Dependency.expand_dependencies

Move Formula.expand_dependencies into the Dependency class, and extend
it to allow arbitrary filters to be applied when enumerating deps.

When supplied with a block, expand_dependencies will yield a [dependent,
dependency] pair for each dependency, allowing callers to filter out
dependencies that may not be applicable or useful in a given situation.

Deps can be skipped by simple calling Dependency.prune in the block,
e.g.:

  Dependency.expand_dependencies do |f, dep|
    Dependency.prune if dep.to_formula.installed?
  end

The return value of the method is the filtered list.

If no block is supplied, a default filter that omits optional or
recommended deps based on what the dependent formula has requested is
applied.

Formula#recursive_dependencies is now implemented on top of this,
allowing FormulaInstaller to exact detailed control over what deps are
installed. `brew missing` and `brew upgrade` can learn to use this to
apply the installed options set when expanding dependencies.

Move Formula.expand_deps and Formula#recursive_deps into compat, because
these methods do not respect the new optional and recommended tags and
thus should no longer be used.

1 files changed, 26 insertions, 0 deletions

diff --git a/Library/Homebrew/dependencies.rb b/Library/Homebrew/dependencies.rb
index dd51a2131..5762ac82e 100644
--- a/Library/Homebrew/dependencies.rb
+++ b/Library/Homebrew/dependencies.rb
@@ -177,6 +177,32 @@ class Dependency
   def requested?
     ARGV.formulae.include?(to_formula) rescue false
   end
+
+  # Expand the dependencies of f recursively, optionally yielding
+  # [f, dep] to allow callers to apply arbitrary filters to the list.
+  # The default filter, which is used when a block is not supplied,
+  # omits optionals and recommendeds based on what the dependent has
+  # asked for.
+  def self.expand(dependent, &block)
+    dependent.deps.map do |dep|
+      prune = catch(:prune) do
+        if block_given?
+          yield dependent, dep
+        elsif dep.optional? || dep.recommended?
+          Dependency.prune unless dependent.build.with?(dep.name)
+        end
+      end
+
+      next if prune
+
+      expand(dep.to_formula, &block) << dep
+    end.flatten.compact.uniq
+  end
+
+  # Used to prune dependencies when calling expand_dependencies with a block.
+  def self.prune
+    throw(:prune, true)
+  end
 end
 
 # A base class for non-formula requirements needed by formulae.