decimal, number
>      or string as 2 argument'
> ...
> 
> tarantool> decimal.new(1) > newproxy()
> ---
> - error: '[string "return decimal.new(1) > newproxy()"]:1: expected 
> decimal, number
>      or string as 1 argument'
> ...
> 
> ```
> 
> 
> IMO, the first case is better because we can check that two lua built-in 
> types
> 
> are equal but can't compare them.
> 
> ```
> 
> tarantool> {} == 'string'
> ---
> - false
> ...
> 
> tarantool> {} > 'string'
> ---
> - error: '[string "return {} > ''string''"]:1: attempt to compare string 
> with table'
> ...
> 
> ```
> 
> 

Now, that looks more or less consistent, will do it such!

```
tarantool> date = require 'datetime'
---
...

tarantool> T = date('1970-01-01')
---
...

tarantool> T == false
---
- false
...

tarantool> T == true
---
- false
...

tarantool> T < false
---
- error: '[string "return T < false"]:1: incompatible types for comparison'
...

tarantool> T <= 'string'
---
- error: '[string "return T <= ''string''"]:1: incompatible types for 
comparison'
...
```

Patch is simple though
==============================================================
diff --git a/src/lua/datetime.lua b/src/lua/datetime.lua
index 0bc86c9f3..509a2981f 100644
--- a/src/lua/datetime.lua
+++ b/src/lua/datetime.lua
@@ -245,12 +245,12 @@ end

  local function datetime_lt(lhs, rhs)
      local rc = datetime_cmp(lhs, rhs)
-    return rc ~= nil and rc < 0 or false
+    return rc ~= nil and rc < 0 or error('incompatible types for 
comparison', 2)
  end

  local function datetime_le(lhs, rhs)
      local rc = datetime_cmp(lhs, rhs)
-    return rc ~= nil and rc <= 0 or false
+    return rc ~= nil and rc <= 0 or  error('incompatible types for 
comparison', 2)
  end

  local function datetime_serialize(self)
==============================================================

Do we want to use that approach here?

Thanks,
Timur