Retry fetch specs with `--retry`

This PR adds a general purpose Retry class that can be re-used where-ever retry code is needed!

It also allows you to call `bundle install --retry 3` which will attempt to connect to ruby gems 3 times before failing, and emit a warning message each time

1 files changed, 48 insertions, 0 deletions

diff --git a/lib/bundler/retry.rb b/lib/bundler/retry.rb
new file mode 100644
index 00000000..ff53ff54
--- /dev/null
+++ b/lib/bundler/retry.rb
@@ -0,0 +1,48 @@
+module Bundler
+  # General purpose class for retrying code that may fail
+  class Retry
+    attr_accessor :name, :max_attempts, :current_attempt
+
+    def initialize(name, max_attempts = 1)
+      @name            = name
+      @max_attempts    = max_attempts
+    end
+
+    def attempt(&block)
+      @current_attempt = 0
+      @failed          = false
+      @error           = nil
+      while keep_trying? do
+        run(&block)
+      end
+      @result
+    end
+    alias :attempts :attempt
+
+  private
+    def run(&block)
+      @failed          = false
+      @current_attempt += 1
+      @result = block.call
+    rescue => e
+      fail(e)
+    end
+
+    def fail(e)
+      @failed = true
+      raise e if last_attempt?
+      return true unless name
+      Bundler.ui.warn "Retrying #{name} due to error (#{current_attempt.next}/#{max_attempts}): #{e.message}"
+    end
+
+    def keep_trying?
+      return true  if current_attempt.zero?
+      return false if last_attempt?
+      return true  if @failed
+    end
+
+    def last_attempt?
+      current_attempt >= max_attempts
+    end
+  end
+end