Assemblage.Action

Build action.

An action determines how to output a list of build products from a list of existing input products using a sequence of commands.

Given a notion of product identity (e.g. hash, timestamp, etc.) an action defines a pure function from its input to its outputs, it is assumed that identical inputs yield identical outputs.

In order to be productive it is important to understand the following terminology. With respect to a project:

A product is any existing file in the Assemblage.Conf.root_dir hierarchy.
A source product is a product for which there exists no action to create it; typically the source code you write, a product from your brain.
A build product is a product that is output from a build action.
An input product is a product that is used as input to a build action, this can be a source product or a build product.
An output product is synonym with build product

A build driver is an assemblage driver that given a specification of the project's products yielded by a configuration ensures that all the products exists and are up-to-date according to the project's actions.

FIXME. The following need to clarified

Empty inputs, empty outputs, empty cmds or any combination there of.
Assemblage.Part.file uses empty outputs and empty inputs. This allows Assemblage.Dir which works on products regardless (i.e., input and output) to be made aware of their existence.
Assemblage.Run use build actions but they are not build per se as we run the command inconditionally.
The model is too weak. How need a way to account for ocamldep, gcc -MD -MP, etc.

The type for build actions.

v ctx inputs outputs cmds is the action that given the existence of inputs creates outputs using the sequence of command cmds. ctx defaults to Ctx.empty, inputs and outputs to the empty list. log is a high-level logging string about the action that may be used by drivers when the action is invoked.

Warning. To ensure determinism and parallelism correctness cmds must ensure that it only reads from the inputs and solely writes to outputs.

ctx a is a's context.

inputs a is the list of products input by a's action.

outputs a is the list of products output by a's action.

cmds a is a's commands to generate outputs from the inputs.

log a is a's high-level logging string (if any).

products a is inputs a @ outputs a but tail recursive.

symlink has an action action src dst that links src to dst using Assemblage.Acmd.ln_rel.

list_inputs l is the list of inputs of the actions in l. Ordered but may contain duplicates.

list_outputs l is the list of outputs of the actions in l. Ordered but may contain duplicates.

list_products l is list_inputs l @ list_outputs l but tail-recursive.

Module Assemblage.Action

Build actions

Built-in actions

Action lists