loader: read from file if ConfigFile.Content is empty (#315)

Fixes #314.

Signed-off-by: Andy Walker <walkeraj@gmail.com>

loader/loader.go

@@ -167,6 +167,13 @@ func Load(configDetails types.ConfigDetails, options ...func(*Options)) (*types.
 	for i, file := range configDetails.ConfigFiles {
 		configDict := file.Config
 		if configDict == nil {
+			if len(file.Content) == 0 {
+				content, err := os.ReadFile(file.Filename)
+				if err != nil {
+					return nil, err
+				}
+				file.Content = content
+			}
 			dict, err := parseConfig(file.Content, opts)
 			if err != nil {
 				return nil, err

loader/loader_test.go

@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"fmt"
 	"os"
+	"path/filepath"
 	"sort"
 	"strings"
 	"testing"
@@ -270,6 +271,32 @@ func TestLoad(t *testing.T) {
 	assert.Check(t, is.DeepEqual(sampleConfig.Volumes, actual.Volumes))
 }
 
+func TestLoadFromFile(t *testing.T) {
+	workingDir, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("os.Getwd(): %s", err)
+	}
+	tmpdir := t.TempDir()
+	tmpPath := filepath.Join(tmpdir, "Docker-compose.yaml")
+	if err := os.WriteFile(tmpPath, []byte(sampleYAML), 0444); err != nil {
+		t.Fatalf("failed to write temporary file: %s", err)
+	}
+	actual, err := Load(types.ConfigDetails{
+		WorkingDir: workingDir,
+		ConfigFiles: []types.ConfigFile{{
+			Filename: tmpPath,
+		}},
+		Environment: nil,
+	}, func(options *Options) {
+		options.SkipNormalization = true
+		options.SkipConsistencyCheck = true
+	})
+	assert.NilError(t, err)
+	assert.Check(t, is.DeepEqual(serviceSort(sampleConfig.Services), serviceSort(actual.Services)))
+	assert.Check(t, is.DeepEqual(sampleConfig.Networks, actual.Networks))
+	assert.Check(t, is.DeepEqual(sampleConfig.Volumes, actual.Volumes))
+}
+
 func TestLoadExtensions(t *testing.T) {
 	actual, err := loadYAML(`
 services: