diff --git a/devcontainer/devcontainer.go b/devcontainer/devcontainer.go
index 0bf7cc3..c57e490 100644
--- a/devcontainer/devcontainer.go
+++ b/devcontainer/devcontainer.go
@@ -204,7 +204,7 @@ func (s *Spec) Compile(fs billy.Filesystem, devcontainerDir, scratchDir string,
// We should make a best-effort attempt to find the user.
// Features must be executed as root, so we need to swap back
// to the running user afterwards.
- params.User, err = UserFromDockerfile(params.DockerfileContent)
+ params.User, err = UserFromDockerfile(params.DockerfileContent, buildArgs)
if err != nil {
return nil, fmt.Errorf("user from dockerfile: %w", err)
}
@@ -308,12 +308,57 @@ func (s *Spec) compileFeatures(fs billy.Filesystem, devcontainerDir, scratchDir
// UserFromDockerfile inspects the contents of a provided Dockerfile
// and returns the user that will be used to run the container.
-func UserFromDockerfile(dockerfileContent string) (user string, err error) {
+// Optionally accepts build args that may override default values in the Dockerfile.
+func UserFromDockerfile(dockerfileContent string, buildArgs ...[]string) (user string, err error) {
+ var args []string
+ if len(buildArgs) > 0 {
+ args = buildArgs[0]
+ }
+
res, err := parser.Parse(strings.NewReader(dockerfileContent))
if err != nil {
return "", fmt.Errorf("parse dockerfile: %w", err)
}
+ // Parse build args and ARG instructions to build the substitution context
+ lexer := shell.NewLex('\\')
+
+ // Start with build args provided externally (e.g., from devcontainer.json)
+ argsCopy := make([]string, len(args))
+ copy(argsCopy, args)
+
+ // Parse build args into a map for easy lookup
+ buildArgsMap := make(map[string]string)
+ for _, arg := range args {
+ if parts := strings.SplitN(arg, "=", 2); len(parts) == 2 {
+ buildArgsMap[parts[0]] = parts[1]
+ }
+ }
+
+ // Process ARG instructions to add default values if not overridden
+ lines := strings.Split(dockerfileContent, "\n")
+ for _, line := range lines {
+ if arg, ok := strings.CutPrefix(line, "ARG "); ok {
+ arg = strings.TrimSpace(arg)
+ if strings.Contains(arg, "=") {
+ parts := strings.SplitN(arg, "=", 2)
+ key, _, err := lexer.ProcessWord(parts[0], shell.EnvsFromSlice(argsCopy))
+ if err != nil {
+ return "", fmt.Errorf("processing %q: %w", line, err)
+ }
+
+ // Only use the default value if no build arg was provided
+ if _, exists := buildArgsMap[key]; !exists {
+ val, _, err := lexer.ProcessWord(parts[1], shell.EnvsFromSlice(argsCopy))
+ if err != nil {
+ return "", fmt.Errorf("processing %q: %w", line, err)
+ }
+ argsCopy = append(argsCopy, key+"="+val)
+ }
+ }
+ }
+ }
+
// Parse stages and user commands to determine the relevant user
// from the final stage.
var (
@@ -371,10 +416,16 @@ func UserFromDockerfile(dockerfileContent string) (user string, err error) {
}
// If we can't find a user command, try to find the user from
- // the image.
- ref, err := name.ParseReference(strings.TrimSpace(stage.BaseName))
+ // the image. First, substitute any ARG variables in the image name.
+ imageRef := stage.BaseName
+ imageRef, _, err := lexer.ProcessWord(imageRef, shell.EnvsFromSlice(argsCopy))
if err != nil {
- return "", fmt.Errorf("parse image ref %q: %w", stage.BaseName, err)
+ return "", fmt.Errorf("processing image ref %q: %w", stage.BaseName, err)
+ }
+
+ ref, err := name.ParseReference(strings.TrimSpace(imageRef))
+ if err != nil {
+ return "", fmt.Errorf("parse image ref %q: %w", imageRef, err)
}
user, err := UserFromImage(ref)
if err != nil {
@@ -388,27 +439,50 @@ func UserFromDockerfile(dockerfileContent string) (user string, err error) {
// ImageFromDockerfile inspects the contents of a provided Dockerfile
// and returns the image that will be used to run the container.
-func ImageFromDockerfile(dockerfileContent string) (name.Reference, error) {
- lexer := shell.NewLex('\\')
+// Optionally accepts build args that may override default values in the Dockerfile.
