1

So Doctrine annotations are based on JSON but as PHP arrays allow for dangling commas Drupal people are much used to this and to be honest, it's much easier to edit

(
  "foo" => "bar",
  "foo1" => "bar1",
)

so that the rows can be switched, another row added etc than if that comma after bar1 were missing.

So I am trying to patch Doctrine to allow for this. The maintainer claims

you are mixing grammar rules by checking a token that is not part of "Values", but its parent, "Annotation".

And he is right. So, we are looking for a better grammar.

Annotation     ::= "@" AnnotationName ["(" [Values] ")"]
Values ::= Array | Value {"," Value}*

How would you allow for a trailing comma in Values?

chx
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2 Answers2

4

The modified grammar is not LL(1) anymore. As a consequence the simple recursive descent parser implemented by Doctrine requires backtracking.

In this case, you need to make sure that ::Value() can backtrack, ie. trigger an exception and reset the parsing to the position it was in before entering ::Value(). You catch this exception and just ignore it in ::Values() as soon as you already have one valid value.

That requires to be able to seek in the lexer, and I don't know how practical it is. AbstractLexer is quite a bit weird.

Edit: The easiest way forward would be to keep the grammar in a LL(1) form. One way of doing that is to move the parenthesis inside Values:

Values ::= "(" [Array | Value {"," Value}* [","] ] ")"
Damien Tournoud
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2

To add an optional comma at the end we can use the [] notation:

Annotation     ::= "@" AnnotationName ["(" [Values] ")"]
Values ::= Array | Value {"," Value}* [","]
klausi
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