bake: load .env file from working dir for compose files

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

bake/bake.go

@@ -179,6 +179,21 @@ func dedupMap(ms ...map[string]string) map[string]string {
 	return res
 }
 
+func sliceToMap(env []string) (res map[string]string) {
+	res = make(map[string]string)
+	for _, s := range env {
+		kv := strings.SplitN(s, "=", 2)
+		key := kv[0]
+		switch {
+		case len(kv) == 1:
+			res[key] = ""
+		default:
+			res[key] = kv[1]
+		}
+	}
+	return
+}
+
 func ParseFiles(files []File, defaults map[string]string) (_ *Config, err error) {
 	defer func() {
 		err = formatHCLError(err, files)
@@ -242,15 +257,22 @@ func ParseFile(dt []byte, fn string) (*Config, error) {
 }
 
 func ParseComposeFile(dt []byte, fn string) (*Config, bool, error) {
+	envs := sliceToMap(os.Environ())
+	if wd, err := os.Getwd(); err == nil {
+		envs, err = loadDotEnv(envs, wd)
+		if err != nil {
+			return nil, true, err
+		}
+	}
 	fnl := strings.ToLower(fn)
 	if strings.HasSuffix(fnl, ".yml") || strings.HasSuffix(fnl, ".yaml") {
-		cfg, err := ParseCompose(dt)
+		cfg, err := ParseCompose(dt, envs)
 		return cfg, true, err
 	}
 	if strings.HasSuffix(fnl, ".json") || strings.HasSuffix(fnl, ".hcl") {
 		return nil, false, nil
 	}
-	cfg, err := ParseCompose(dt)
+	cfg, err := ParseCompose(dt, envs)
 	return cfg, err == nil, err
 }
 

bake/compose.go

@@ -3,8 +3,10 @@ package bake
 import (
 	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
+	"github.com/compose-spec/compose-go/dotenv"
 	"github.com/compose-spec/compose-go/loader"
 	compose "github.com/compose-spec/compose-go/types"
 	"github.com/pkg/errors"
@@ -14,34 +16,18 @@ import (
 // errComposeInvalid is returned when a compose file is invalid
 var errComposeInvalid = errors.New("invalid compose file")
 
-func parseCompose(dt []byte) (*compose.Project, error) {
+func ParseCompose(dt []byte, envs map[string]string) (*Config, error) {
-	return loader.Load(compose.ConfigDetails{
+	cfg, err := loader.Load(compose.ConfigDetails{
 		ConfigFiles: []compose.ConfigFile{
 			{
 				Content: dt,
 			},
 		},
-		Environment: envMap(os.Environ()),
+		Environment: envs,
 	}, func(options *loader.Options) {
 		options.SkipNormalization = true
 		options.SkipConsistencyCheck = true
 	})
-}
-
-func envMap(env []string) map[string]string {
-	result := make(map[string]string, len(env))
-	for _, s := range env {
-		kv := strings.SplitN(s, "=", 2)
-		if len(kv) != 2 {
-			continue
-		}
-		result[kv[0]] = kv[1]
-	}
-	return result
-}
-
-func ParseCompose(dt []byte) (*Config, error) {
-	cfg, err := parseCompose(dt)
 	if err != nil {
 		return nil, err
 	}
@@ -124,6 +110,42 @@ func ParseCompose(dt []byte) (*Config, error) {
 	return &c, nil
 }
 
+func loadDotEnv(curenv map[string]string, workingDir string) (map[string]string, error) {
+	if curenv == nil {
+		curenv = make(map[string]string)
+	}
+
+	ef, err := filepath.Abs(filepath.Join(workingDir, ".env"))
+	if err != nil {
+		return nil, err
+	}
+
+	if _, err = os.Stat(ef); os.IsNotExist(err) {
+		return curenv, nil
+	} else if err != nil {
+		return nil, err
+	}
+
+	dt, err := os.ReadFile(ef)
+	if err != nil {
+		return nil, err
+	}
+
+	envs, err := dotenv.UnmarshalBytes(dt)
+	if err != nil {
+		return nil, err
+	}
+
+	for k, v := range envs {
+		if _, set := curenv[k]; set {
+			continue
+		}
+		curenv[k] = v
+	}
+
+	return curenv, nil
+}
+
 func flatten(in compose.MappingWithEquals) compose.Mapping {
 	if len(in) == 0 {
 		return nil

bake/compose_test.go

@@ -2,6 +2,7 @@ package bake
 
 import (
 	"os"
+	"path/filepath"
 	"sort"
 	"testing"
 
@@ -37,7 +38,7 @@ secrets:
     file: /root/.aws/credentials
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 
 	require.Equal(t, 1, len(c.Groups))
@@ -75,7 +76,7 @@ services:
     webapp:
         build: ./db
 `)
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, 1, len(c.Groups))
 }
@@ -93,7 +94,7 @@ services:
       target: webapp
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 
 	require.Equal(t, 2, len(c.Targets))
@@ -118,7 +119,7 @@ services:
       target: webapp
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, 2, len(c.Targets))
 	sort.Slice(c.Targets, func(i, j int) bool {
@@ -152,7 +153,7 @@ services:
 	os.Setenv("ZZZ_BAR", "zzz_foo")
 	defer os.Unsetenv("ZZZ_BAR")
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, sliceToMap(os.Environ()))
 	require.NoError(t, err)
 	require.Equal(t, "bar", c.Targets[0].Args["FOO"])
 	require.Equal(t, "zzz_foo", c.Targets[0].Args["BAR"])
@@ -166,7 +167,7 @@ services:
     entrypoint: echo 1
 `)
 
