GitHub #8: Seed indexes from index.yml

service/datastore/datastore.go

Index: service/datastore/datastore.go
diff --git a/service/datastore/datastore.go b/service/datastore/datastore.go
index 68fae10a88300f0fe0773b21bfb45a09654af4a1..0389ab8914415b197f88abc87911eb05541587b9 100644
--- a/service/datastore/datastore.go
+++ b/service/datastore/datastore.go
@@ -6,9 +6,17 @@ package datastore
 
 import (
 	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
 	"reflect"
+	"runtime"
+	"strings"
 
 	"github.com/luci/luci-go/common/errors"
+
+	"gopkg.in/yaml.v2"
 )
 
 type datastoreImpl struct {
@@ -348,3 +356,86 @@ func (d *datastoreImpl) DeleteMulti(keys []*Key) (err error) {
 func (d *datastoreImpl) Raw() RawInterface {
 	return d.RawInterface
 }
+
+// ParseIndexYAML parses the contents of a index YAML file into a list of
+// IndexDefinitions.
+func ParseIndexYAML(content io.Reader) ([]*IndexDefinition, error) {
+	serialized, err := ioutil.ReadAll(content)
+	if err != nil {
+		return nil, err
+	}
+
+	var m map[string][]*IndexDefinition
+	if err := yaml.Unmarshal(serialized, &m); err != nil {
+		return nil, err
+	}
+
+	if _, ok := m["indexes"]; !ok {
+		return nil, fmt.Errorf("datastore: missing key `indexes`: %v", m)
+	}
+	return m["indexes"], nil
+}
+
+// getCallingTestFilePath looks up the call stack until the specified
+// maxStackDepth and returns the absolute path of the first source filename
+// ending with `_test.go`. If no test file is found, getCallingTestFilePath
+// returns a non-nil error.
+func getCallingTestFilePath(maxStackDepth int) (string, error) {
+	pcs := make([]uintptr, maxStackDepth)
+
+	for _, pc := range pcs[:runtime.Callers(0, pcs)] {
+		path, _ := runtime.FuncForPC(pc - 1).FileLine(pc - 1)
+		if filename := filepath.Base(path); strings.HasSuffix(filename, "_test.go") {
+			return path, nil
+		}
+	}
+
+	return "", fmt.Errorf("datastore: failed to determine source file name")
+}
+
+// FindAndParseIndexYAML walks up from the directory specified by path until it
+// finds a `index.yaml` or `index.yml` file. If an index YAML file
+// is found, it opens and parses the file, and returns all the indexes found.
+// If path is a relative path, it is converted into an absolute path
+// relative to the calling test file. To determine the path of the calling test
+// file, FindAndParseIndexYAML walks upto a maximum of 100 call stack frames
+// looking for a file ending with `_test.go`.
+//
+// FindAndParseIndexYAML returns a non-nil error if the root of the drive is
+// reached without finding an index YAML file, if there was
+// an error reading the found index YAML file, or if the calling test file could
+// not be located in the case of a relative path argument.
+func FindAndParseIndexYAML(path string) ([]*IndexDefinition, error) {
+	var currentDir string
+
+	if filepath.IsAbs(path) {
+		currentDir = path
+	} else {
+		testPath, err := getCallingTestFilePath(100)
+		if err != nil {
+			return nil, err
+		}
+		currentDir = filepath.Join(filepath.Dir(testPath), path)
+	}
+
+	isRoot := func(dir string) bool {
+		parentDir := filepath.Dir(dir)
+		return os.IsPathSeparator(dir[len(dir)-1]) && os.IsPathSeparator(parentDir[len(parentDir)-1])
+	}
+
+	for {
+		for _, filename := range []string{"index.yml", "index.yaml"} {
+			file, err := os.Open(filepath.Join(currentDir, filename))
+			if err == nil {
+				defer file.Close()
+				return ParseIndexYAML(file)
+			}
+		}
+
+		if isRoot(currentDir) {
+			return nil, fmt.Errorf("datastore: failed to find index YAML file")
+		}
+
+		currentDir = filepath.Dir(currentDir)
+	}
+}