Add IsAuthenticated

Fixes cli#32. Also exports error types.

gh.go

@@ -7,7 +7,6 @@ package gh
 
 import (
 	"bytes"
-	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -20,6 +19,7 @@ import (
 	irepo "github.com/cli/go-gh/internal/repository"
 	"github.com/cli/go-gh/internal/ssh"
 	"github.com/cli/go-gh/pkg/api"
+	gherrors "github.com/cli/go-gh/pkg/errors"
 	repo "github.com/cli/go-gh/pkg/repository"
 	"github.com/cli/safeexec"
 )
@@ -125,7 +125,7 @@ func CurrentRepository() (repo.Repository, error) {
 		return nil, err
 	}
 	if len(remotes) == 0 {
-		return nil, errors.New("unable to determine current repository, no git remotes configured for this repository")
+		return nil, gherrors.ErrNoRepositories
 	}
 
 	sshConfig := ssh.ParseConfig()
@@ -140,13 +140,29 @@ func CurrentRepository() (repo.Repository, error) {
 
 	filteredRemotes := remotes.FilterByHosts(hosts)
 	if len(filteredRemotes) == 0 {
-		return nil, errors.New("unable to determine current repository, none of the git remotes configured for this repository point to a known GitHub host")
+		return nil, gherrors.ErrNoRepositoryHosts
 	}
 
 	r := filteredRemotes[0]
 	return irepo.New(r.Host, r.Owner, r.Repo), nil
 }
 
+// IsAuthenticated returns whether the user has authenticated the given host.
+// The default host "github.com" is used if host is "".
+func IsAuthenticated(host string) bool {
+	cfg, err := config.Load()
+	if err != nil {
+		return false
+	}
+
+	if host == "" {
+		host = cfg.Host()
+	}
+
+	_, err = cfg.AuthToken(host)
+	return err == nil
+}
+
 func resolveOptions(opts *api.ClientOptions, cfg config.Config) error {
 	var token string
 	var err error

internal/config/config.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 
 	"github.com/cli/go-gh/internal/set"
+	gherrors "github.com/cli/go-gh/pkg/errors"
 	"gopkg.in/yaml.v3"
 )
 
@@ -89,7 +90,7 @@ func (c config) AuthToken(host string) (string, error) {
 		if token, err := c.GetForHost(hostname, oauthToken); err == nil {
 			return token, nil
 		}
-		return "", NotFoundError{errors.New("not found")}
+		return "", gherrors.ErrNotFound
 	}
 
 	if token := os.Getenv(ghToken); token != "" {
@@ -101,7 +102,7 @@ func (c config) AuthToken(host string) (string, error) {
 	if token, err := c.GetForHost(hostname, oauthToken); err == nil {
 		return token, nil
 	}
-	return "", NotFoundError{errors.New("not found")}
+	return "", gherrors.ErrNotFound
 }
 
 func isEnterprise(host string) bool {

internal/config/config_map.go

@@ -3,6 +3,7 @@ package config
 import (
 	"errors"
 
+	gherrors "github.com/cli/go-gh/pkg/errors"
 	"gopkg.in/yaml.v3"
 )
 
@@ -19,10 +20,6 @@ type configEntry struct {
 	Index     int
 }
 
-type NotFoundError struct {
-	error
-}
-
 func (cm *configMap) empty() bool {
 	return cm.Root == nil || len(cm.Root.Content) == 0
 }
@@ -42,7 +39,7 @@ func (cm *configMap) setStringValue(key, value string) error {
 		return nil
 	}
 
-	var notFound *NotFoundError
+	var notFound *gherrors.NotFoundError
 	if err != nil && !errors.As(err, &notFound) {
 		return err
 	}
@@ -63,7 +60,7 @@ func (cm *configMap) setStringValue(key, value string) error {
 
 func (cm *configMap) findEntry(key string) (*configEntry, error) {
 	if cm.empty() {
-		return nil, &NotFoundError{errors.New("not found")}
+		return nil, &gherrors.ErrNotFound
 	}
 
 	ce := &configEntry{}
@@ -85,7 +82,7 @@ func (cm *configMap) findEntry(key string) (*configEntry, error) {
 		}
 	}
 
-	return nil, &NotFoundError{errors.New("not found")}
+	return nil, &gherrors.ErrNotFound
 }
 
 func (cm *configMap) removeEntry(key string) {

pkg/errors/errors.go

@@ -0,0 +1,26 @@
+package errors
+
+import "errors"
+
+// NoRepositoriesError is returned when go-gh is unable to determine current repository,
+// when no git remotes configured for this repository.
+type NoRepositoriesError struct {
+	error
+}
+
+// NoRepositoryHostsError is returned when go-gh is unable to determine current repository,
+// when none of the git remotes configured for this repository point to a known GitHub host.
+type NoRepositoryHostsError struct {
+	error
+}
+
+// NotFoundError is returned when there is no authentication token for the host.
+type NotFoundError struct {
+	error
+}
+
+var (
+	ErrNoRepositories    = NoRepositoriesError{errors.New("unable to determine current repository, no git remotes configured for this repository")}
+	ErrNoRepositoryHosts = NoRepositoryHostsError{errors.New("unable to determine current repository, none of the git remotes configured for this repository point to a known GitHub host")}
+	ErrNotFound          = NotFoundError{errors.New("not found")}
+)