move lookup of parent providers for attributes from runner to provides_map

4 files changed, 65 insertions, 74 deletions

diff --git a/lib/ohai/provides_map.rb b/lib/ohai/provides_map.rb
index 2981e071..15fa939a 100644
--- a/lib/ohai/provides_map.rb
+++ b/lib/ohai/provides_map.rb
@@ -51,14 +51,26 @@ module Ohai
       end
     end
 
-    def find_providers_for(attributes)
+    # inherit = false => only look up providers for a listed
+    # attribute, don't look for parent providers
+    # inherit = true => looks up parent attribute providers if no
+    # providers for a listed attribute are found first
+    def find_providers_for(attributes, inherit = false)
       plugins = []
       attributes.each do |attribute|
         attrs = map
         parts = attribute.split('/')
         parts.each do |part|
+          # TODO: pretty sure we can remove this line, below
           next if part == Ohai::Mixin::OS.collect_os
-          raise Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute \'#{attribute}\'" unless attrs[part]
+          unless attrs[part]
+            # this attribute does not exist in the map.
+            # raise an error if inherit == false (we aren't looking up
+            # parent providers) or attrs[parts[0]] doesn't exist (in
+            # that case, no parents to look for)
+            raise Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute \'#{attribute}\'" unless inherit && attrs != map
+            break # otherwise (inherit == true and we have the deepest parent of this attribute)
+          end
           attrs = attrs[part]
         end
         plugins += collect_plugins_in(attrs, [])
@@ -66,7 +78,6 @@ module Ohai
       plugins.uniq
     end
 
-
     def all_plugins(attribute_filter=nil)
       if attribute_filter.nil?
         collected = []
diff --git a/lib/ohai/runner.rb b/lib/ohai/runner.rb
index f1726c02..8c7eca1a 100644
--- a/lib/ohai/runner.rb
+++ b/lib/ohai/runner.rb
@@ -85,45 +85,8 @@ module Ohai
       end
     end
 
-    # returns a list of plugins which provide the given attributes
     def fetch_plugins(attributes)
-      plugins = []
-      # subattribute_regex matches the lowest subattribute of any
-      # given attribute. if the attribute is 'attr/sub1/sub2', then
-      # subattribute_regex matches '/sub2'. if the attribute is 'attr'
-      # then subattribute_regex matches nothing.
-      subattribute_regex = Regexp.new("/[^/]+$")
-      attributes.each do |attribute|
-        partial_attribute = attribute
-        # look for providers until 1) we find some, or 2) we've
-        # exhaused our search (the highest-level of the attribute
-        # doesn't return any results
-        while (found_providers = safe_find_providers_for(partial_attribute)).empty?
-          md = subattribute_regex.match(partial_attribute)
-          # since md doesn't match the highest-level attribute, if md
-          # is nil, then we can't look any higher. this attribute
-          # really does not exist.
-          raise Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing #{attribute}" unless md
-          # remove the lowest-level subattribute and look again
-          # don't use chomp! affects attribute, too.
-          partial_attribute = partial_attribute.chomp(md[0])
-        end
-        plugins << found_providers
-        plugins.flatten!
-      end
-      plugins.uniq
-    end
-
-    # "safely" finds providers for a single attribute. by "safe", if
-    # there are no plugins providing the attribute, return an empty
-    # array to indicate this (don't raise
-    # Ohai::Exceptions::AttributeNotFound error)
-    def safe_find_providers_for(attribute)
-      begin
-        @provides_map.find_providers_for([attribute])
-      rescue Ohai::Exceptions::AttributeNotFound
-        return []
-      end
+      @provides_map.find_providers_for(attributes, true)
     end
 
     # Given a list of plugins and the first plugin in the cycle,
diff --git a/spec/unit/provides_map_spec.rb b/spec/unit/provides_map_spec.rb
index 26552772..fbc026fe 100644
--- a/spec/unit/provides_map_spec.rb
+++ b/spec/unit/provides_map_spec.rb
@@ -29,6 +29,16 @@ describe Ohai::ProvidesMap do
   let(:plugin_4) { Ohai::DSL::Plugin.new(ohai_system.data) }
 
   describe "when looking up providing plugins for a single attribute" do
+    describe "when no plugin provides the attribute" do
+      it "should raise Ohai::Exceptions::AttributeNotFound error, with inherit = false" do
+        expect{ provides_map.find_providers_for(["single"]) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute 'single'")
+      end
+
+      it "should raise Ohai::Exceptions::AttributeNotFound error, with inherit = true" do
+        expect{ provides_map.find_providers_for(["single"], true) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute 'single'")
+      end
+    end
+
     describe "when only one plugin provides the attribute" do
       before do
         provides_map.set_providers_for(plugin_1, ["single"])
@@ -78,12 +88,45 @@ describe Ohai::ProvidesMap do
   end
 
   describe "when looking up providers for multi-level attributes" do
-    before do
-      provides_map.set_providers_for(plugin_1, ["top/middle/bottom"])
+    describe "when the full attribute exists in the map" do
+      before do
+        provides_map.set_providers_for(plugin_1, ["top/middle/bottom"])
+      end
+
+      it "should collect the provider" do
+        expect(provides_map.find_providers_for(["top/middle/bottom"])).to eq([plugin_1])
+      end
     end
 
