[EnvironmentCookbookVersionsEndpoint] Test #depsolve

Add comprehensive unit tests for the depsolve dependency solver:
- empty versions returns nil and sets @last_constraint_failure
- empty unsolved list returns desired_versions unchanged
- single cookbook with no dependencies resolves to latest
- cookbook with satisfiable dependency resolves both
- missing dependency cookbook returns nil and sets @last_missing_dep
- backtracking to older version when newest has unsatisfiable dep
- environment constraints applied to dependency versions
- dependency's own version constraint filters available versions
- pre-tracked dependency not narrowed to single version (known failure)
- unsatisfiable dep constraint (all versions filtered) returns nil
- cache accumulates entries for all resolved cookbooks
- multiple independent unsolved cookbooks resolve to latest
- diamond dependency (two cookbooks sharing a dep)
- conflicting dependency constraints returns nil
- deep dependency chain (A -> B -> C)
- multiple backtracking steps (v3, v2 fail, v1 succeeds)
- cookbook with missing metadata key uses fallback

Signed-off-by: David Crosby <dcrosby@fb.com>

Author: dafyddcrosby

spec/endpoints/environment_cookbook_versions_endpoint_spec.rb

@@ -1,3 +1,4 @@
+require "uri" unless defined?(URI)
 require "chef_zero/endpoints/environment_cookbook_versions_endpoint"
 
