From 508afe2c26737e0be60a72faa9d6740a06b0914c Mon Sep 17 00:00:00 2001
From: Ellen Marie Dash <the@smallest.dog>
Date: Sat, 17 Aug 2019 04:45:09 +0000
Subject: [rubygems/rubygems] Set SOURCE_DATE_EPOCH env var if not provided.

Fixes #2290.

1. `Gem::Specification.date` returns SOURCE_DATE_EPOCH when defined,
2. this commit makes RubyGems set it _persistently_ when not provided.

This combination means that you can build a gem, check the build time,
and use that value to generate a new build -- and then verify they're
the same.

https://github.com/rubygems/rubygems/commit/d830d53f59
---
 lib/rubygems.rb                    | 17 +++++++++++++++++
 lib/rubygems/package.rb            |  2 +-
 lib/rubygems/package/tar_writer.rb |  8 ++++----
 lib/rubygems/specification.rb      |  2 +-
 4 files changed, 23 insertions(+), 6 deletions(-)

(limited to 'lib')

diff --git a/lib/rubygems.rb b/lib/rubygems.rb
index 4d06d98fdf..2676fbd3db 100644
--- a/lib/rubygems.rb
+++ b/lib/rubygems.rb
@@ -1242,6 +1242,23 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
 
   end
 
+  ##
+  # The SOURCE_DATE_EPOCH environment variable (or, if that's not set, the current time), converted to Time object.
+  # This is used throughout RubyGems for enabling reproducible builds.
+  #
+  # If it is not set as an environment variable already, this also sets it.
+  #
+  # Details on SOURCE_DATE_EPOCH:
+  # https://reproducible-builds.org/specs/source-date-epoch/
+
+  def self.source_date_epoch
+    if ENV["SOURCE_DATE_EPOCH"].nil? || ENV["SOURCE_DATE_EPOCH"].empty?
+      ENV["SOURCE_DATE_EPOCH"] = Time.now.to_i.to_s
+    end
+
+    Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc.freeze
+  end
+
   # FIX: Almost everywhere else we use the `def self.` way of defining class
   # methods, and then we switch over to `class << self` here. Pick one or the
   # other.
diff --git a/lib/rubygems/package.rb b/lib/rubygems/package.rb
index 16cda5affe..bef37aedc1 100644
--- a/lib/rubygems/package.rb
+++ b/lib/rubygems/package.rb
@@ -193,7 +193,7 @@ class Gem::Package
   def initialize(gem, security_policy) # :notnew:
     @gem = gem
 
-    @build_time      = ENV["SOURCE_DATE_EPOCH"] ? Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc : Time.now
+    @build_time      = Gem.source_date_epoch
     @checksums       = {}
     @contents        = nil
     @digests         = Hash.new { |h, algorithm| h[algorithm] = {} }
diff --git a/lib/rubygems/package/tar_writer.rb b/lib/rubygems/package/tar_writer.rb
index 87ee39a944..96d8184e8e 100644
--- a/lib/rubygems/package/tar_writer.rb
+++ b/lib/rubygems/package/tar_writer.rb
@@ -123,7 +123,7 @@ class Gem::Package::TarWriter
 
     header = Gem::Package::TarHeader.new :name => name, :mode => mode,
                                          :size => size, :prefix => prefix,
-                                         :mtime => ENV["SOURCE_DATE_EPOCH"] ? Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc : Time.now
+                                         :mtime => Gem.source_date_epoch
 
     @io.write header
     @io.pos = final_pos
@@ -217,7 +217,7 @@ class Gem::Package::TarWriter
 
     header = Gem::Package::TarHeader.new(:name => name, :mode => mode,
                                          :size => size, :prefix => prefix,
-                                         :mtime => ENV["SOURCE_DATE_EPOCH"] ? Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc : Time.now).to_s
+                                         :mtime => Gem.source_date_epoch).to_s
 
     @io.write header
     os = BoundedStream.new @io, size
@@ -245,7 +245,7 @@ class Gem::Package::TarWriter
                                          :size => 0, :typeflag => "2",
                                          :linkname => target,
                                          :prefix => prefix,
-                                         :mtime => ENV["SOURCE_DATE_EPOCH"] ? Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc : Time.now).to_s
+                                         :mtime => Gem.source_date_epoch).to_s
 
     @io.write header
 
@@ -298,7 +298,7 @@ class Gem::Package::TarWriter
     header = Gem::Package::TarHeader.new :name => name, :mode => mode,
                                          :typeflag => "5", :size => 0,
                                          :prefix => prefix,
-                                         :mtime => ENV["SOURCE_DATE_EPOCH"] ? Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc : Time.now
+                                         :mtime => Gem.source_date_epoch
 
     @io.write header
 
diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index c023e4f4aa..b3db311cbf 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -1667,7 +1667,7 @@ class Gem::Specification < Gem::BasicSpecification
   # https://reproducible-builds.org/specs/source-date-epoch/
 
   def date
-    @date ||= ENV["SOURCE_DATE_EPOCH"] ? Time.utc(*Time.at(ENV["SOURCE_DATE_EPOCH"].to_i).utc.to_a[3..5].reverse) : TODAY
+    @date ||= Time.utc(*Gem.source_date_epoch.utc.to_a[3..5].reverse)
   end
 
   DateLike = Object.new # :nodoc:
-- 
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