Add fallback to Ruby Digest if command isn't found

Signed-off-by: Jerry Aldrich <[email protected]>

lib/train/file.rb

@@ -178,7 +178,7 @@ def perform_checksum(method)
       res = @backend.run_command(cmd)
       return res.stdout.split(' ').first if res.exit_status == 0
 
-      raise_checksum_error(cmd, res)
+      perform_ruby_checksum(method)
     end
 
     def perform_checksum_windows(method)
@@ -187,13 +187,24 @@ def perform_checksum_windows(method)
       res = @backend.run_command(cmd)
       return res.stdout.split("\r\n")[1].tr(' ', '') if res.exit_status == 0
 
-      raise_checksum_error(cmd, res)
+      perform_ruby_checksum(method)
     end
 
-    def raise_checksum_error(cmd, res)
-      fail "Failed to get checksum with `#{cmd}`.\n" \
-           "STDOUT: #{res.stdout}\n" \
-           "STDERR: #{res.stderr}\n"
+    # This pulls the content of the file to the machine running Train and uses
+    # Digest to perform the checksum. This is less efficient than using remote
+    # system binaries and can lead to incorrect results due to encoding.
+    def perform_ruby_checksum(method)
+      case method
+      when :md5
+        res = Digest::MD5.new
+      when :sha256
+        res = Digest::SHA256.new
+      end
+
+      res.update(content)
+      res.hexdigest
+    rescue TypeError => _
+      nil
     end
   end
 end

test/unit/file/remote/qnx_test.rb

@@ -43,23 +43,28 @@
   end
 
   describe '#md5sum' do
-    it 'raises an error matching /command not found/' do
+    it 'performs a checksum via Ruby if the `md5sum` command fails' do
       stderr = 'md5sum: command not found'
       backend.mock_command('md5sum /tmp/testfile', nil, stderr, 1)
-      proc { cls.new(backend, '/tmp/testfile').md5sum }
-        .must_raise RuntimeError, /md5sum: command not found/
+
+      cls.new(backend, '/tmp/testfile').stub :content, 'mock' do |i|
+        i.md5sum.must_equal '17404a596cbd0d1e6c7d23fcd845ab82'
+      end
     end
   end
 
   describe '#sha256sum' do
     let(:sha256_checksum) {
-      '491260aaa6638d4a64c714a17828c3d82bad6ca600c9149b3b3350e91bcd283d'
+      'ec864fe99b539704b8872ac591067ef22d836a8d942087f2dba274b301ebe6e5'
     }
 
-    it 'calculates the correct sha256sum on the `qnx` platform family' do
-      output = "#{sha256_checksum} /tmp/testfile"
-      backend.mock_command('shasum -a 256 /tmp/testfile', output)
-      cls.new(backend, '/tmp/testfile').sha256sum.must_equal sha256_checksum
+    it 'performs a checksum via Ruby if the `sha256sum` command fails' do
+      stderr = 'sha256sum: command not found'
+      backend.mock_command('sha256sum /tmp/testfile', nil, stderr, 1)
+
+      cls.new(backend, '/tmp/testfile').stub :content, 'mock' do |i|
+        i.sha256sum.must_equal sha256_checksum
+      end
     end
   end
 end

test/unit/file_test.rb

@@ -71,7 +71,6 @@ def mockup(stubs)
     new_cls.file_version.must_be_nil
   end
 
-
   describe 'type' do
     it 'recognized type == file' do
       fc = mockup(type: :file)