[augeas-devel] Wildcarded key/value pairs and nested blocks (dovecot lens development)

[Raphaël Pinson]

On Thu, Mar 7, 2013 at 4:33 PM, Serge Smetana <serge.smetana at gmail.com>wrote:

> Hi Raphaël,
>
> Trying to use Build.block_newlines construct
>
>    let any = Rx.no_spaces
>    let value = any . (Rx.space . any)*
>    let commands  = /include|include_try/
>    let block_names =
> /dict|userdb|passdb|protocol|service|plugin|namespace|map/
>    let nested_block_names =
>  /fields|unix_listener|fifo_listener|inet_listener/
>    let keys = Rx.word - commands - block_names - nested_block_names
>

This kind of constructs makes augparse (and run) verrrrrrrrrrrrry slooooow.
It is best to rewrite them as:

   let keys = Rx.word - (commands | block_names | nested_block_names)

which is strictly equivalent, but much faster.



>
>    let entry = [ indent . key keys. eq . (Sep.opt_space . store value)? .
> eol ]
>    let command = [ command_start . key commands . Sep.space . store
> Rx.fspath . eol ]
>
>    let block_args   = Sep.space . store any
>
>    let nested_block = [ indent . key block_names . block_args? .
> Build.block_newlines entry comment . eol ]
>    let block = [ indent . key block_names . block_args? .
> Build.block_newlines (entry|nested_block)* comment . eol]
>
>    let lns = (comment|empty|entry|command|block)*
>
> If I try to compile this I get an exception: ambiguous concatenation
>
>       First regexp: /([
> \t]*)(dict|userdb|passdb|protocol|service|plugin|namespace|map)((([
> \t]+)([^ \t\n]+))?)/
>       Second regexp: /([ \t\n]+\\{([ \t\n]*\n)?)((((([
> \t]*)((dict[.0-9A-Z_a-z-][.0-9A-Z_a-z-]| ...... <long regexp
> here>.....
>
>       'userdb {# {\n}' can be split into
>       'userdb|=| {# {\n}'
>
>      and
>       'userdb {#|=| {\n}'
>

> I guess this is because of optional block_args? in lens definition.
>


Yes, precisely. Spaces must belong only to one side of two concatenated
expressions.



> But my old variant without Build.block* construct works:
>
>   let block_open        = del /[ \t]*\{/ "{"
>   let block_close       = del /\}/ "}"
>
>   .... same as above
>
>   let nested_block =
>        [ indent . key nested_block_names . block_args? . block_open . eol
>        . (entry | empty | comment)*
>        . indent . block_close . eol ]
>
>    let block =
>        [ indent . key block_names . block_args? . block_open . eol
>        . (entry | empty | comment | nested_block )*
>       . indent . block_close . eol ]
>


Build.block_newlines allows things like

    unix_listener {# {\n}

where "# {\n" should be a comment.

However, block_args? allows *any* character (including "#" and "{") to be
present between the key and the opening bracket. I think block_args should
be refined to only allow the characters you need.


Regards,

-- 
Raphaël Pinson
Administrateur Systèmes & Réseaux
Camptocamp France
Savoie Technolac
BP 352
48, avenue du Lac du Bourget
73372 Le Bourget du Lac, Cedex
www.camptocamp.com
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