-    it "should collect the provider" do
-      expect(provides_map.find_providers_for(["top/middle/bottom"])).to eq([plugin_1])
+    describe "when the full attribute doesn't exist in the map" do
+      context "and inherit = false" do
+        before do
+          provides_map.set_providers_for(plugin_1, ["top/middle"])
+        end
+
+        it "should raise Ohai::Exceptions::AttributeNotFound error" do
+          expect{ provides_map.find_providers_for(["top/middle/bottom"]) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute 'top/middle/bottom'")
+        end
+      end
+
+      context "and inherit = true" do
+        before do
+          provides_map.set_providers_for(plugin_1, ["top"])
+          provides_map.set_providers_for(plugin_2, ["top/middle"])
+        end
+
+        it "should not raise error" do
+          expect{ provides_map.find_providers_for(["top/middle/bottom"], true) }.not_to raise_error
+        end
+
+        it "should return the most specific parent provider" do
+          expect(provides_map.find_providers_for(["top/middle/bottom"], true)).to eq([plugin_2])
+        end
+
+        it "should raise Ohai::Exceptions::AttributeNotFound error if no parent exists" do
+          expect{ provides_map.find_providers_for(["one/two/three"], true) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute 'one/two/three'")
+        end
+      end
     end
 
     it "should collect the provider" do
@@ -100,7 +143,6 @@ describe Ohai::ProvidesMap do
     end
 
     it "should find all the plugins providing attributes" do
-
       all_plugins = provides_map.all_plugins
       expect(all_plugins).to have(4).plugins
       expect(all_plugins).to include(plugin_1)
diff --git a/spec/unit/runner_spec.rb b/spec/unit/runner_spec.rb
index 0fb65283..36c0c0d8 100644
--- a/spec/unit/runner_spec.rb
+++ b/spec/unit/runner_spec.rb
@@ -381,31 +381,6 @@ describe Ohai::Runner, "run_plugin" do
   end
 end
 
-describe Ohai::Runner, "safe_find_providers_for" do
-  before(:each) do
-    @provides_map = Ohai::ProvidesMap.new
-    @data = Mash.new
-    @ohai = double('Ohai::System', :data => @data, :provides_map => @provides_map)
-    @runner = Ohai::Runner.new(@ohai, true)
-  end
-
-  it "should return an empty array if there are no providers for an attribute" do
-    # nothing in the provides map
-    @runner.safe_find_providers_for("false/attribute").should be_empty
-  end
-
-  it "should not raise an error if there are no providers for an attribute" do
-    # nothing in the provides map
-    expect{ @runner.safe_find_providers_for("false/attribute") }.not_to raise_error
-  end
-
-  it "should return the providers for an attribute that exists" do
-    plugin = Ohai::DSL::Plugin.new(@ohai, "tmp/plugins/real.rb")
-    @provides_map.set_providers_for(plugin, ["real/attribute"])
-    @runner.safe_find_providers_for("real/attribute").should eql([plugin]) 
-  end
-end
-
 describe Ohai::Runner, "fetch_plugins" do
   before(:each) do
     @provides_map = Ohai::ProvidesMap.new
@@ -425,7 +400,7 @@ describe Ohai::Runner, "fetch_plugins" do
   describe "when the attribute is not provided by any plugin" do
     describe "and some parent attribute has providers" do
       it "should return the providers for the parent" do
-        plugin = Ohai::DSL::Plugin.new(@ohai, "tmp/plugins/test.rb")
+        plugin = Ohai::DSL::Plugin.new(@ohai.data)
         @provides_map.set_providers_for(plugin, ["test/attribute"])
         @runner.fetch_plugins(["test/attribute/too_far"]).should eql([plugin])
       end
@@ -434,13 +409,13 @@ describe Ohai::Runner, "fetch_plugins" do
     describe "and no parent attribute has providers" do
       it "should raise Ohai::Exceptions::AttributeNotFound exception" do
         # provides map is empty
-        expect{ @runner.fetch_plugins(["false/attribute"]) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing false/attribute")
+        expect{ @runner.fetch_plugins(["false/attribute"]) }.to raise_error(Ohai::Exceptions::AttributeNotFound, "Cannot find plugin providing attribute 'false/attribute'")
       end
     end
   end
 
   it "should return unique providers" do
-    plugin = Ohai::DSL::Plugin.new(@ohai, "tmp/plugins/test.rb")
+    plugin = Ohai::DSL::Plugin.new(@ohai.data)
     @provides_map.set_providers_for(plugin, ["test", "test/too_far/way_too_far"])
     @runner.fetch_plugins(["test", "test/too_far/way_too_far"]).should eql([plugin])
   end