feat(context): create and delete docker contexts (#80)

* chore: check the current docker socket path has a valid schema

* feat: check for rootless docker using the XDG_RUNTIME_DIR env var

* feat(config): save a config file to disk

* feat: add and delete docker contexts

* chore: set default context if the deleted one is the current

* docs: document new APIs

* fix: proper rootless env var check

* chore: proper variable name

* chore: rename error message

* fix: proper order in go.work

* chore: proper error message

* chore: store config filepath in the struct

* docs: document saving the config

* chore: simplify

Author: mdelapenya

config/README.md

@@ -16,7 +16,7 @@ go get github.com/docker/go-sdk/config
 
 #### Directory
 
-It will return the current Docker config directory.
+It returns the current Docker config directory.
 
 ```go
 dir, err := config.Dir()
@@ -29,7 +29,7 @@ fmt.Printf("current docker config directory: %s", dir)
 
 #### Filepath
 
-It will return the path to the Docker config file.
+It returns the path to the Docker config file.
 
 ```go
 filepath, err := config.Filepath()
@@ -42,7 +42,7 @@ fmt.Printf("current docker config file path: %s", filepath)
 
 #### Load
 
-It will return the Docker config.
+It returns the Docker config.
 
 ```go
 cfg, err := config.Load()
@@ -53,11 +53,21 @@ if err != nil {
 fmt.Printf("docker config: %+v", cfg)
 ```
 
+#### Save
+
+Once you have loaded a config, you can save it back to the file system.
+
+```go
+if err := cfg.Save(); err != nil {
+    log.Fatalf("failed to save docker config: %v", err)
+}
+```
+
 ### Auth
 
 #### AuthConfigs
 
-It will return a maps of the registry credentials for the given Docker images, indexed by the registry hostname.
+It returns a maps of the registry credentials for the given Docker images, indexed by the registry hostname.
 
 ```go
 authConfigs, err := config.AuthConfigs("nginx:latest")
@@ -70,7 +80,7 @@ fmt.Printf("registry credentials: %+v", authConfigs)
 
 #### Auth Configs For Hostname
 
-It will return the registry credentials for the given Docker registry.
+It returns the registry credentials for the given Docker registry.
 
 ```go
 authConfig, err := config.AuthConfigForHostname("https://index.docker.io/v1/")

config/auth_test.go

@@ -87,7 +87,11 @@ func validateAuthForHostname(t *testing.T, hostname, expectedUser, expectedPass
 	t.Helper()
 
 	creds, err := AuthConfigForHostname(hostname)
-	require.ErrorIs(t, err, expectedErr)
+	if expectedErr != nil {
+		require.ErrorContains(t, err, expectedErr.Error())
+	} else {
+		require.NoError(t, err)
+	}
 	require.Equal(t, expectedUser, creds.Username)
 	require.Equal(t, expectedPass, creds.Password)
 	if creds.ServerAddress != "" {
@@ -100,7 +104,11 @@ func validateAuthForImage(t *testing.T, imageRef, expectedUser, expectedPass, ex
 	t.Helper()
 
 	authConfigs, err := AuthConfigs(imageRef)
-	require.ErrorIs(t, err, expectedErr)
+	if expectedErr != nil {
+		require.ErrorContains(t, err, expectedErr.Error())
+	} else {
+		require.NoError(t, err)
+	}
 
 	creds, ok := authConfigs[expectedRegistry]
 	require.Equal(t, (expectedErr == nil), ok)
@@ -194,7 +202,7 @@ func TestRegistryCredentialsForImage(t *testing.T) {
 
 	t.Run("config/not-found", func(t *testing.T) {
 		t.Setenv(EnvOverrideDir, filepath.Join("testdata", "missing"))
-		validateAuthForImage(t, "userpass.io/repo/image:tag", "", "", "", os.ErrNotExist)
+		validateAuthForImage(t, "userpass.io/repo/image:tag", "", "", "", errors.New("file does not exist"))
 	})
 }
 
@@ -258,7 +266,7 @@ func TestRegistryCredentialsForHostname(t *testing.T) {
 
 	t.Run("config/not-found", func(t *testing.T) {
 		t.Setenv(EnvOverrideDir, filepath.Join("testdata", "missing"))
-		validateAuthForHostname(t, "userpass.io", "", "", os.ErrNotExist)
+		validateAuthForHostname(t, "userpass.io", "", "", errors.New("file does not exist"))
 	})
 }
 

config/config.go

@@ -7,6 +7,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"os"
 	"strings"
 	"sync"
 	"time"
@@ -194,6 +195,16 @@ func (c *Config) ParseProxyConfig(host string, runOpts map[string]*string) map[s
 	return m
 }
 
