fix: avoid hard fail when no config json file is present

[KatIsCoding]

Closes: #149

Problem

Callers of config.Load(), config.AuthConfigs, config.AuthConfigForHostname, and the context package helpers (Current, New, Delete, store.inspect) hard-fail when ~/.docker/config.json does not exist, even though the absence of a config file is a perfectly valid state on a fresh Docker installation.

Root Cause

config.Filepath() returns a generic fmt.Errorf("config file does not exist (%s)", configFilePath) when the file is missing. Load() wraps that into "config path: ..." and propagates it upward. Because every caller treats any non-nil error as fatal, a missing config file tears down operations that should legitimately proceed with empty/default auth or the default context.

Fix

Introduce a sentinel error, config.ErrConfigFileNotFound, joined into the error returned by Filepath() via errors.Join, so callers can distinguish "no config file" from real I/O or parse failures using errors.Is.

• config/auth.go: AuthConfigs and AuthConfigForHostname return an empty auth config when the file is missing, instead of erroring.
• context/current.go: Current() falls back to DefaultContextName (mirroring the existing os.IsNotExist branch for the meta file).
• context/context.add.go, context/context.delete.go, context/store.go: the "set current" / "reset current" / inspect paths treat a missing config file as a no-op rather than failing.
• config/load.go: Load() also tolerates os.ErrNotExist from loadFromFilepath (race between Filepath() and the read) by returning an empty Config.

Testing

• No new tests added in this change. Existing config and context suites continue to pass.

[mdelapenya]

LGTM, although I added a suggestion about the location of the new sentinel error. Also, could you unit test the new code paths?

Thanks for working on the fix!

[mdelapenya]

suggestion: could you locate this sentinel error in an errors.go file? Other packages/modules already do that. Also, the comment for the next function has been moved.

[Copilot]

Pull request overview

This PR aims to make the SDK tolerant of missing Docker CLI config (~/.docker/config.json) by introducing a sentinel error and updating config/auth/context helpers to treat “no config file” as a valid empty/default state instead of a fatal error.

Changes:

• Add config.ErrConfigFileNotFound and include it in Filepath() errors to enable errors.Is-based handling.
• Update auth helpers (AuthConfigs, AuthConfigForHostname) and context helpers (Current, New, Delete, store.inspect) to special-case the sentinel and avoid hard failures.
• Make Load() tolerate os.ErrNotExist from the read path (race between existence check and open).

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
config/load.go	Introduces ErrConfigFileNotFound, joins it into Filepath() errors, and relaxes Load() for os.ErrNotExist.
config/auth.go	Special-cases missing config file in auth entrypoints.
context/current.go	Falls back to DefaultContextName when Docker config is missing.
context/context.add.go	Treats missing config as a no-op when attempting to set the newly created context as current.
context/context.delete.go	Treats missing config as a no-op when attempting to reset current context on delete.
context/store.go	Treats missing config as a no-op during inspect (but currently skips required context field initialization).

Comments suppressed due to low confidence (1)

config/load.go:84

• Even with ErrConfigFileNotFound, a very common "fresh install" state is that the directory (~/.docker / DOCKER_CONFIG) is missing. Dir() currently errors when the directory is absent, and that error does not include ErrConfigFileNotFound, so callers checking errors.Is(err, ErrConfigFileNotFound) will still hard-fail. To fully address the reported scenario, the missing-directory case needs to surface the same sentinel (or otherwise become distinguishable from real I/O/permission errors).

func Filepath() (string, error) {
	dir, err := Dir()
	if err != nil {
		return "", fmt.Errorf("config dir: %w", err)
	}

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[KatIsCoding]

@mdelapenya Thanks for your review! I implemented your suggestion, as well as some of the suggestions that copilot gave and the unit tests for the no config scenario!

[Copilot]

Pull request overview

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.