-	_, err := ParseCompose(dt)
+	_, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 }
 
@@ -191,7 +192,7 @@ networks:
           gateway: 10.5.0.254
 `)
 
-	_, err := ParseCompose(dt)
+	_, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 }
 
@@ -208,7 +209,7 @@ services:
         - bar
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, []string{"foo", "bar"}, c.Targets[0].Tags)
 }
@@ -245,7 +246,7 @@ networks:
     name: test-net
 `)
 
-	_, err := ParseCompose(dt)
+	_, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 }
 
@@ -298,7 +299,7 @@ services:
         no-cache: true
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, 2, len(c.Targets))
 	sort.Slice(c.Targets, func(i, j int) bool {
@@ -342,7 +343,7 @@ services:
           - type=local,dest=path/to/cache
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, 1, len(c.Targets))
 	require.Equal(t, []string{"ct-addon:foo", "ct-addon:baz"}, c.Targets[0].Tags)
@@ -375,11 +376,32 @@ services:
       - ` + envf.Name() + `
 `)
 
-	c, err := ParseCompose(dt)
+	c, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 	require.Equal(t, map[string]string{"CT_ECR": "foo", "FOO": "bsdf -csdf", "NODE_ENV": "test"}, c.Targets[0].Args)
 }
 
+func TestDotEnv(t *testing.T) {
+	tmpdir := t.TempDir()
+
+	err := os.WriteFile(filepath.Join(tmpdir, ".env"), []byte("FOO=bar"), 0644)
+	require.NoError(t, err)
+
+	var dt = []byte(`
+services:
+  scratch:
+    build:
+     context: .
+     args:
+        FOO:
+`)
+
+	chdir(t, tmpdir)
+	c, _, err := ParseComposeFile(dt, "docker-compose.yml")
+	require.NoError(t, err)
+	require.Equal(t, map[string]string{"FOO": "bar"}, c.Targets[0].Args)
+}
+
 func TestPorts(t *testing.T) {
 	var dt = []byte(`
 services:
@@ -397,7 +419,7 @@ services:
         published: "3306"
         protocol: tcp
 `)
-	_, err := ParseCompose(dt)
+	_, err := ParseCompose(dt, nil)
 	require.NoError(t, err)
 }
 
@@ -445,10 +467,10 @@ func TestServiceName(t *testing.T) {
 		t.Run(tt.svc, func(t *testing.T) {
 			_, err := ParseCompose([]byte(`
 services:
-  ` + tt.svc + `:
+  `+tt.svc+`:
     build:
       context: .
-`))
+`), nil)
 			if tt.wantErr {
 				require.Error(t, err)
 			} else {
@@ -514,7 +536,7 @@ services:
 	for _, tt := range cases {
 		tt := tt
 		t.Run(tt.name, func(t *testing.T) {
-			_, err := ParseCompose(tt.dt)
+			_, err := ParseCompose(tt.dt, nil)
 			if tt.wantErr {
 				require.Error(t, err)
 			} else {
@@ -523,3 +545,21 @@ services:
 		})
 	}
 }
+
+// chdir changes the current working directory to the named directory,
+// and then restore the original working directory at the end of the test.
+func chdir(t *testing.T, dir string) {
+	olddir, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("chdir: %v", err)
+	}
+	if err := os.Chdir(dir); err != nil {
+		t.Fatalf("chdir %s: %v", dir, err)
+	}
+	t.Cleanup(func() {
+		if err := os.Chdir(olddir); err != nil {
+			t.Errorf("chdir to original working directory %s: %v", olddir, err)
+			os.Exit(1)
+		}
+	})
+}

docs/guides/bake/compose-file.md

@@ -94,6 +94,56 @@ limitations with the compose format:
 * Specifying variables or global scope attributes is not yet supported
 * `inherits` service field is not supported, but you can use [YAML anchors](https://docs.docker.com/compose/compose-file/#fragments) to reference other services like the example above
 
+## `.env` file
+
+You can declare default environment variables in an environment file named
+`.env`. This file will be loaded from the current working directory,
+where the command is executed and applied to compose definitions passed
+with `-f`.
+
+```yaml
+# docker-compose.yml
+services:
+  webapp:
+    image: docker.io/username/webapp:${TAG:-v1.0.0}
+    build:
+      dockerfile: Dockerfile
+```
+
+```
+# .env
+TAG=v1.1.0
+```
+
+```console
+$ docker buildx bake --print
+```
+```json
+{
+  "group": {
+    "default": {
+      "targets": [
+        "webapp"
+      ]
+    }
+  },
+  "target": {
+    "webapp": {
+      "context": ".",
+      "dockerfile": "Dockerfile",
+      "tags": [
+        "docker.io/username/webapp:v1.1.0"
+      ]
+    }
+  }
+}
+```
+
+> **Note**
+>
+> System environment variables take precedence over environment variables
+> in `.env` file.
+
 ## Extension field with `x-bake`
 
 Even if some fields are not (yet) available in the compose specification, you