+// Save saves the config to the file system
+func (c *Config) Save() error {
+	data, err := json.Marshal(c)
+	if err != nil {
+		return fmt.Errorf("json marshal: %w", err)
+	}
+
+	return os.WriteFile(c.filepath, data, 0o644)
+}
+
 // resolveAuthConfigForHostname performs the actual auth config resolution
 func (c *Config) resolveAuthConfigForHostname(hostname string) (AuthConfig, error) {
 	// Check credential helpers first

config/config_test.go

@@ -1,6 +1,8 @@
 package config
 
 import (
+	"os"
+	"path/filepath"
 	"sync"
 	"testing"
 
@@ -101,3 +103,29 @@ func TestConfig_CacheKeyGeneration(t *testing.T) {
 
 	require.NotEqual(t, stats1.CacheKey, stats2.CacheKey)
 }
+
+func TestConfigSave(t *testing.T) {
+	tmpDir := t.TempDir()
+	setupHome(t, tmpDir)
+
+	dockerDir := filepath.Join(tmpDir, ".docker")
+
+	err := os.MkdirAll(dockerDir, 0o755)
+	require.NoError(t, err)
+
+	_, err = os.Create(filepath.Join(dockerDir, FileName))
+	require.NoError(t, err)
+
+	c := Config{
+		filepath:       filepath.Join(dockerDir, FileName),
+		CurrentContext: "test",
+		AuthConfigs:    map[string]AuthConfig{},
+	}
+
+	require.NoError(t, c.Save())
+
+	cfg, err := Load()
+	require.NoError(t, err)
+	require.Equal(t, c.CurrentContext, cfg.CurrentContext)
+	require.Equal(t, c.AuthConfigs, cfg.AuthConfigs)
+}

config/load.go

@@ -46,8 +46,8 @@ func getHomeDir() (string, error) {
 func Dir() (string, error) {
 	dir := os.Getenv(EnvOverrideDir)
 	if dir != "" {
-		if err := fileExists(dir); err != nil {
-			return "", fmt.Errorf("file exists: %w", err)
+		if !fileExists(dir) {
+			return "", fmt.Errorf("file does not exist (%s)", dir)
 		}
 		return dir, nil
 	}
@@ -58,19 +58,19 @@ func Dir() (string, error) {
 	}
 
 	configDir := filepath.Join(home, configFileDir)
-	if err := fileExists(configDir); err != nil {
-		return "", fmt.Errorf("file exists: %w", err)
+	if !fileExists(configDir) {
+		return "", fmt.Errorf("file does not exist (%s)", configDir)
 	}
 
 	return configDir, nil
 }
 
-func fileExists(path string) error {
+func fileExists(path string) bool {
 	if _, err := os.Stat(path); os.IsNotExist(err) {
-		return fmt.Errorf("file does not exist: %w", err)
+		return false
 	}
 
-	return nil
+	return true
 }
 
 // Filepath returns the path to the docker cli config file,
@@ -82,8 +82,8 @@ func Filepath() (string, error) {
 	}
 
 	configFilePath := filepath.Join(dir, FileName)
-	if err := fileExists(configFilePath); err != nil {
-		return "", fmt.Errorf("config file: %w", err)
+	if !fileExists(configFilePath) {
+		return "", fmt.Errorf("config file does not exist (%s)", configFilePath)
 	}
 
 	return configFilePath, nil
@@ -113,6 +113,9 @@ func Load() (Config, error) {
 		return cfg, fmt.Errorf("load config: %w", err)
 	}
 
+	// store the location of the config file into the config, for future use
+	cfg.filepath = p
+
 	return cfg, nil
 }
 

config/load_test.go

@@ -14,14 +14,16 @@ import (
 var dockerConfig string
 
 func TestLoad(t *testing.T) {
-	var expectedConfig Config
-	err := json.Unmarshal([]byte(dockerConfig), &expectedConfig)
-	require.NoError(t, err)
-
 	t.Run("HOME", func(t *testing.T) {
 		t.Run("valid", func(t *testing.T) {
 			setupHome(t, "testdata")
 
