Fix LANG value used for VirtualBox driver

The VirtualBox driver sets the LANG env var to prevent localized output
being returned when executing CLI commands. If the `locale` command is
present, do a best effort lookup to determine the properly value to use
for the LANG environment variable.

plugins/providers/virtualbox/driver/base.rb

@@ -462,7 +462,7 @@ module VagrantPlugins
           # Append in the options for subprocess
           # NOTE: We include the LANG env var set to C to prevent command output
           #       from being localized
-          command << { notify: [:stdout, :stderr], env: {LANG: "C"}}
+          command << { notify: [:stdout, :stderr], env: env_lang}
 
           Vagrant::Util::Busy.busy(int_callback) do
             Vagrant::Util::Subprocess.execute(@vboxmanage_path, *command, &block)
@@ -471,6 +471,52 @@ module VagrantPlugins
           raise Vagrant::Errors::VBoxManageLaunchError,
             message: e.to_s
         end
+
+        private
+
+        # List of LANG values to attempt to use
+        LANG_VARIATIONS = %w(C C.UTF-8 C.utf8 en_US.UTF-8 en_US.utf8 POSIX).map(&:freeze).freeze
+
+        # By default set the LANG to C. If the host has the locale command
+        # available, check installed locales and verify C is included (or
+        # use C variant if available).
+        def env_lang
+          # If already set, just return immediately
+          return @env_lang if @env_lang
+
+          # Default the LANG to C
+          @env_lang = {LANG: "C"}
+
+          # If the locale command is not available, return default
+          return @env_lang if !Vagrant::Util::Which.which("locale")
+
+          @logger.debug("validating LANG value for virtualbox cli commands")
+          # Get list of available locales on the system
+          result = Vagrant::Util::Subprocess.execute("locale", "-a")
+
+          # If the command results in an error, just log the error
+          # and return the default value
+          if result.exit_code != 0
+            @logger.warn("locale command failed (exit code: #{result.exit_code}): #{result.stderr}")
+            return @env_lang
+          end
+          available = result.stdout.lines.map(&:chomp).find_all { |l|
+            l == "C" || l == "POSIX" || l.start_with?("C.") || l.start_with?("en_US.")
+          }
+          @logger.debug("list of available C locales: #{available.inspect}")
+
+          # Attempt to find a valid LANG from locale list
+          lang = LANG_VARIATIONS.detect { |l| available.include?(l) }
+
+          if lang
+            @logger.debug("valid variation found for LANG value: #{lang}")
+            @env_lang[:LANG] = lang
+          end
+
+          @logger.debug("LANG value set: #{@env_lang[:LANG].inspect}")
+
+          @env_lang
+        end
       end
     end
   end

test/unit/plugins/providers/virtualbox/driver/base.rb

@@ -0,0 +1,99 @@
+require_relative "../base"
+require Vagrant.source_root.join("plugins/providers/virtualbox/driver/base")
+
+describe VagrantPlugins::ProviderVirtualBox::Driver::Base do
+  describe "#env_lang" do
+    context "when locale command is not available" do
+      before do
+        allow(Vagrant::Util::Which).to receive(:which).with("locale").and_return(false)
+      end
+
+      it "should return default value" do
+        expect(subject.send(:env_lang)).to eq({LANG: "C"})
+      end
+    end
+
+    context "when the locale command is available" do
+      let(:result) { Vagrant::Util::Subprocess::Result.new(exit_code, stdout, stderr) }
+      let(:stderr) { "" }
+      let(:stdout) { "C.default" }
+      let(:exit_code) { 0 }
+
+      before do
+        allow(Vagrant::Util::Which).to receive(:which).with("locale").and_return(true)
+        allow(Vagrant::Util::Subprocess).to receive(:execute).with("locale", "-a").and_return(result)
+      end
+
+      context "when locale command errors" do
+        let(:exit_code) { 1 }
+
+        it "should return default value" do
+          expect(subject.send(:env_lang)).to eq({LANG: "C"})
+        end
+      end
+
+      context "when locale command does not error" do
+        let(:exit_code) { 0 }
+        let(:base) { "de_AT.utf8\nde_BE.utf8\nde_CH.utf8\nde_DE.utf8\nde_IT.utf8\nde_LI.utf8\nde_LU.utf8\nen_AG\nen_AG.utf8\nen_AU.utf8\nen_BW.utf8\nen_CA.utf8\nen_DK.utf8\nen_GB.utf8\nen_HK.utf8\nen_IE.utf8\nen_IL\nen_IL.utf8\nen_IN\nen_IN.utf8\nen_NG\n" }
+
+        context "when stdout includes C" do
+          let(:stdout) { "#{base}C\n" }
+
+          it "should use C for the lang" do
+            expect(subject.send(:env_lang)).to eq({LANG: "C"})
+          end
+        end
+
+        context "when stdout does not include C" do
+          context "when stdout includes C.UTF-8" do
+            let(:stdout) { "#{base}C.UTF-8\n"}
+
+            it "should use C.UTF-8 for the lang" do
+              expect(subject.send(:env_lang)).to eq({LANG: "C.UTF-8"})
+            end
+          end
+
+          context "when stdout includes C.utf8" do
+            let(:stdout) { "#{base}C.utf8\n"}
+
+            it "should use C.utf8 for the lang" do
+              expect(subject.send(:env_lang)).to eq({LANG: "C.utf8"})
+            end
+          end
+
+          context "when stdout includes POSIX" do
+            let(:stdout) { "#{base}POSIX\n"}
+
+            it "should use POSIX for the lang" do
+              expect(subject.send(:env_lang)).to eq({LANG: "POSIX"})
+            end
+          end
+
+          context "when stdout includes en_US.UTF-8" do
+            let(:stdout) { "#{base}en_US.UTF-8\n"}
+
+            it "should use en_US.UTF-8 for the lang" do
+              expect(subject.send(:env_lang)).to eq({LANG: "en_US.UTF-8"})
+            end
+          end
+
+          context "when stdout includes en_US.utf8" do
+            let(:stdout) { "#{base}en_US.utf8\n"}
+
+            it "should use en_US.utf8 for the lang" do
+              expect(subject.send(:env_lang)).to eq({LANG: "en_US.utf8"})
+            end
+          end
+        end
+
+        context "when stdout does not include any variations" do
+          let(:stdout) { base }
+
+          it "should default to C" do
+            expect(subject.send(:env_lang)).to eq({LANG: "C"})
+          end
+        end
+      end
+    end
+  end
+end

test/unit/support/shared/virtualbox_context.rb

@@ -28,6 +28,9 @@ shared_context "virtualbox" do
     allow(subprocess).to receive(:execute).
       with("VBoxManage", "showvminfo", kind_of(String), kind_of(Hash)).
       and_return(subprocess_result(exit_code: 0))
+
+    allow(Vagrant::Util::Which).to receive(:which).and_call_original
+    allow(Vagrant::Util::Which).to receive(:which).with("locale").and_return(false)
   end
 
   around do |example|