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Robo

This is very alpha software. I'll probably change how the entire thing works, not to far in the future.

Robo is an automation tool akin to make. Unlike make, it does not use filesystem paths and modification time to determine which targets need to be rebuilt. Instead users are allowed to leverage the full power of Prolog to define recipes and their dependencies as well as the conditions under which a target needs to be rebuilt.

Building

Robo is based on SWI-Prolog and expects swipl to be available on the system.

You can use robo.pl directly, or build a pseudo-binary via:

$ ./robo build

Robofile Predicates

recipe/1

Every recipe/1 matching the goal gets executed, unless there's a matching cancel/1. A target is considered successful if at least one matching recipe/1 succeeds.

For example:

% Robofile
recipe(default) :- write("Hello,").
recipe(default) :- fail.
recipe(default) :- write(" World!\n").

$ robo default succeeds and prints Hello, World!.

cancel/1

For any given target, if there is a matching cancel/1, then that target succeeds unconditionally.

For example:

% Robofile
recipe(default) :- write("Executed default\n").
cancel(default).

$ robo default succeeds, but does not print anything, because recipe(default) did not run.

depend/2

Declares a dependency from one target to another. Dependencies of a target are solved before the target itself is solved.

For example:

% Robofile
recipe(print:String) :- write(String).
depend(default, print:"A ").
depend(default, print:"B ").
recipe(default) :- write(" C\n")

$ robo default succeeds and prints A B C.

target/1

Defines that a target exists. When using wildcard goals (robo -G print:_) robo is sometimes unable to determine that a target exists. target/1 is used to declare the existance of a target that may not have any exactly matching recipe/1.

For example:

% Robofile
recipe(print:String) :- write(String).

$ robo -G print:_ fails, because there are no known targets that match print:_

% Robofile
recipe(print:String) :- write(String).
target(print:"Hello, ").
target(print:"World!\n").

$ robo -G print:_ succeeds and prints Hello, World!

hidden/1

Unimplemented Prevents matching targets from being requested from the command-line.

TODO

  • ./2 makes file paths rather painful.
  • Should main share the Solved state between goals, when the user has requested multiple goals?
  • Should every matching recipe be called, for a given goal?
  • stringify from foo/bar/baz
  • should child cancel/1 run before their dependencies do?
  • How should cancellation work? Right now, if any cancel(Goal) succeeds then that goal is considered canceled. However, we could require that every clause succeed at least once, maybe?
  • should cancel/1 be replaced with compel/1? Targets would only execute if either any of their dependencies execute or there is a matching compel/1? But what about order-only dependencies found in Makefiles?
  • default targets, like in Makefiles
  • Make terminology consistent. Are they targets, goals, queries, what?