+			var expectedConfig Config
+			err := json.Unmarshal([]byte(dockerConfig), &expectedConfig)
+			require.NoError(t, err)
+
+			expectedConfig.filepath = filepath.Join("testdata", ".docker", FileName)
+
 			cfg, err := Load()
 			require.NoError(t, err)
 			require.Equal(t, expectedConfig, cfg)
@@ -31,7 +33,7 @@ func TestLoad(t *testing.T) {
 			setupHome(t, "testdata", "not-found")
 
 			cfg, err := Load()
-			require.ErrorIs(t, err, os.ErrNotExist)
+			require.ErrorContains(t, err, "file does not exist")
 			require.Empty(t, cfg)
 		})
 
@@ -49,6 +51,10 @@ func TestLoad(t *testing.T) {
 			setupHome(t, "testdata", "not-found")
 			t.Setenv("DOCKER_AUTH_CONFIG", dockerConfig)
 
+			var expectedConfig Config
+			err := json.Unmarshal([]byte(dockerConfig), &expectedConfig)
+			require.NoError(t, err)
+
 			cfg, err := Load()
 			require.NoError(t, err)
 			require.Equal(t, expectedConfig, cfg)
@@ -69,6 +75,12 @@ func TestLoad(t *testing.T) {
 			setupHome(t, "testdata", "not-found")
 			t.Setenv(EnvOverrideDir, filepath.Join("testdata", ".docker"))
 
+			var expectedConfig Config
+			err := json.Unmarshal([]byte(dockerConfig), &expectedConfig)
+			require.NoError(t, err)
+
+			expectedConfig.filepath = filepath.Join("testdata", ".docker", FileName)
+
 			cfg, err := Load()
 			require.NoError(t, err)
 			require.Equal(t, expectedConfig, cfg)
@@ -105,7 +117,7 @@ func TestDir(t *testing.T) {
 			setupHome(t, "testdata", "not-found")
 
 			dir, err := Dir()
-			require.ErrorIs(t, err, os.ErrNotExist)
+			require.ErrorContains(t, err, "file does not exist")
 			require.Empty(t, dir)
 		})
 	})
@@ -124,7 +136,7 @@ func TestDir(t *testing.T) {
 			setupDockerConfigs(t, "testdata", "not-found")
 
 			dir, err := Dir()
-			require.ErrorIs(t, err, os.ErrNotExist)
+			require.ErrorContains(t, err, "file does not exist")
 			require.Empty(t, dir)
 		})
 	})

config/types.go

@@ -19,6 +19,7 @@ const (
 
 // Config represents the on disk format of the docker CLI's config file.
 type Config struct {
+	filepath             string                 `json:"-"`
 	AuthConfigs          map[string]AuthConfig  `json:"auths"`
 	HTTPHeaders          map[string]string      `json:"HttpHeaders,omitempty"`
 	PsFormat             string                 `json:"psFormat,omitempty"`

context/README.md

@@ -77,4 +77,47 @@ if err != nil {
 }
 
 fmt.Printf("contexts: %v", contexts)
+```
+
+### Add Context
+
+It adds a new context to the Docker configuration, identified by a name. It's possible to pass options to customize the context definition.
+
+```go
+ctx, err := context.New("my-context")
+if err != nil {
+    log.Printf("failed to add context: %v", err)
+    return
+}
+
+fmt.Printf("context added: %s", ctx.Name)
+```
+
+### Available Options
+
+The following options are available to customize the context definition:
+
+- `WithHost(host string) CreateContextOption` sets the host for the context.
+- `WithDescription(description string) CreateContextOption` sets the description for the context.
+- `WithAdditionalFields(fields map[string]any) CreateContextOption` sets the additional fields for the context.
+- `WithSkipTLSVerify() CreateContextOption` sets the skipTLSVerify flag to true.
+- `AsCurrent() CreateContextOption` sets the context as the current context, saving the current context to the Docker configuration.
+
+### Delete Context
+
+It deletes a context from the Docker configuration.
+
+```go
+ctx, err := context.New("my-context")
+if err != nil {
+    log.Printf("error adding context: %s", err)
+    return
+}
+
+if err := ctx.Delete(); err != nil {
+    log.Printf("failed to delete context: %v", err)
+    return
+}
+
+fmt.Printf("context deleted: %s", ctx.Name)
 ```