Merge branch 'better-go-modules-error-handling'

lib/dependabot/file_parsers/go/modules/go_mod_parser.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "open3"
 require "dependabot/dependency"
 require "dependabot/file_parsers/base/dependency_set"
 require "dependabot/file_parsers/go/modules"
@@ -66,16 +67,28 @@ def dependency_from_details(details)
 
           def module_info(go_mod)
             @module_info ||=
-              SharedHelpers.in_a_temporary_directory do
+              SharedHelpers.in_a_temporary_directory do |path|
                 SharedHelpers.with_git_configured(credentials: credentials) do
                   File.write("go.mod", go_mod.content)
 
-                  output = `GO111MODULE=on go list -m -json all`
-                  unless $CHILD_STATUS.success?
-                    raise Dependabot::DependencyFileNotParseable, go_mod.path
+                  command = "GO111MODULE=on go list -m -json all"
+                  stdout, stderr, status = Open3.capture3(command)
+                  next stdout if status.success?
+
+                  case stderr
+                  when /go: .*: unknown revision/
+                    error_msg = stderr.lines.grep(/unknown revision/).first
+                    raise Dependabot::DependencyFileNotResolvable, error_msg
+                  when /go: .*: unrecognized import path/
+                    error_msg = stderr.lines.grep(/unrecognized import/).first
+                    raise Dependabot::DependencyFileNotResolvable, error_msg
+                  when /go: errors parsing go.mod/
+                    error_msg = stderr.gsub(path.to_s, "")
+                    raise Dependabot::DependencyFileNotParseable, error_msg
+                  else
+                    error_msg = stderr.gsub(path.to_s, "")
+                    raise Dependabot::DependencyFileNotParseable, error_msg
                   end
-
-                  output
                 end
               end
           end

spec/dependabot/file_parsers/go/modules/go_mod_parser_spec.rb

@@ -21,9 +21,10 @@
   let(:go_mod) do
     Dependabot::DependencyFile.new(
       name: "go.mod",
-      content: fixture("go", "go_mods", go_mod_fixture_name)
+      content: go_mod_content
     )
   end
+  let(:go_mod_content) { fixture("go", "go_mods", go_mod_fixture_name) }
   let(:go_mod_fixture_name) { "go.mod" }
 
   describe "dependency_set" do
@@ -114,5 +115,38 @@
         end
       end
     end
+
+    describe "a garbage go.mod" do
+      let(:go_mod_content) { "not really a go.mod file :-/" }
+
+      it "raises the correct error" do
+        expect { parser.dependency_set }.
+          to raise_error(Dependabot::DependencyFileNotParseable)
+      end
+    end
+
+    describe "a non-existent dependency" do
+      let(:go_mod_content) do
+        go_mod = fixture("go", "go_mods", go_mod_fixture_name)
+        go_mod.sub("rsc.io/quote", "example.com/not-a-repo")
+      end
+
+      it "raises the correct error" do
+        expect { parser.dependency_set }.
+          to raise_error(Dependabot::DependencyFileNotResolvable)
+      end
+    end
+
+    describe "a dependency at a non-existent version" do
+      let(:go_mod_content) do
+        go_mod = fixture("go", "go_mods", go_mod_fixture_name)
+        go_mod.sub("rsc.io/quote v1.4.0", "rsc.io/quote v1.321.0")
+      end
+
+      it "raises the correct error" do
+        expect { parser.dependency_set }.
+          to raise_error(Dependabot::DependencyFileNotResolvable)
+      end
+    end
   end
 end