(FACT-3133) check for command alias in powershell

Powershell aliases certain commands that were not detected by the
`which` facter function; for example, `echo` is aliased to
`Write-Output`. Previously, facter's custom fact resolver would
erroneously report that `echo` did not exist in the subshell
for a Windows custom fact. With this patch, custom facts for
Windows will check if the command is aliased before trying to
resolve it via the path.

Author: tvpartytonight

lib/facter/custom_facts/core/execution/windows.rb

@@ -8,7 +8,14 @@ def search_paths
 
         DEFAULT_COMMAND_EXTENSIONS = %w[.COM .EXE .BAT .CMD].freeze
 
+        def aliased_command?(command)
+          _output, status = Open3.capture2("powershell.exe Get-Alias #{command}")
+          status.success?
+        end
+
         def which(bin)
+          return bin if aliased_command?(bin)
+
           if absolute_path?(bin)
             return bin if File.executable?(bin)
           else

spec/custom_facts/core/execution/windows_spec.rb

@@ -36,6 +36,14 @@
       allow(ENV).to receive(:[]).with('PATHEXT').and_return nil
     end
 
+    context 'when using a command aliased to a Powershell command' do
+      it 'checks for the alias and returns the original queried command' do
+        allow(executor).to receive(:aliased_command?).with('foo.exe').and_return true
+
+        expect(executor.which('foo.exe')).to eq 'foo.exe'
+      end
+    end
+
     context 'when it is provided with an absolute path' do
       it 'returns the path to binary if executable' do
         allow(File).to receive(:executable?).with('C:\Tools\foo.exe').and_return true
@@ -66,13 +74,15 @@
       it 'returns the absolute path if found' do
         allow(File).to receive(:executable?).with('C:\Windows\system32\foo.exe').and_return false
         allow(File).to receive(:executable?).with('C:\Windows\foo.exe').and_return true
+        allow(executor).to receive(:aliased_command?).with('foo.exe').and_return false
 
         expect(executor.which('foo.exe')).to eq 'C:\Windows\foo.exe'
       end
 
       it "won't check all paths if one is executable" do
         allow(File).to receive(:executable?).with('C:\Windows\system32\foo.exe').and_return false
         allow(File).to receive(:executable?).with('C:\Windows\foo.exe').and_return true
+        allow(executor).to receive(:aliased_command?).with('foo.exe').and_return false
 
         expect(File).not_to receive(:executable?).with('C:\Windows\System32\Wbem\foo.exe')
         executor.which('foo.exe')
@@ -87,6 +97,7 @@
           allow(File).to receive(:executable?).with('C:\Windows\foo' + ext).and_return false
         end
         allow(File).to receive(:executable?).with('C:\Windows\foo.EXE').and_return true
+        allow(executor).to receive(:aliased_command?).with('foo').and_return false
 
         expect(executor.which('foo')).to eq 'C:\Windows\foo.EXE'
       end
@@ -95,6 +106,7 @@
         allow(File).to receive(:executable?).with('C:\Windows\system32\foo.exe').and_return false
         allow(File).to receive(:executable?).with('C:\Windows\foo.exe').and_return false
         allow(File).to receive(:executable?).with('C:\Windows\System32\Wbem\foo.exe').and_return false
+        allow(executor).to receive(:aliased_command?).with('foo.exe').and_return false
 
         expect(executor.which('foo.exe')).to be nil
       end