Check for vagrant.exe path before validating versions

lib/vagrant/util/platform.rb

@@ -447,18 +447,20 @@ module Vagrant
         # are the same. Raise error if they do not match.
         def wsl_validate_matching_vagrant_versions!
           valid = false
-          result = Util::Subprocess.execute("vagrant.exe", "version")
-          if result.exit_code == 0
-            windows_version = result.stdout.match(/Installed Version: (?<version>[\w.-]+)/)
-            if windows_version
-              windows_version = windows_version[:version].strip
-              valid = windows_version == Vagrant::VERSION
+          if Util::Which.which("vagrant.exe")
+            result = Util::Subprocess.execute("vagrant.exe", "version")
+            if result.exit_code == 0
+              windows_version = result.stdout.match(/Installed Version: (?<version>[\w.-]+)/)
+              if windows_version
+                windows_version = windows_version[:version].strip
+                valid = windows_version == Vagrant::VERSION
+              end
+            end
+            if !valid
+              raise Vagrant::Errors::WSLVagrantVersionMismatch,
+                wsl_version: Vagrant::VERSION,
+                windows_version: windows_version || "unknown"
             end
-          end
-          if !valid
-            raise Vagrant::Errors::WSLVagrantVersionMismatch,
-              wsl_version: Vagrant::VERSION,
-              windows_version: windows_version || "unknown"
           end
         end
 

test/unit/vagrant/util/platform_test.rb

@@ -182,4 +182,36 @@ describe Vagrant::Util::Platform do
       expect(subject.systemd?).to be_falsey
     end
   end
+
+  describe ".wsl_validate_matching_vagrant_versions!" do
+    let(:exe_version){ Vagrant::VERSION.to_s }
+
+    before do
+      allow(Vagrant::Util::Which).to receive(:which).and_return(true)
+      allow(Vagrant::Util::Subprocess).to receive(:execute).with("vagrant.exe", "version").
+        and_return(double(exit_code: 0, stdout: "Installed Version: #{exe_version}"))
+    end
+
+    it "should not raise an error" do
+      Vagrant::Util::Platform.wsl_validate_matching_vagrant_versions!
+    end
+
+    context "when windows vagrant.exe is not installed" do
+      before{ expect(Vagrant::Util::Which).to receive(:which).with("vagrant.exe").and_return(nil) }
+
+      it "should not raise an error" do
+        Vagrant::Util::Platform.wsl_validate_matching_vagrant_versions!
+      end
+    end
+
+    context "when versions do not match" do
+      let(:exe_version){ "1.9.9" }
+
+      it "should raise an error" do
+        expect {
+          Vagrant::Util::Platform.wsl_validate_matching_vagrant_versions!
+        }.to raise_error(Vagrant::Errors::WSLVagrantVersionMismatch)
+      end
+    end
+  end
 end