Add support for disablePackageSources in NuGet.Config

nuget/lib/dependabot/nuget/update_checker/repository_finder.rb

@@ -166,6 +166,11 @@ def repos_from_config_file(config_file)
               }
             end
 
+          disabled_sources = disabled_sources(doc)
+          sources.reject! do |s|
+            disabled_sources.include?(s[:key])
+          end
+
           unless doc.css("configuration > packageSources > clear").any?
             sources << { url: DEFAULT_REPOSITORY_URL, key: nil }
           end
@@ -198,6 +203,20 @@ def default_repository_details
           }
         end
 
+        # rubocop:disable Metrics/PerceivedComplexity
+        def disabled_sources(doc)
+          doc.css("configuration > disabledPackageSources > add").map do |node|
+            value = node.attribute("value")&.value ||
+                    node.at_xpath("./value")&.content
+
+            if value&.strip&.downcase == "true"
+              node.attribute("key")&.value&.strip ||
+                node.at_xpath("./key")&.content&.strip
+            end
+          end
+        end
+        # rubocop:enable Metrics/PerceivedComplexity
+
         # rubocop:disable Metrics/PerceivedComplexity
         def add_config_file_credentials(sources:, doc:)
           sources.each do |source_details|

nuget/spec/dependabot/nuget/update_checker/repository_finder_spec.rb

@@ -253,6 +253,27 @@
             )
           end
         end
+
+        context "that has disabled package sources" do
+          let(:config_file_fixture_name) { "disabled_sources.config" }
+
+          it "only includes the enabled package sources" do
+            expect(dependency_urls).to match_array(
+              [{
+                repository_url: "https://www.myget.org/F/exceptionless/api/v3/"\
+                                "index.json",
+                versions_url: "https://www.myget.org/F/exceptionless/api/v3/"\
+                                "flatcontainer/microsoft.extensions."\
+                                "dependencymodel/index.json",
+                search_url: "https://www.myget.org/F/exceptionless/api/v3/"\
+                                "query?q=microsoft.extensions.dependencymodel"\
+                                "&prerelease=true",
+                auth_header: { "Authorization" => "Basic bXk6cGFzc3cwcmQ=" },
+                repository_type: "v3"
+              }]
+            )
+          end
+        end
       end
 
       context "that has a numeric key" do

nuget/spec/fixtures/configs/disabled_sources.config

@@ -0,0 +1,72 @@
+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+    <config>
+        <!--
+            Used to specify the default location to expand packages.
+            See: nuget.exe help install
+            See: nuget.exe help update
+
+            In this example, %PACKAGEHOME% is an environment variable. On Mac/Linux,
+            use $PACKAGE_HOME/External as the value.
+        -->
+        <add key="repositoryPath" value="%PACKAGEHOME%\External" />
+
+        <!--
+            Used to specify default source for the push command.
+            See: nuget.exe help push
+        -->
+
+        <add key="defaultPushSource" value="https://MyRepo/ES/api/v2/package" />
+
+        <!-- Proxy settings -->
+        <add key="http_proxy" value="host" />
+        <add key="http_proxy.user" value="username" />
+        <add key="http_proxy.password" value="encrypted_password" />
+    </config>
+
+    <packageRestore>
+        <!-- Allow NuGet to download missing packages -->
+        <add key="enabled" value="True" />
+
+        <!-- Automatically check for missing packages during build in Visual Studio -->
+        <add key="automatic" value="True" />
+    </packageRestore>
+
+    <!--
+        Used to specify the default Sources for list, install and update.
+        See: nuget.exe help list
+        See: nuget.exe help install
+        See: nuget.exe help update
+    -->
+    <packageSources>
+        <clear />
+        <add key="MyRepo - ES" value="https://www.myget.org/F/exceptionless/api/v3/index.json" />
+        <add key="Local repo" value="lib" />
+        <add key="Some disabled source" value="https://disabled.example/api/v3/index.json" />
+    </packageSources>
+
+    <!-- Used to store credentials -->
+    <packageSourceCredentials>
+        <MyRepo_x0020_-_x0020_ES>
+            <add key="Username" value="my" />
+            <add key="ClearTextPassword" value="passw0rd" />
+        </Test_x0020_Source>
+    </packageSourceCredentials>
+
+    <!-- Used to disable package sources  -->
+    <disabledPackageSources>
+        <add key="Some disabled source" value="true" />
+        <add key="missing source" value="true" />
+        <add key="MyRepo - ES" value="false" />
+    </disabledPackageSources>
+
+    <!--
+        Used to specify default API key associated with sources.
+        See: nuget.exe help setApiKey
+        See: nuget.exe help push
+        See: nuget.exe help mirror
+    -->
+    <apikeys>
+        <add key="https://MyRepo/ES/api/v2/package" value="encrypted_api_key" />
+    </apikeys>
+</configuration>