 describe ChefZero::Endpoints::EnvironmentCookbookVersionsEndpoint do
@@ -58,4 +59,342 @@
       expect(versions).to eq(original)
     end
   end
+
+  describe "#depsolve" do
+    let(:org_prefix) { %w{organizations testorg} }
+    let(:request) { double("request", rest_path: org_prefix + %w{environments _default cookbook_versions}) }
+    let(:data_store) { double("data_store") }
+
+    before do
+      allow(server).to receive(:data_store).and_return(data_store)
+    end
+
+    def cookbook_json(name, version, dependencies = {})
+      FFI_Yajl::Encoder.encode({
+        "metadata" => {
+          "name" => name,
+          "version" => version,
+          "dependencies" => dependencies,
+        },
+      })
+    end
+
+    context "base cases" do
+      it "returns [nil, nil] when a cookbook has empty versions" do
+        desired = { "apache" => [] }
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result).to be_nil
+      end
+
+      it "sets @last_constraint_failure when a cookbook has empty versions" do
+        desired = { "apache" => [] }
+        endpoint.depsolve(request, ["apache"], desired, {})
+        expect(endpoint.instance_variable_get(:@last_constraint_failure)).to eq("apache")
+      end
+
+      it "returns desired_versions when unsolved list is empty" do
+        desired = { "apache" => ["1.0.0"] }
+        result, _cache = endpoint.depsolve(request, [], desired, {})
+        expect(result).to eq(desired)
+      end
+
+      it "resolves a cookbook with no metadata key" do
+        desired = { "minimal" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "minimal", "1.0.0"], request)
+          .and_return(FFI_Yajl::Encoder.encode({}))
+
+        result, cache = endpoint.depsolve(request, ["minimal"], desired, {})
+        expect(result["minimal"]).to eq(["1.0.0"])
+        expect(cache["minimal"]).to have_key("1.0.0")
+      end
+    end
+
+    context "simple resolution" do
+      it "resolves a single cookbook with no dependencies" do
+        desired = { "apache" => ["1.0.0", "2.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "2.0.0"], request)
+          .and_return(cookbook_json("apache", "2.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0"))
+
+        result, cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result["apache"]).to eq(["2.0.0"])
+        expect(cache["apache"]["2.0.0"]).to be_a(Hash)
+      end
+
+      it "resolves a cookbook with a satisfiable dependency" do
+        desired = { "apache" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 1.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "2.0.0"], request)
+          .and_return(cookbook_json("mysql", "2.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "1.0.0"], request)
+          .and_return(cookbook_json("mysql", "1.0.0"))
+
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result["apache"]).to eq(["1.0.0"])
+        expect(result["mysql"]).to eq(["2.0.0"])
+      end
+
+      it "returns [nil, nil] when a dependency cookbook does not exist" do
+        desired = { "apache" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "missing" => ">= 0.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks missing})
+          .and_return(false)
+
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result).to be_nil
+        expect(endpoint.instance_variable_get(:@last_missing_dep)).to eq("missing")
+      end
+    end
+
+    context "constraint filtering" do
+      it "applies environment constraints to dependency versions" do
+        desired = { "apache" => ["1.0.0"] }
+        env_constraints = { "mysql" => "= 1.0.0" }
+
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 0.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "1.0.0"], request)
+          .and_return(cookbook_json("mysql", "1.0.0"))
+
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, env_constraints)
+        expect(result["mysql"]).to eq(["1.0.0"])
+      end
+
+      it "filters dependency versions by the dependency's own constraint" do
+        desired = { "apache" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 2.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "2.0.0"], request)
+          .and_return(cookbook_json("mysql", "2.0.0"))
+
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result["mysql"]).to eq(["2.0.0"])
+      end
+
+      it "returns nil when dep constraint filters out all available versions" do
+        desired = { "apache" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 5.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0"])
+
+        result, _cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(result).to be_nil
+      end
+    end
+
+    context "backtracking" do
+      it "falls back to an older version when newest has unsatisfiable dep" do
+        desired = { "web" => ["1.0.0", "2.0.0"] }
+        # v2.0.0 depends on "ghost" which doesn't exist
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "web", "2.0.0"], request)
+          .and_return(cookbook_json("web", "2.0.0", { "ghost" => ">= 0.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks ghost})
+          .and_return(false)
+        # v1.0.0 has no deps
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "web", "1.0.0"], request)
+          .and_return(cookbook_json("web", "1.0.0"))
+
+        result, _cache = endpoint.depsolve(request, ["web"], desired, {})
+        expect(result["web"]).to eq(["1.0.0"])
+      end
+
+      it "backtracks through multiple failing versions" do
+        desired = { "web" => ["1.0.0", "2.0.0", "3.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "web", "3.0.0"], request)
+          .and_return(cookbook_json("web", "3.0.0", { "missing_a" => ">= 0.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks missing_a})
+          .and_return(false)
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "web", "2.0.0"], request)
+          .and_return(cookbook_json("web", "2.0.0", { "missing_b" => ">= 0.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks missing_b})
+          .and_return(false)
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "web", "1.0.0"], request)
+          .and_return(cookbook_json("web", "1.0.0"))
+
+        result, _cache = endpoint.depsolve(request, ["web"], desired, {})
+        expect(result["web"]).to eq(["1.0.0"])
+      end
+    end
+
+    context "multiple cookbooks and dependencies" do
+      it "populates cache entries for all resolved cookbooks" do
+        desired = { "apache" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 1.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "1.0.0"], request)
+          .and_return(cookbook_json("mysql", "1.0.0"))
+
+        _result, cache = endpoint.depsolve(request, ["apache"], desired, {})
+        expect(cache["apache"]).to have_key("1.0.0")
+        expect(cache["apache"]["1.0.0"]["metadata"]["name"]).to eq("apache")
+        expect(cache["mysql"]).to have_key("1.0.0")
+        expect(cache["mysql"]["1.0.0"]["metadata"]["name"]).to eq("mysql")
+      end
+
+      it "resolves multiple independent unsolved cookbooks" do
+        desired = {
+          "apache" => ["1.0.0", "2.0.0"],
+          "nginx" => ["3.0.0", "4.0.0"],
+        }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "2.0.0"], request)
+          .and_return(cookbook_json("apache", "2.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "nginx", "4.0.0"], request)
+          .and_return(cookbook_json("nginx", "4.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "nginx", "3.0.0"], request)
+          .and_return(cookbook_json("nginx", "3.0.0"))
+
+        result, cache = endpoint.depsolve(request, %w{apache nginx}, desired, {})
+        expect(result["apache"]).to eq(["2.0.0"])
+        expect(result["nginx"]).to eq(["4.0.0"])
+        expect(cache.keys).to contain_exactly("apache", "nginx")
+      end
+
+      it "resolves a diamond dependency (two cookbooks sharing a dep)" do
+        desired = {
+          "apache" => ["1.0.0"],
+          "nginx" => ["1.0.0"],
+        }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 1.0.0" }))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "nginx", "1.0.0"], request)
+          .and_return(cookbook_json("nginx", "1.0.0", { "mysql" => ">= 2.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0", "3.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "3.0.0"], request)
+          .and_return(cookbook_json("mysql", "3.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "mysql", "2.0.0"], request)
+          .and_return(cookbook_json("mysql", "2.0.0"))
+
+        result, _cache = endpoint.depsolve(request, %w{apache nginx}, desired, {})
+        expect(result["apache"]).to eq(["1.0.0"])
+        expect(result["nginx"]).to eq(["1.0.0"])
+        expect(result["mysql"]).to eq(["3.0.0"])
+      end
+
+      it "returns nil when dependency constraints from two cookbooks conflict" do
+        desired = {
+          "apache" => ["1.0.0"],
+          "nginx" => ["1.0.0"],
+        }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "apache", "1.0.0"], request)
+          .and_return(cookbook_json("apache", "1.0.0", { "mysql" => ">= 2.0.0" }))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "nginx", "1.0.0"], request)
+          .and_return(cookbook_json("nginx", "1.0.0", { "mysql" => "< 2.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks mysql})
+          .and_return(["1.0.0", "2.0.0"])
+
+        result, _cache = endpoint.depsolve(request, %w{apache nginx}, desired, {})
+        expect(result).to be_nil
+      end
+
+      it "resolves a deep dependency chain" do
+        desired = { "app" => ["1.0.0"] }
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "app", "1.0.0"], request)
+          .and_return(cookbook_json("app", "1.0.0", { "framework" => ">= 1.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks framework})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks framework})
+          .and_return(["1.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "framework", "1.0.0"], request)
+          .and_return(cookbook_json("framework", "1.0.0", { "lib" => ">= 1.0.0" }))
+        allow(data_store).to receive(:exists_dir?)
+          .with(org_prefix + %w{cookbooks lib})
+          .and_return(true)
+        allow(data_store).to receive(:list)
+          .with(org_prefix + %w{cookbooks lib})
+          .and_return(["1.0.0", "2.0.0"])
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "lib", "2.0.0"], request)
+          .and_return(cookbook_json("lib", "2.0.0"))
+        allow(data_store).to receive(:get)
+          .with(org_prefix + ["cookbooks", "lib", "1.0.0"], request)
+          .and_return(cookbook_json("lib", "1.0.0"))
+
+        result, cache = endpoint.depsolve(request, ["app"], desired, {})
+        expect(result["app"]).to eq(["1.0.0"])
+        expect(result["framework"]).to eq(["1.0.0"])
+        expect(result["lib"]).to eq(["2.0.0"])
+        expect(cache.keys).to contain_exactly("app", "framework", "lib")
+      end
+    end
+  end
 end