Ensure UUID of command is shared when redacted

In logging, the command UUID displayed in the "command start" phase
was sometimes different to that displayed with the output of the
command. This is because the backend can call `.with_redaction` on a
command when logging the start, and this causes the command to be
duplicated. However, if the `uuid` method hadn't been called before
that point, the copy command would generate its own UUID, distinct
from the original command.

This change avoids that by eagerly calculating the UUID when the
command is created, so that any copied objects share the same UUID.

Author: lazyatom

CHANGELOG.md

@@ -6,6 +6,7 @@ appear at the top.
 ## [Unreleased][]
 
   * Your contribution here!
+* [#455](https://github.com/capistrano/sshkit/pull/455): Ensure UUID of commands are stable in logging - [@lazyatom](https://github.com/lazyatom)
 
 ## [1.18.2][] (2019-02-03)
 

lib/sshkit/command.rb

@@ -9,7 +9,7 @@ class Command
 
     Failed = Class.new(SSHKit::StandardError)
 
-    attr_reader :command, :args, :options, :started_at, :started, :exit_status, :full_stdout, :full_stderr
+    attr_reader :command, :args, :options, :started_at, :started, :exit_status, :full_stdout, :full_stderr, :uuid
 
     # Initialize a new Command object
     #
@@ -25,6 +25,7 @@ def initialize(*args)
       @args    = args
       @options.symbolize_keys!
       @stdout, @stderr, @full_stdout, @full_stderr = String.new, String.new, String.new, String.new
+      @uuid = Digest::SHA1.hexdigest(SecureRandom.random_bytes(10))[0..7]
     end
 
     def complete?
@@ -41,10 +42,6 @@ def started=(new_started)
       @started = new_started
     end
 
-    def uuid
-      @uuid ||= Digest::SHA1.hexdigest(SecureRandom.random_bytes(10))[0..7]
-    end
-
     def success?
       exit_status.nil? ? false : exit_status.to_i == 0
     end

test/unit/test_command.rb

@@ -245,5 +245,10 @@ def test_command_raises_command_failed_error_when_non_zero_exit
       assert_equal "whoami exit status: 1\nwhoami stdout: Nothing written\nwhoami stderr: Nothing written\n", error.message
     end
 
+    def test_shares_same_uuid_before_and_after_redaction
+      command = Command.new(:whoami)
+      command_with_redaction = command.with_redaction
+      assert_equal command.uuid, command_with_redaction.uuid, "UUID should be stable before and after redaction"
+    end
   end
 end