+func ImageFromDockerfile(dockerfileContent string, buildArgs ...[]string) (name.Reference, error) {
var args []string
+ if len(buildArgs) > 0 {
+ args = buildArgs[0]
+ }
+
+ lexer := shell.NewLex('\\')
+
+ // Start with build args provided externally (e.g., from devcontainer.json)
+ // These have higher precedence than default values in ARG instructions
+ argsCopy := make([]string, len(args))
+ copy(argsCopy, args)
+
+ // Parse build args into a map for easy lookup
+ buildArgsMap := make(map[string]string)
+ for _, arg := range args {
+ if parts := strings.SplitN(arg, "=", 2); len(parts) == 2 {
+ buildArgsMap[parts[0]] = parts[1]
+ }
+ }
+
var imageRef string
lines := strings.Split(dockerfileContent, "\n")
- // Iterate over lines in reverse
+ // Iterate over lines in reverse to find ARG declarations and FROM instruction
for i := len(lines) - 1; i >= 0; i-- {
line := lines[i]
if arg, ok := strings.CutPrefix(line, "ARG "); ok {
arg = strings.TrimSpace(arg)
if strings.Contains(arg, "=") {
parts := strings.SplitN(arg, "=", 2)
- key, _, err := lexer.ProcessWord(parts[0], shell.EnvsFromSlice(args))
+ key, _, err := lexer.ProcessWord(parts[0], shell.EnvsFromSlice(argsCopy))
if err != nil {
return nil, fmt.Errorf("processing %q: %w", line, err)
}
- val, _, err := lexer.ProcessWord(parts[1], shell.EnvsFromSlice(args))
- if err != nil {
- return nil, fmt.Errorf("processing %q: %w", line, err)
+
+ // Only use the default value if no build arg was provided
+ if _, exists := buildArgsMap[key]; !exists {
+ val, _, err := lexer.ProcessWord(parts[1], shell.EnvsFromSlice(argsCopy))
+ if err != nil {
+ return nil, fmt.Errorf("processing %q: %w", line, err)
+ }
+ argsCopy = append(argsCopy, key+"="+val)
}
- args = append(args, key+"="+val)
}
continue
}
@@ -421,7 +495,7 @@ func ImageFromDockerfile(dockerfileContent string) (name.Reference, error) {
if imageRef == "" {
return nil, fmt.Errorf("no FROM directive found")
}
- imageRef, _, err := lexer.ProcessWord(imageRef, shell.EnvsFromSlice(args))
+ imageRef, _, err := lexer.ProcessWord(imageRef, shell.EnvsFromSlice(argsCopy))
if err != nil {
return nil, fmt.Errorf("processing %q: %w", imageRef, err)
}
diff --git a/devcontainer/devcontainer_test.go b/devcontainer/devcontainer_test.go
index d304e76..650703c 100644
--- a/devcontainer/devcontainer_test.go
+++ b/devcontainer/devcontainer_test.go
@@ -204,6 +204,9 @@ func TestImageFromDockerfile(t *testing.T) {
}, {
content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:0-${VARIANT}",
image: "mcr.microsoft.com/devcontainers/python:0-3.10",
+ }, {
+ content: "ARG VARIANT=3-bookworm\nFROM mcr.microsoft.com/devcontainers/python:1-${VARIANT}",
+ image: "mcr.microsoft.com/devcontainers/python:1-3-bookworm",
}, {
content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:0-$VARIANT ",
image: "mcr.microsoft.com/devcontainers/python:0-3.10",
@@ -218,6 +221,120 @@ func TestImageFromDockerfile(t *testing.T) {
}
}
+func TestImageFromDockerfileWithArgs(t *testing.T) {
+ t.Parallel()
+ for _, tc := range []struct {
+ default_image string
+ content string
+ image string
+ }{{
+ default_image: "mcr.microsoft.com/devcontainers/python:1-3-bookworm",
+ content: "ARG VARIANT=3-bookworm\nFROM mcr.microsoft.com/devcontainers/python:1-${VARIANT}",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }, {
+ default_image: "mcr.microsoft.com/devcontainers/python:1-3.10",
+ content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:1-$VARIANT",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }, {
+ default_image: "mcr.microsoft.com/devcontainers/python:1-3.10",
+ content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:1-$VARIANT\nUSER app",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }} {
+ tc := tc
+ t.Run(tc.image, func(t *testing.T) {
+ t.Parallel()
+ dc := &devcontainer.Spec{
+ Build: devcontainer.BuildSpec{
+ Dockerfile: "Dockerfile",
+ Context: ".",
+ Args: map[string]string{
+ "VARIANT": "3.11-bookworm",
+ },
+ },
+ }
+ fs := memfs.New()
+ dcDir := "/workspaces/coder/.devcontainer"
+ err := fs.MkdirAll(dcDir, 0o755)
+ require.NoError(t, err)
+ file, err := fs.OpenFile(filepath.Join(dcDir, "Dockerfile"), os.O_CREATE|os.O_WRONLY, 0o644)
+ require.NoError(t, err)
+ _, err = io.WriteString(file, tc.content)
+ require.NoError(t, err)
+ _ = file.Close()
+ params, err := dc.Compile(fs, dcDir, workingDir, "", "/var/workspace", false, stubLookupEnv)
+ require.NoError(t, err)
+ require.Equal(t, "VARIANT=3.11-bookworm", params.BuildArgs[0])
+ require.Equal(t, params.DockerfileContent, tc.content)
+ ref, err := devcontainer.ImageFromDockerfile(tc.content, params.BuildArgs)
+ require.NoError(t, err)
+ require.Equal(t, tc.image, ref.Name())
+ // Test without args (using defaults)
+ fmt.Println("Testing ImageFromDockerfile without args...")
