Auto merge of #5443 - bundler:seg-resolver-sorting, r=indirect

[Resolver] Improve sorting of deps with 0 or 1 possibility

As the added comment says, this will force all dependencies where there are only 0 or 1 total specs with that name to be resolved first. Right now, they sort ~last, which leads to poor performance.

(This was one way of fixing some recent resolver issues, even though we've done the proper fixes in Molinillo for them)

(cherry picked from commit cc4414ca7cfe76989ecbefec8408e2c26cdaf71d)

2 files changed, 13 insertions, 9 deletions

diff --git a/lib/bundler/resolver.rb b/lib/bundler/resolver.rb
index 2bdf4721ec..cdf2419c42 100644
--- a/lib/bundler/resolver.rb
+++ b/lib/bundler/resolver.rb
@@ -230,11 +230,11 @@ module Bundler
 
     def debug?
       return @debug_mode if defined?(@debug_mode)
-      @debug_mode = ENV["DEBUG_RESOLVER"] || ENV["DEBUG_RESOLVER_TREE"]
+      @debug_mode = ENV["DEBUG_RESOLVER"] || ENV["DEBUG_RESOLVER_TREE"] || false
     end
 
     def before_resolution
-      Bundler.ui.info "Resolving dependencies...", false
+      Bundler.ui.info "Resolving dependencies...", debug?
     end
 
     def after_resolution
@@ -242,7 +242,7 @@ module Bundler
     end
 
     def indicate_progress
-      Bundler.ui.info ".", false
+      Bundler.ui.info ".", false unless debug?
     end
 
     include Molinillo::SpecificationProvider
@@ -328,6 +328,12 @@ module Bundler
 
   private
 
+    # returns an integer \in (-\infty, 0]
+    # a number closer to 0 means the dependency is less constraining
+    #
+    # dependencies w/ 0 or 1 possibilities (ignoring version requirements)
+    # are given very negative values, so they _always_ sort first,
+    # before dependencies that are unconstrained
     def amount_constrained(dependency)
       @amount_constrained ||= {}
       @amount_constrained[dependency.name] ||= begin
@@ -335,8 +341,9 @@ module Bundler
           dependency.requirement.satisfied_by?(base.first.version) ? 0 : 1
         else
           all = index_for(dependency).search(dependency.name).size
+
           if all <= 1
-            all
+            all - 1_000_000
           else
             search = search_for(dependency).size
             search - all
diff --git a/spec/install/bundler_spec.rb b/spec/install/bundler_spec.rb
index 9f06a48086..e7f308e188 100644
--- a/spec/install/bundler_spec.rb
+++ b/spec/install/bundler_spec.rb
@@ -44,17 +44,14 @@ describe "bundle install" do
           In Gemfile:
             bundler (= 0.9.2)
 
-            rails (= 3.0) was resolved to 3.0, which depends on
-              bundler (>= 0.9.0.pre)
-
           Current Bundler version:
             bundler (#{Bundler::VERSION})
         This Gemfile requires a different version of Bundler.
         Perhaps you need to update Bundler by running `gem install bundler`?
 
-        Could not find gem 'bundler (= 0.9.2)', which is required by gem 'rails (= 3.0)', in any of the sources.
+        Could not find gem 'bundler (= 0.9.2)' in any of the sources
         E
-      expect(out).to include(nice_error)
+      expect(out).to eq(nice_error)
     end
 
     it "works for gems with multiple versions in its dependencies" do