Issue #15068 has been updated by James Turnbull.

Project changed from Puppet DSL to Puppet
Category deleted (Puppet DSL)


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Bug #15068: Promises or Futures for Bound Data Values
https://projects.puppetlabs.com/issues/15068#change-69368

Author: Pieter van de Bruggen
Status: Needs More Information
Priority: Normal
Assignee: Pieter van de Bruggen
Category: 
Target version: 
Affected Puppet version: 
Keywords: 
Branch: 


A commonly expressed desire is the ability to "lookup" values from a named 
resource, and use them as a value.

One proposed syntax looks like this:

    File['/etc/hosts'].owner

There are a number of potential data sources implied by this feature:

  * Data expressed explicitly elsewhere in the manifest.
  * Data expressed implicitly (defaults) elsewhere in the manifest.
  * Data from the pre-execution state of a managed resource on the target 
system.
  * Data from the post-execution state of a managed resource on the target 
system.
  * Data from the pre-execution state of an unmanaged resource on the target 
system.
  * Data from the post-execution state of an unmanaged resource on the target 
system.
  * Data from the pre-execution state of a managed resource on a remote system.
  * Data from the post-execution state of a managed resource on a remote system.
  * Data from the state of an managed resource on a remote system.
  * Data from the state of an unmanaged resource on a remote system.

Done properly, this could easily create implicit relationships between data 
sources and promise consumers, and could potentially be an elegant solution to 
the cross-node dependency problem.  The biggest hinderances to this come 
managing expectations (managed resources vs. unmanaged resources), and the 
difficulty in expressing the temporal context to fetch data from.

A mechanism like this would soon afterwards demand a mechanism to expose 
properties (static, bound, and computed) from classes and defined types.

via 
[puppet-users](https://groups.google.com/forum/?fromgroups#!topic/puppet-users/KqJx9hPvb4g)


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