Enforce only one CODEOWNERS file (#100)

* Enforce only one CODEOWNERS file

* Adjust code before merging to support more verbose err messages

Co-authored-by: Mateusz Szostok <szostok.mateusz@gmail.com>

go.mod

@@ -24,6 +24,8 @@ require (
 	gotest.tools v2.2.0+incompatible
 )
 
+require github.com/dustin/go-humanize v1.0.0
+
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/emirpasic/gods v1.12.0 // indirect

go.sum

@@ -57,6 +57,8 @@ github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ3
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/dustin/go-humanize v1.0.0 h1:VSnTsYCnlFHaM2/igO1h6X3HA71jcobQuxemgkq4zYo=
+github.com/dustin/go-humanize v1.0.0/go.mod h1:HtrtbFcZ19U5GC7JDqmcUSB87Iq5E25KnS6fMYU6eOk=
 github.com/emirpasic/gods v1.12.0 h1:QAUIPSaCu4G+POclxeqb3F+WPpdKqFGlw36+yOzGlrg=
 github.com/emirpasic/gods v1.12.0/go.mod h1:YfzfFFoVP/catgzJb4IKIqXjX78Ha8FMSDh3ymbK86o=
 github.com/envoyproxy/go-control-plane v0.9.0/go.mod h1:YTl/9mNaCwkRvm6d1a2C3ymFceY/DCBVvsKhRF0iEA4=

pkg/codeowners/owners.go

@@ -8,6 +8,7 @@ import (
 	"path"
 	"strings"
 
+	"github.com/dustin/go-humanize/english"
 	"github.com/spf13/afero"
 )
 
@@ -38,6 +39,7 @@ func NewFromPath(path string) ([]Entry, error) {
 // openCodeownersFile finds a CODEOWNERS file and returns content.
 // see: https://help.github.com/articles/about-code-owners/#codeowners-file-location
 func openCodeownersFile(dir string) (io.Reader, error) {
+	var detectedFiles []string
 	for _, p := range []string{".", "docs", ".github"} {
 		pth := path.Join(dir, p)
 		exists, err := afero.DirExists(fs, pth)
@@ -59,10 +61,26 @@ func openCodeownersFile(dir string) (io.Reader, error) {
 			return nil, err
 		}
 
-		return fs.Open(f)
+		detectedFiles = append(detectedFiles, f)
 	}
 
-	return nil, fmt.Errorf("No CODEOWNERS found in the root, docs/, or .github/ directory of the repository %s", dir)
+	switch l := len(detectedFiles); l {
+	case 0:
+		return nil, fmt.Errorf("No CODEOWNERS found in the root, docs/, or .github/ directory of the repository %s", dir)
+	case 1:
+		return fs.Open(detectedFiles[0])
+	default:
+		return nil, fmt.Errorf("Multiple CODEOWNERS files found in the %s locations of the repository %s",
+			english.OxfordWordSeries(replacePrefix(detectedFiles, dir, "./"), "and"),
+			dir)
+	}
+}
+
+func replacePrefix(in []string, prefix string, s string) []string {
+	for idx := range in {
+		in[idx] = fmt.Sprintf("%s%s", s, strings.TrimPrefix(in[idx], prefix))
+	}
+	return in
 }
 
 func ParseCodeowners(r io.Reader) []Entry {

pkg/codeowners/owners_test.go

@@ -113,3 +113,52 @@ func TestFindCodeownersFileFailure(t *testing.T) {
 	assert.EqualError(t, err, expErrMsg)
 	assert.Nil(t, entries)
 }
+
+func TestMultipleCodeownersFileFailure(t *testing.T) {
+	const givenRepoPath = "/workspace/go/repo-without-codeowners/"
+	tests := map[string]struct {
+		expErrMsg                string
+		givenCodeownersLocations []string
+	}{
+		"Should report that no CODEOWNERS file was found": {
+			expErrMsg:                fmt.Sprintf("No CODEOWNERS found in the root, docs/, or .github/ directory of the repository %s", givenRepoPath),
+			givenCodeownersLocations: nil,
+		},
+		"Should report that CODEOWNERS file was found on root and docs/": {
+			expErrMsg:                fmt.Sprintf("Multiple CODEOWNERS files found in the ./CODEOWNERS and ./docs/CODEOWNERS locations of the repository %s", givenRepoPath),
+			givenCodeownersLocations: []string{"CODEOWNERS", path.Join("docs", "CODEOWNERS")},
+		},
+		"Should report that CODEOWNERS file was found on root and .github/": {
+			expErrMsg:                fmt.Sprintf("Multiple CODEOWNERS files found in the ./CODEOWNERS and ./.github/CODEOWNERS locations of the repository %s", givenRepoPath),
+			givenCodeownersLocations: []string{"CODEOWNERS", path.Join(".github/", "CODEOWNERS")},
+		},
+		"Should report that CODEOWNERS file was found in docs/ and .github/": {
+			expErrMsg:                fmt.Sprintf("Multiple CODEOWNERS files found in the ./docs/CODEOWNERS and ./.github/CODEOWNERS locations of the repository %s", givenRepoPath),
+			givenCodeownersLocations: []string{path.Join(".github", "CODEOWNERS"), path.Join("docs", "CODEOWNERS")},
+		},
+		"Should report that CODEOWNERS file was found on root, docs/ and .github/": {
+			expErrMsg:                fmt.Sprintf("Multiple CODEOWNERS files found in the ./CODEOWNERS, ./docs/CODEOWNERS, and ./.github/CODEOWNERS locations of the repository %s", givenRepoPath),
+			givenCodeownersLocations: []string{"CODEOWNERS", path.Join(".github", "CODEOWNERS"), path.Join("docs", "CODEOWNERS")},
+		},
+	}
+	for tn, tc := range tests {
+		t.Run(tn, func(t *testing.T) {
+			// given
+			tFS := afero.NewMemMapFs()
+			revert := codeowners.SetFS(tFS)
+			defer revert()
+
+			for _, location := range tc.givenCodeownersLocations {
+				_, err := tFS.Create(path.Join(givenRepoPath, location))
+				require.NoError(t, err)
+			}
+
+			// when
+			entries, err := codeowners.NewFromPath(givenRepoPath)
+
+			// then
+			assert.EqualError(t, err, tc.expErrMsg)
+			assert.Nil(t, entries)
+		})
+	}
+}