(maint) Stop invalid debug logs from crashing services

Previously if an invalid logfile location was specified e.g. C:\ or a missing
parent directory, the service (Language or Debug Server) would error.  This is
undesired as a bad log file should not cause a catastrophic failure.  This
commit modifies the logging so that an error occurs when the log file is
created it, the error is sent to STDERR, and service continues but with logging
disabled.

This commit also flushes the log file on each write if needed.  This is required
as OS buffering makes real time debugging very difficult.

CHANGELOG.md

@@ -8,6 +8,7 @@ Check [Keep a Changelog](http://keepachangelog.com/) for recommendations on how
 
 - ([GH-11](https://github.com/lingua-pupuli/puppet-editor-services/issues/11)) Refactor the transport layers to loosen object coupling
 - ([GH-11](https://github.com/lingua-pupuli/puppet-editor-services/issues/11)) Fix STDIO server
+- Stop bad logfile destinations from crashing the language and debug servers
 
 ## 0.10.0 - 2018-03-29
 

lib/puppet-editor-services/logging.rb

@@ -16,16 +16,28 @@ def self.log_message(severity, message)
     else
       @logger.unknown(message)
     end
+    @log_file.fsync unless @log_file.nil?
   end
 
   def self.init_logging(options)
+    @log_file = nil
     if options[:debug].nil?
       @logger = nil
     elsif (options[:debug].casecmp 'stdout').zero?
       @logger = Logger.new($stdout)
     elsif !options[:debug].to_s.empty?
       # Log to file
-      @logger = Logger.new(options[:debug])
+      begin
+        @log_file = File.open(options[:debug], 'w')
+      rescue Errno::ENOENT => e
+        # We can't open the log file and we can't log to STDOUT if we're in STDIO mode
+        # So log the error to STDERR and disable logging
+        $stderr.puts "Error opening log file #{options[:debug]} : #{e}" # rubocop:disable Style/StderrPuts
+        @log_file = nil
+        return
+      end
+      @log_file.sync = true
+      @logger = Logger.new(@log_file)
     end
   end
 end