Fallback to Vagrantfile configuration when local metadata lookup fails

The project local metadata file may contain invalid information to properly
lookup the configured box. This may occur if the file has been moved,
modified, or the backing box has been removed. In those cases, fall back
to the configuration defined in the Vagrantfile to load the box.

lib/vagrant/vagrantfile.rb

@@ -170,8 +170,8 @@ module Vagrant
 
       # Track the original box so we know if we changed
       box = nil
-      original_box = config.vm.box
-      original_version = config.vm.box_version
+      initial_box = original_box = config.vm.box
+      initial_version = original_version = config.vm.box_version
 
       # Check if this machine has a local box metadata file
       # describing the existing guest. If so, load it and
@@ -232,6 +232,17 @@ module Vagrant
       # Load the box and provider overrides
       load_box_proc.call
 
+      # NOTE: In cases where the box_meta file contains stale information
+      #       and the reference box no longer exists, fall back to initial
+      #       configuration and attempt to load that
+      if box.nil?
+        @logger.warn("Failed to locate #{config.vm.box} with version #{config.vm.box_version}")
+        @logger.warn("Performing lookup with inital values #{initial_box} with version #{initial_version}")
+        config.vm.box = original_box = initial_box
+        config.vm.box_version = original_box = initial_version
+        load_box_proc.call
+      end
+
       # Ensure box attributes are set to original values in
       # case they were modified by the local box metadata
       config.vm.box = original_box

test/unit/vagrant/vagrantfile_test.rb

@@ -367,6 +367,58 @@ describe Vagrant::Vagrantfile do
       expect { subject.machine_config(:default, :foo, boxes) }.
         to raise_error(Vagrant::Errors::ProviderNotUsable)
     end
+
+    context "local box metadata file" do
+      let(:data_path) { double(:data_path) }
+      let(:meta_file) { double(:meta_file) }
+      let(:box_version) { "2.0" }
+
+      before do
+        register_provider("foo")
+        iso_env.box3("base", "1.0", :foo)
+        allow(data_path).to receive(:join).with("box_meta").
+          and_return(meta_file)
+        allow(meta_file).to receive(:file?).and_return(false)
+        configure do |config|
+          config.vm.box = "base"
+          config.vm.box_version = box_version
+        end
+      end
+
+      it "checks for local box metadata file" do
+        expect(meta_file).to receive(:file?).and_return(false)
+        subject.machine_config(:default, :foo, boxes, data_path)
+      end
+
+      context "file exists" do
+        let(:meta_file_content) { '{"name":"base","version":"1.0"}' }
+
+        before do
+          allow(meta_file).to receive(:file?).and_return(true)
+          allow(meta_file).to receive(:read).and_return(meta_file_content)
+        end
+
+        it "reads the local box metadata file" do
+          expect(meta_file).to receive(:read).and_return(meta_file_content)
+          subject.machine_config(:default, :foo, boxes, data_path)
+        end
+
+        it "properly loads the box defined in metadata" do
+          result = subject.machine_config(:default, :foo, boxes, data_path)
+          expect(result[:box]).not_to be_nil
+        end
+
+        context "with invalid box version" do
+          let(:box_version) { "1.0" }
+          let(:meta_file_content) { '{"name":"base","version":"2.0"}' }
+
+          it "loads box base on Vagrantfile information" do
+            result = subject.machine_config(:default, :foo, boxes, data_path)
+            expect(result[:box]).not_to be_nil
+          end
+        end
+      end
+    end
   end
 
   describe "#machine_names" do