Improve detection of unsupported cargo toolchains

cargo/lib/dependabot/cargo/file_updater/lockfile_updater.rb

@@ -146,7 +146,7 @@ def run_shell_command(command, fingerprint:)
           # returns a non-zero status
           return if process.success?
 
-          if stdout.include?("usage of sparse registries requires `-Z sparse-registry`")
+          if using_old_toolchain?(stdout)
             raise Dependabot::DependencyFileNotEvaluatable, "Dependabot only supports toolchain 1.68 and up."
           end
 
@@ -170,6 +170,15 @@ def run_shell_command(command, fingerprint:)
           )
         end
 
+        def using_old_toolchain?(message)
+          return true if message.include?("usage of sparse registries requires `-Z sparse-registry`")
+
+          version_log = /rust version (?<version>\d.\d+)/.match(message)
+          return false unless version_log
+
+          version_class.new(version_log[:version]) < version_class.new("1.68")
+        end
+
         def write_temporary_dependency_files
           write_temporary_manifest_files
           write_temporary_path_dependency_files
@@ -386,6 +395,10 @@ def toolchain
         def virtual_manifest?(file)
           !file.content.include?("[package]")
         end
+
+        def version_class
+          dependency.version_class
+        end
       end
     end
   end

cargo/lib/dependabot/cargo/update_checker/version_resolver.rb

@@ -238,17 +238,26 @@ def handle_cargo_errors(error)
             return nil
           end
 
-          if error.message.include?("usage of sparse registries requires `-Z sparse-registry`")
+          if using_old_toolchain?(error.message)
             raise Dependabot::DependencyFileNotEvaluatable, "Dependabot only supports toolchain 1.68 and up."
           end
 
           raise Dependabot::DependencyFileNotResolvable, error.message if resolvability_error?(error.message)
 
-          raise error
+          raise
         end
         # rubocop:enable Metrics/AbcSize
         # rubocop:enable Metrics/PerceivedComplexity
 
+        def using_old_toolchain?(message)
+          return true if message.include?("usage of sparse registries requires `-Z sparse-registry`")
+
+          version_log = /rust version (?<version>\d.\d+)/.match(message)
+          return false unless version_log
+
+          version_class.new(version_log[:version]) < version_class.new("1.68")
+        end
+
         def unreachable_git_urls
           return @unreachable_git_urls if defined?(@unreachable_git_urls)
 
@@ -295,7 +304,11 @@ def resolvability_error?(message)
           return true if message.match?(/feature `[^\`]+` is required/)
           return true if message.include?("unexpected end of input while parsing major version number")
 
-          !original_requirements_resolvable?
+          original_requirements_resolvable = original_requirements_resolvable?
+
+          return false if original_requirements_resolvable == :unknown
+
+          !original_requirements_resolvable
         end
 
         def original_requirements_resolvable?
@@ -310,13 +323,15 @@ def original_requirements_resolvable?
 
           true
         rescue SharedHelpers::HelperSubprocessFailed => e
-          raise unless e.message.include?("no matching version") ||
-                       e.message.include?("failed to select a version") ||
-                       e.message.include?("no matching package named") ||
-                       e.message.include?("failed to parse manifest") ||
-                       e.message.include?("failed to update submodule")
-
-          false
+          if e.message.include?("no matching version") ||
+             e.message.include?("failed to select a version") ||
+             e.message.include?("no matching package named") ||
+             e.message.include?("failed to parse manifest") ||
+             e.message.include?("failed to update submodule")
+            false
+          else
+            :unknown
+          end
         end
 
         def workspace_native_library_update_error?(message)