[Source] Fix a crash when searching for compatible versions

Closes #482

CHANGELOG.md

@@ -8,7 +8,9 @@
 
 ##### Bug Fixes
 
-* None.  
+* Fix a crash when searching for a compatible version of a Source that has a higher version requirement  
+  [Eric Amorde](https://github.com/amorde)
+  [#482](https://github.com/CocoaPods/Core/issues/482)
 
 
 ## 1.7.0.beta.3 (2019-03-27)

lib/cocoapods-core/source/metadata.rb

@@ -53,7 +53,7 @@ def path_fragment(pod_name, version = nil)
       def last_compatible_version(target_version)
         return unless minimum_cocoapods_version
         return if minimum_cocoapods_version <= target_version
-        @last_compatible_versions.reverse_each.bsearch { |v| v <= target_version }.tap do |version|
+        Array(@last_compatible_versions.reverse_each).bsearch { |v| v <= target_version }.tap do |version|
           raise Informative, 'Unable to find compatible version' unless version
         end
       end

spec/source/metadata_spec.rb

@@ -39,6 +39,30 @@ module Pod
       end
     end
 
+    describe '#last_compatible_version' do
+      it 'returns the last compatible version if available' do
+        metadata_hash = {
+          'min' => '1.9.0',
+          'max' => '2.0.0',
+          'last_compatible_versions' => %w(1.0 1.4 2.0)
+        }
+        metadata = Source::Metadata.new(metadata_hash)
+        result = metadata.last_compatible_version(Version.new('1.5.0'))
+        result.should == Pod::Version.new('1.4.0')
+      end
+
+      it 'raises when unable to find a compatible version' do
+        metadata_hash = {
+          'min' => '2.0.0',
+          'max' => '2.0.0'
+        }
+        metadata = Source::Metadata.new(metadata_hash)
+        should.raise Pod::Informative do
+          metadata.last_compatible_version(Version.new('1.5.0'))
+        end.message.should.match /Unable to find compatible version/
+      end
+    end
+
     describe '#compatible?' do
       it 'returns whether a repository is compatible' do
         @metadata = Source::Metadata.new('min' => '0.0.1')