Idea: Preserve matchdata in rules

[avdi]

Here's part of a rule I just wrote the other day:

stampfile_pattern = %r"^members/(?<email>.*)/\d{2}-(?<step>\w+).timestamp$"
rule stampfile_pattern do |t|
  match           = stampfile_pattern.match(t.name)
  email           = match[:email]
  step            = match[:step]
  # ...
end

Notice how, after it matches, I have to re-apply the regex inside the rule definition in order to pull out named matchdata.

I was thinking of introducing something like this as an alternative:

stampfile_pattern = %r"^members/(?<email>.*)/\d{2}-(?<step>\w+).timestamp$"
rule stampfile_pattern do |t|
  email           = t.matchdata[:email]
  step            = t.matchdata[:step]
  # ...
end

Before I dive in, what do you think? And is there another way to accomplish this that I've missed?

[drbrain]

I think this would be a nice addition.

I don't think there's a way to accomplish this without adding the feature to the rule.

I've not used a rule without dependencies, it gets triggered by a separate task that depends on the output (regexp)?

[avdi]

I don't think there's a way to accomplish this without adding the feature to the rule.

Yeah, that's what I was thinking. I feel like it makes sense, since the task object already has the concrete t.name that matched, to also have the matchdata.

I've not used a rule without dependencies, it gets triggered by a separate task that depends on the output (regexp)?

Yep.

[avdi]

I've also thought about this:

rule %r"^members/(?<email>.*)/\d{2}-(?<step>\w+).timestamp$" => 
  "members/%{email}/some-input-file" do |t|
  email           = t.matchdata[:email]
  step            = t.matchdata[:step]
  # ...
end

I.e. adding the ability to substitute in backreferences in the rule source. Currently, rule sources suffer from the same problem as the rule body: if you want to reference regex matchdata, you have to use a lambda as the dependency and re-apply the regex.

[yeban]

I stumbled upon this issue looking for how to access matchdata inside a rule. This would be a great addition, imho.

[avdi]

Oh hey, thanks for reminding me.

…

On Fri, Dec 2, 2016 at 9:07 AM, Anurag Priyam ***@***.***> wrote: I stumbled upon this issue looking for how to access matchdata inside a rule. This would be a great addition, imho. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#141 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAD1vT-M-mathKpiMBZoe60ozhgaAU8ks5rECYkgaJpZM4I20fQ> .