+ ref1, err := devcontainer.ImageFromDockerfile(tc.content)
+ require.NoError(t, err)
+ require.Equal(t, tc.default_image, ref1.Name())
+ })
+ }
+}
+
+func TestUserFromDockerfileWithArgs(t *testing.T) {
+ t.Parallel()
+ for _, tc := range []struct {
+ user string
+ content string
+ image string
+ }{{
+ user: "root",
+ content: "ARG VARIANT=3-bookworm\nFROM mcr.microsoft.com/devcontainers/python:1-${VARIANT}",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }, {
+ user: "root",
+ content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:1-$VARIANT",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }, {
+ user: "app",
+ content: "ARG VARIANT=\"3.10\"\nFROM mcr.microsoft.com/devcontainers/python:1-$VARIANT\nUSER app",
+ image: "mcr.microsoft.com/devcontainers/python:1-3.11-bookworm",
+ }} {
+ tc := tc
+ t.Run(tc.image, func(t *testing.T) {
+ t.Parallel()
+ dc := &devcontainer.Spec{
+ Build: devcontainer.BuildSpec{
+ Dockerfile: "Dockerfile",
+ Context: ".",
+ Args: map[string]string{
+ "VARIANT": "3.11-bookworm",
+ },
+ },
+ }
+ fs := memfs.New()
+ dcDir := "/workspaces/coder/.devcontainer"
+ err := fs.MkdirAll(dcDir, 0o755)
+ require.NoError(t, err)
+ file, err := fs.OpenFile(filepath.Join(dcDir, "Dockerfile"), os.O_CREATE|os.O_WRONLY, 0o644)
+ require.NoError(t, err)
+ _, err = io.WriteString(file, tc.content)
+ require.NoError(t, err)
+ _ = file.Close()
+ params, err := dc.Compile(fs, dcDir, workingDir, "", "/var/workspace", false, stubLookupEnv)
+ require.NoError(t, err)
+ require.Equal(t, "VARIANT=3.11-bookworm", params.BuildArgs[0])
+ require.Equal(t, params.DockerfileContent, tc.content)
+ // Test UserFromDockerfile without args
+ fmt.Println("\nTesting UserFromDockerfile without args...")
+ user1, err := devcontainer.UserFromDockerfile(tc.content)
+ require.NoError(t, err)
+ require.Equal(t, tc.user, user1)
+ // Test UserFromDockerfile with args
+ fmt.Println("\nTesting UserFromDockerfile with args...")
+ user2, err := devcontainer.UserFromDockerfile(tc.content, params.BuildArgs)
+ require.NoError(t, err)
+ require.Equal(t, tc.user, user2)
+ })
+ }
+}
+
func TestUserFrom(t *testing.T) {
t.Parallel()
diff --git a/envbuilder.go b/envbuilder.go
index ad2c84f..df90227 100644
--- a/envbuilder.go
+++ b/envbuilder.go
@@ -493,7 +493,7 @@ func run(ctx context.Context, opts options.Options, execArgs *execArgsInfo) erro
defer cleanupBuildContext()
if runtimeData.Built && opts.SkipRebuild {
endStage := startStage("🏗️ Skipping build because of cache...")
- imageRef, err := devcontainer.ImageFromDockerfile(buildParams.DockerfileContent)
+ imageRef, err := devcontainer.ImageFromDockerfile(buildParams.DockerfileContent, buildParams.BuildArgs)
if err != nil {
return nil, fmt.Errorf("image from dockerfile: %w", err)
}