1 files changed, 136 insertions, 0 deletions
diff --git a/Library/Homebrew/test/dependency_expansion_spec.rb b/Library/Homebrew/test/dependency_expansion_spec.rb
new file mode 100644
index 000000000..f955237a9
--- /dev/null
+++ b/Library/Homebrew/test/dependency_expansion_spec.rb
@@ -0,0 +1,136 @@
+require "dependency"
+
+describe Dependency do
+  def build_dep(name, tags = [], deps = [])
+    dep = described_class.new(name.to_s, tags)
+    allow(dep).to receive(:to_formula).and_return(double(deps: deps, name: name))
+    dep
+  end
+
+  let(:foo) { build_dep(:foo) }
+  let(:bar) { build_dep(:bar) }
+  let(:baz) { build_dep(:baz) }
+  let(:qux) { build_dep(:qux) }
+  let(:deps) { [foo, bar, baz, qux] }
+  let(:formula) { double(deps: deps, name: "f") }
+
+  describe "::expand" do
+    it "yields dependent and dependency pairs" do
+      i = 0
+      described_class.expand(formula) do |dependent, dep|
+        expect(dependent).to eq(formula)
+        expect(deps[i]).to eq(dep)
+        i += 1
+      end
+    end
+
+    it "returns the dependencies" do
+      expect(described_class.expand(formula)).to eq(deps)
+    end
+
+    it "prunes all when given a block with ::prune" do
+      expect(described_class.expand(formula) { described_class.prune }).to be_empty
+    end
+
+    it "can prune selectively" do
+      deps = described_class.expand(formula) do |_, dep|
+        described_class.prune if dep.name == "foo"
+      end
+
+      expect(deps).to eq([bar, baz, qux])
+    end
+
+    it "preserves dependency order" do
+      allow(foo).to receive(:to_formula).and_return(double(name: "f", deps: [qux, baz]))
+      expect(described_class.expand(formula)).to eq([qux, baz, foo, bar])
+    end
+  end
+
+  it "skips optionals by default" do
+    deps = [build_dep(:foo, [:optional]), bar, baz, qux]
+    f = double(deps: deps, build: double(with?: false), name: "f")
+    expect(described_class.expand(f)).to eq([bar, baz, qux])
+  end
+
+  it "keeps recommended dependencies by default" do
+    deps = [build_dep(:foo, [:recommended]), bar, baz, qux]
+    f = double(deps: deps, build: double(with?: true), name: "f")
+    expect(described_class.expand(f)).to eq(deps)
+  end
+
+  it "merges repeated dependencies with differing options" do
+    foo2 = build_dep(:foo, ["option"])
+    baz2 = build_dep(:baz, ["option"])
+    deps << foo2 << baz2
+    deps = [foo2, bar, baz2, qux]
+    deps.zip(described_class.expand(formula)) do |expected, actual|
+      expect(expected.tags).to eq(actual.tags)
+      expect(expected).to eq(actual)
+    end
+  end
+
+  it "merges dependencies and perserves env_proc" do
+    env_proc = double
+    dep = described_class.new("foo", [], env_proc)
+    allow(dep).to receive(:to_formula).and_return(double(deps: [], name: "foo"))
+    deps.replace([dep])
+    expect(described_class.expand(formula).first.env_proc).to eq(env_proc)
+  end
+
+  it "merges tags without duplicating them" do
+    foo2 = build_dep(:foo, ["option"])
+    foo3 = build_dep(:foo, ["option"])
+    deps << foo2 << foo3
+
+    expect(described_class.expand(formula).first.tags).to eq(%w[option])
+  end
+
+  it "skips parent but yields children with ::skip" do
+    f = double(
+      name: "f",
+      deps: [
+        build_dep(:foo, [], [bar, baz]),
+        build_dep(:foo, [], [baz]),
+      ],
+    )
+
+    deps = described_class.expand(f) do |_dependent, dep|
+      described_class.skip if %w[foo qux].include? dep.name
+    end
+
+    expect(deps).to eq([bar, baz])
+  end
+
+  it "keeps dependency but prunes recursive dependencies with ::keep_but_prune_recursive_deps" do
+    foo = build_dep(:foo, [:build], bar)
+    baz = build_dep(:baz, [:build])
+    f = double(name: "f", deps: [foo, baz])
+
+    deps = described_class.expand(f) do |_dependent, dep|
+      described_class.keep_but_prune_recursive_deps if dep.build?
+    end
+
+    expect(deps).to eq([foo, baz])
+  end
+
+  it "returns only the dependencies given as a collection as second argument" do
+    expect(formula.deps).to eq([foo, bar, baz, qux])
+    expect(described_class.expand(formula, [bar, baz])).to eq([bar, baz])
+  end
+
+  it "doesn't raise an error when a dependency is cyclic" do
+    foo = build_dep(:foo)
+    bar = build_dep(:bar, [], [foo])
+    allow(foo).to receive(:to_formula).and_return(double(deps: [bar], name: foo.name))
+    f = double(name: "f", deps: [foo, bar])
+    expect { described_class.expand(f) }.not_to raise_error
+  end
+
+  it "cleans the expand stack" do
+    foo = build_dep(:foo)
+    allow(foo).to receive(:to_formula).and_raise(FormulaUnavailableError, foo.name)
+    f = double(name: "f", deps: [foo])
+    expect { described_class.expand(f) }.to raise_error(FormulaUnavailableError)
+    expect(described_class.instance_variable_get(:@expand_stack)).to be_empty
+  end
+end