From 9789762a2ddbdb71a060abf484c53e6512911fb8 Mon Sep 17 00:00:00 2001
From: "Marcelo E. Magallon" <marcelo.magallon@grafana.com>
Date: Mon, 2 Aug 2021 10:37:13 -0600
Subject: [PATCH] Add helper method to config.Secret to load a file

LoadFromFile is a very small helper to avoid repeating this code over
and over again.

This is related to prometheus/prometheus#8551

Signed-off-by: Marcelo E. Magallon <marcelo.magallon@grafana.com>
---
 config/config.go           | 11 ++++++++
 config/config_test.go      | 55 ++++++++++++++++++++++++++++++++++++++
 config/http_config.go      |  1 +
 config/http_config_test.go |  1 +
 config/tls_config_test.go  |  1 +
 expfmt/fuzz.go             |  1 +
 6 files changed, 70 insertions(+)

diff --git a/config/config.go b/config/config.go
index fffda4a7..f773b7c6 100644
--- a/config/config.go
+++ b/config/config.go
@@ -18,6 +18,8 @@ package config
 
 import (
 	"encoding/json"
+	"fmt"
+	"io/ioutil"
 	"path/filepath"
 )
 
@@ -48,6 +50,15 @@ func (s Secret) MarshalJSON() ([]byte, error) {
 	return json.Marshal(secretToken)
 }
 
+func (s *Secret) LoadFromFile(filename string) error {
+	buf, err := ioutil.ReadFile(filename)
+	if err != nil {
+		return fmt.Errorf("cannot read %s: %w", filename, err)
+	}
+	*s = Secret(buf)
+	return nil
+}
+
 // DirectorySetter is a config type that contains file paths that may
 // be relative to the file containing the config.
 type DirectorySetter interface {
diff --git a/config/config_test.go b/config/config_test.go
index 81c78555..89794d4e 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -11,12 +11,15 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.8
 // +build go1.8
 
 package config
 
 import (
 	"encoding/json"
+	"io/ioutil"
+	"os"
 	"testing"
 )
 
@@ -53,3 +56,55 @@ func TestJSONMarshalSecret(t *testing.T) {
 		})
 	}
 }
+
+func TestSecretLoadFromFile(t *testing.T) {
+	dn, err := ioutil.TempDir("", "test-secret-loadfromfile.")
+	if err != nil {
+		t.Fatalf("cannot create temporary directory: %s", err)
+	}
+	defer os.RemoveAll(dn)
+
+	fh, err := ioutil.TempFile(dn, "")
+	if err != nil {
+		t.Fatalf("cannot create temporary file: %s", err)
+	}
+
+	fn := fh.Name()
+
+	secretData := "test"
+
+	n, err := fh.WriteString(secretData)
+	if err != nil {
+		t.Fatalf("cannot write to temporary file %s: %s", fn, err)
+	}
+
+	if n != len(secretData) {
+		t.Fatalf("short write writing to temporary file %s, expecting %d, got %d", fn, len(secretData), n)
+	}
+
+	err = fh.Close()
+	if err != nil {
+		t.Fatalf("error closing temporary file %s after write: %s", fn, err)
+	}
+
+	var s Secret
+	err = s.LoadFromFile(fn)
+	if err != nil {
+		t.Fatalf("cannot read secret from temporary file %s: %s", fn, err)
+	}
+
+	if string(s) != secretData {
+		t.Fatalf("unexpected secret data, expected %q, actual %q", secretData, string(s))
+	}
+
+	err = os.Remove(fn)
+	if err != nil {
+		t.Fatalf("cannot remove temporary file %s: %s", fn, err)
+	}
+
+	// this should report an error now
+	err = s.LoadFromFile(fn)
+	if err == nil {
+		t.Fatalf("expecting error reading non-existent temporary file %s, got nil", fn)
+	}
+}
diff --git a/config/http_config.go b/config/http_config.go
index 8c07c41f..11bb9bfe 100644
--- a/config/http_config.go
+++ b/config/http_config.go
@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.8
 // +build go1.8
 
 package config
diff --git a/config/http_config_test.go b/config/http_config_test.go
index 689bbde2..b02f8ede 100644
--- a/config/http_config_test.go
+++ b/config/http_config_test.go
@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.8
 // +build go1.8
 
 package config
diff --git a/config/tls_config_test.go b/config/tls_config_test.go
index 57ad4bb4..bd8add67 100644
--- a/config/tls_config_test.go
+++ b/config/tls_config_test.go
@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.8
 // +build go1.8
 
 package config
diff --git a/expfmt/fuzz.go b/expfmt/fuzz.go
index dc2eedee..f819e4f8 100644
--- a/expfmt/fuzz.go
+++ b/expfmt/fuzz.go
@@ -12,6 +12,7 @@
 // limitations under the License.
 
 // Build only when actually fuzzing
+//go:build gofuzz
 // +build gofuzz
 
 package expfmt