Array of Tables Whitespace Syntax Clarification Query ("[[" vs "[ [")

[TommyJC]

Hello,

I was just curious about lexing an array of tables. The standard that I saw here:

https://toml.io/en/v1.0.0#array-of-tables

states that an array of tables only requires double brackets, but unlike the boolean section:

https://toml.io/en/v1.0.0#boolean

that strictly states "Always lowercase." forbidding boolean value attempts such as foo = True, there doesn't appear to be any such restrictions such as "The brackets must be adjacent."

Therefore, I just wanted to know if the following are (or should be) permitted alternatives to writing an array of tables.

[[ WhenDoingPushUps ] ]
[ [ "Tell Yourself" ] ]
[ [AnotherOne] ]
[ [AnotherOne] ]

After lexing those array of tables, in my mind, they end up looking like this:

[[WhenDoingPushUps]]
[["Tell Yourself"]]
[[AnotherOne]]
[[AnotherOne]]

Just a quick test that I did:

Python Tomli Module

When using python's tomli module (python 3.9 with tomli installed via pip in a virtualenv), it strictly requires that the square brackets are adjacent to each other:

[ [ ThisOne ]]
[[ "And This One Are Unacceptable" ] ]

Please let me know if I was looking at the wrong document and this information is documented elsewhere.

[eksortso]

The section that you link to is right, but the devil's in the details. The standard specifies in its formal grammar, toml.abnf (linked to at the bottom of the page), that the double brackets in an array table must be adjacent; no whitespace is permitted between the left brackets or between the right brackets. So [[ThisIsValid]] and [[ "So's This." ]] But the whitespace between the same brackets in your examples makes those invalid.

I posit that it's a lot more obvious and minimal if the brackets are constrained this way, not to mention simpler for parsers to work with. For a simple array key, just look for the next pair of right brackets. For quoted array keys, look for them after the key string.

Personally, I would not want to change this, unless more significant changes to the syntax were being discussed. But that's just been my experience talking.

[TommyJC]

Ah, I didn't see the ABNF, thank you!