fix: Use DOCKER_CONFIG env same way as with docker cli (#849)

Author: Junkern

.github/workflows/acc-test.yaml

@@ -25,7 +25,6 @@ jobs:
       fail-fast: false
       matrix:
         terraform_version:
-        - "0.15.x"
         - "1.8.x"
         resource_type:
         - "TestAccDockerConfig"

docs/index.md

@@ -172,7 +172,7 @@ Required:
 Optional:
 
 - `auth_disabled` (Boolean) Setting this to `true` will tell the provider that this registry does not need authentication. Due to the docker internals, the provider will use dummy credentials (see https://github.com/kreuzwerker/terraform-provider-docker/issues/470 for more information). Defaults to `false`.
-- `config_file` (String) Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` is set, the value of `DOCKER_CONFIG` is used as the path. `config_file` has predencen over all other options.
+- `config_file` (String) Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` env variable is set, the value of `DOCKER_CONFIG` is used as the path. `DOCKER_CONFIG` can be set to a directory (as per Docker CLI) or a file path directly. `config_file` has precedence over all other options.
 - `config_file_content` (String) Plain content of the docker json file for registry auth. `config_file_content` has precedence over username/password.
 - `password` (String, Sensitive) Password for the registry. Defaults to `DOCKER_REGISTRY_PASS` env variable if set.
 - `username` (String) Username for the registry. Defaults to `DOCKER_REGISTRY_USER` env variable if set.

internal/provider/framework_provider.go

@@ -96,7 +96,7 @@ func (p *frameworkProvider) Schema(ctx context.Context, req provider.SchemaReque
 							Sensitive:           true,
 						},
 						"config_file": schema.StringAttribute{
-							MarkdownDescription: "Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` is set, the value of `DOCKER_CONFIG` is used as the path. `config_file` has predencen over all other options.",
+							MarkdownDescription: "Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` env variable is set, the value of `DOCKER_CONFIG` is used as the path. `DOCKER_CONFIG` can be set to a directory (as per Docker CLI) or a file path directly. `config_file` has precedence over all other options.",
 							Optional:            true,
 						},
 						"config_file_content": schema.StringAttribute{

internal/provider/provider.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"os"
 	"os/user"
+	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
@@ -128,12 +129,23 @@ func New(version string) func() *schema.Provider {
 							},
 
 							"config_file": {
-								Type:        schema.TypeString,
-								Optional:    true,
-								DefaultFunc: schema.EnvDefaultFunc("DOCKER_CONFIG", "~/.docker/config.json"),
-								Description: "Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` is set, the value of `DOCKER_CONFIG` is used as the path. `config_file` has predencen over all other options.",
+								Type:     schema.TypeString,
+								Optional: true,
+								DefaultFunc: func() (interface{}, error) {
+									if v := os.Getenv("DOCKER_CONFIG"); v != "" {
+										// Docker CLI expects DOCKER_CONFIG to be a directory containing config.json
+										// Check if it's a directory and append config.json if needed
+										info, err := os.Stat(v)
+										if err == nil && info.IsDir() {
+											return filepath.Join(v, "config.json"), nil
+										}
+										// If it's a file or doesn't exist, use it as-is for backwards compatibility
+										return v, nil
+									}
+									return "~/.docker/config.json", nil
+								},
+								Description: "Path to docker json file for registry auth. Defaults to `~/.docker/config.json`. If `DOCKER_CONFIG` env variable is set, the value of `DOCKER_CONFIG` is used as the path. `DOCKER_CONFIG` can be set to a directory (as per Docker CLI) or a file path directly. `config_file` has precedence over all other options.",
 							},
-
 							"config_file_content": {
 								Type:        schema.TypeString,
 								Optional:    true,