Better warning message for which Swift version was used during validation

CHANGELOG.md

@@ -30,6 +30,10 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 ##### Bug Fixes
 
+* Better warning message for which Swift version was used during validation  
+  [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
+  [#7121](https://github.com/CocoaPods/CocoaPods/issues/7121)
+
 * Strip vendored dSYMs during embed script phase  
   [Dimitris Koutsogiorgas](https://github.com/dnkoutso)
   [#7111](https://github.com/CocoaPods/CocoaPods/issues/7111)
@@ -139,7 +143,7 @@ To install release candidates run `[sudo] gem install cocoapods --pre`
 
 * Fix validation warnings when using --swift-version  
   [Danielle Tomlinson](https://github.com/dantoml)
-  [#6971](https://github.com/CocoaPods/CocoaPods/issue/6971)
+  [#6971](https://github.com/CocoaPods/CocoaPods/pull/6971)
 
 * Fix xcconfig boolean merging when substrings include yes or no  
   [Paul Beusterien](https://github.com/paulb777)

lib/cocoapods/generator/app_target_helper.rb

@@ -99,6 +99,7 @@ module Pod
       # @return [void]
       #
       def self.add_swift_version(target, swift_version)
+        raise 'Cannot set empty Swift version to target.' if swift_version.blank?
         target.build_configurations.each do |configuration|
           configuration.build_settings['SWIFT_VERSION'] = swift_version
         end

lib/cocoapods/validator.rb

@@ -256,7 +256,7 @@ module Pod
     # @return [String] the SWIFT_VERSION to use for validation.
     #
     def swift_version
-      return @swift_version if defined?(@swift_version)
+      return @swift_version unless @swift_version.nil?
       if version = dot_swift_version
         @swift_version = version
       else
@@ -277,11 +277,10 @@ module Pod
       swift_version_path.read.strip
     end
 
-    # @return [String] A string representing the Swift version used during linting
-    #                  or nil, if Swift was not used.
+    # @return [Boolean] Whether any of the pod targets part of this validator use Swift or not.
     #
-    def used_swift_version
-      swift_version if @installer.pod_targets.any?(&:uses_swift?)
+    def uses_swift?
+      @installer.pod_targets.any?(&:uses_swift?)
     end
 
     #-------------------------------------------------------------------------#
@@ -318,7 +317,7 @@ module Pod
           download_pod
           check_file_patterns
           install_pod
-          validate_dot_swift_version
+          validate_swift_version
           add_app_project_import
           validate_vendored_dynamic_frameworks
           build_pod
@@ -394,14 +393,21 @@ module Pod
       validate_url(spec.documentation_url) if spec.documentation_url
     end
 
-    def validate_dot_swift_version
-      if !used_swift_version.nil? && @swift_version.nil?
+    # Performs validation for which version of Swift is used during validation.
+    #
+    # The user will be warned that the default version of Swift was used if the following things are true:
+    #   - The project uses Swift at all
+    #   - The user did not supply a Swift version via a parameter
+    #   - There is no `.swift-version` file present either.
+    #
+    def validate_swift_version
+      if uses_swift? && @swift_version.nil? && dot_swift_version.nil?
         warning(:swift_version,
-                'The validator for Swift projects uses ' \
-                'Swift 3.0 by default, if you are using a different version of ' \
-                'swift you can use a `.swift-version` file to set the version for ' \
-                "your Pod. For example to use Swift 2.3, run: \n" \
-                '    `echo "2.3" > .swift-version`')
+                'The validator used ' \
+                "Swift #{DEFAULT_SWIFT_VERSION} by default because no Swift version was specified. " \
+                'If you want to use a different version of Swift during validation, then either use the `--swift-version` parameter ' \
+                'or use a `.swift-version` file to set the version of Swift to use for ' \
+                'your Pod. For example to use Swift 2.3, run: `echo "2.3" > .swift-version`.')
       end
     end
 

spec/unit/validator_spec.rb

@@ -885,11 +885,29 @@ module Pod
 
           result = validator.results.first
           result.type.should == :warning
-          result.message.should == 'The validator for ' \
-            'Swift projects uses Swift 3.0 by default, if you are using a ' \
-            'different version of swift you can use a `.swift-version` file ' \
-            'to set the version for your Pod. For example to use Swift 2.3, ' \
-            "run: \n    `echo \"2.3\" > .swift-version`"
+          result.message.should == 'The validator used ' \
+            'Swift 3.0 by default because no Swift version was specified. ' \
+            'If you want to use a different version of Swift during validation, then either use the `--swift-version` parameter ' \
+            'or use a `.swift-version` file to set the version of Swift to use for ' \
+            'your Pod. For example to use Swift 2.3, run: `echo "2.3" > .swift-version`.'
+        end
+
+        it 'does not warn for Swift if version was set by a dot swift version file' do
+          Specification.any_instance.stubs(:deployment_target).returns('9.0')
+
+          validator = test_swiftpod_with_dot_swift_version
+          validator.validate
+          validator.results.count.should == 0
+        end
+
+        it 'does not warn for Swift if version was set as a parameter' do
+          Specification.any_instance.stubs(:deployment_target).returns('9.0')
+
+          validator = test_swiftpod
+          validator.stubs(:dot_swift_version).returns(nil)
+          validator.swift_version = '3.1.0'
+          validator.validate
+          validator.results.count.should == 0
         end
       end
 
@@ -950,7 +968,7 @@ module Pod
           validator.instance_variable_set(:@installer, installer)
 
           validator.stubs(:dot_swift_version).returns('1.2.3')
-          validator.used_swift_version.should == '1.2.3'
+          validator.uses_swift?.should.be.true
         end
 
         it 'returns the swift_version when a target has used Swift' do
@@ -959,7 +977,7 @@ module Pod
           installer = stub(:pod_targets => [pod_target])
           validator.instance_variable_set(:@installer, installer)
 
-          validator.used_swift_version.should.nil?
+          validator.uses_swift?.should.be.false
         end
       end
     end