Always resolve .databrickscfg file (#659)

## Changes
#629 introduced a change to autopopulate the host from .databrickscfg if
the user is logging back into a host they were previously using. This
did not respect the DATABRICKS_CONFIG_FILE env variable, causing the
flow to stop working for users with no .databrickscfg file in their home
directory.

This PR refactors all config file loading to go through one interface,
`databrickscfg.GetDatabricksCfg()`, and an auxiliary
`databrickscfg.GetDatabricksCfgPath()` to get the configured file path.

Closes #655.

## Tests
```
$ databricks auth login --profile abc
Error: open /Users/miles/.databrickscfg: no such file or directory

$ ./cli auth login --profile abc
Error: cannot load Databricks config file: open /Users/miles/.databrickscfg: no such file or directory


$ DATABRICKS_CONFIG_FILE=~/.databrickscfg.bak ./cli auth login --profile abc
Databricks Host: https://asdf
```

cmd/auth/env.go

@@ -9,6 +9,7 @@ import (
 	"net/url"
 	"strings"
 
+	"github.com/databricks/cli/libs/databrickscfg"
 	"github.com/databricks/databricks-sdk-go/config"
 	"github.com/spf13/cobra"
 	"gopkg.in/ini.v1"
@@ -28,7 +29,7 @@ func canonicalHost(host string) (string, error) {
 
 var ErrNoMatchingProfiles = errors.New("no matching profiles found")
 
-func resolveSection(cfg *config.Config, iniFile *ini.File) (*ini.Section, error) {
+func resolveSection(cfg *config.Config, iniFile *config.File) (*ini.Section, error) {
 	var candidates []*ini.Section
 	configuredHost, err := canonicalHost(cfg.Host)
 	if err != nil {
@@ -68,7 +69,7 @@ func resolveSection(cfg *config.Config, iniFile *ini.File) (*ini.Section, error)
 }
 
 func loadFromDatabricksCfg(cfg *config.Config) error {
-	iniFile, err := getDatabricksCfg()
+	iniFile, err := databrickscfg.Get()
 	if errors.Is(err, fs.ErrNotExist) {
 		// it's fine not to have ~/.databrickscfg
 		return nil

cmd/auth/login.go

@@ -61,7 +61,7 @@ func newLoginCommand(persistentAuth *auth.PersistentAuth) *cobra.Command {
 		}
 
 		// If the chosen profile has a hostname and the user hasn't specified a host, infer the host from the profile.
-		_, profiles, err := databrickscfg.LoadProfiles(databrickscfg.DefaultPath, func(p databrickscfg.Profile) bool {
+		_, profiles, err := databrickscfg.LoadProfiles(func(p databrickscfg.Profile) bool {
 			return p.Name == profileName
 		})
 		if err != nil {

cmd/auth/profiles.go

@@ -5,32 +5,16 @@ import (
 	"fmt"
 	"net/http"
 	"os"
-	"path/filepath"
-	"strings"
 	"sync"
 
 	"github.com/databricks/cli/libs/cmdio"
+	"github.com/databricks/cli/libs/databrickscfg"
 	"github.com/databricks/databricks-sdk-go"
 	"github.com/databricks/databricks-sdk-go/config"
 	"github.com/spf13/cobra"
 	"gopkg.in/ini.v1"
 )
 
-func getDatabricksCfg() (*ini.File, error) {
-	configFile := os.Getenv("DATABRICKS_CONFIG_FILE")
-	if configFile == "" {
-		configFile = "~/.databrickscfg"
-	}
-	if strings.HasPrefix(configFile, "~") {
-		homedir, err := os.UserHomeDir()
-		if err != nil {
-			return nil, fmt.Errorf("cannot find homedir: %w", err)
-		}
-		configFile = filepath.Join(homedir, configFile[1:])
-	}
-	return ini.Load(configFile)
-}
-
 type profileMetadata struct {
 	Name      string `json:"name"`
 	Host      string `json:"host,omitempty"`
@@ -111,10 +95,12 @@ func newProfilesCommand() *cobra.Command {
 
 	cmd.RunE = func(cmd *cobra.Command, args []string) error {
 		var profiles []*profileMetadata
-		iniFile, err := getDatabricksCfg()
+		iniFile, err := databrickscfg.Get()
 		if os.IsNotExist(err) {
 			// return empty list for non-configured machines
-			iniFile = ini.Empty()
+			iniFile = &config.File{
+				File: &ini.File{},
+			}
 		} else if err != nil {
 			return fmt.Errorf("cannot parse config file: %w", err)
 		}

cmd/root/auth.go

@@ -40,10 +40,7 @@ func MustAccountClient(cmd *cobra.Command, args []string) error {
 		// 1. only admins will have account configured
 		// 2. 99% of admins will have access to just one account
 		// hence, we don't need to create a special "DEFAULT_ACCOUNT" profile yet
-		_, profiles, err := databrickscfg.LoadProfiles(
-			databrickscfg.DefaultPath,
-			databrickscfg.MatchAccountProfiles,
-		)
+		_, profiles, err := databrickscfg.LoadProfiles(databrickscfg.MatchAccountProfiles)
 		if err != nil {
 			return err
 		}
@@ -124,8 +121,11 @@ func transformLoadError(path string, err error) error {
 }
 
 func askForWorkspaceProfile() (string, error) {
-	path := databrickscfg.DefaultPath
-	file, profiles, err := databrickscfg.LoadProfiles(path, databrickscfg.MatchWorkspaceProfiles)
+	path, err := databrickscfg.GetPath()
+	if err != nil {
+		return "", fmt.Errorf("cannot determine Databricks config file path: %w", err)
+	}
+	file, profiles, err := databrickscfg.LoadProfiles(databrickscfg.MatchWorkspaceProfiles)
 	if err != nil {
 		return "", transformLoadError(path, err)
 	}
@@ -156,8 +156,11 @@ func askForWorkspaceProfile() (string, error) {
 }
 
 func askForAccountProfile() (string, error) {
-	path := databrickscfg.DefaultPath
-	file, profiles, err := databrickscfg.LoadProfiles(path, databrickscfg.MatchAccountProfiles)
+	path, err := databrickscfg.GetPath()
+	if err != nil {
+		return "", fmt.Errorf("cannot determine Databricks config file path: %w", err)
+	}
+	file, profiles, err := databrickscfg.LoadProfiles(databrickscfg.MatchAccountProfiles)
 	if err != nil {
 		return "", transformLoadError(path, err)
 	}

libs/databrickscfg/profiles.go

@@ -1,7 +1,9 @@
 package databrickscfg
 
 import (
+	"fmt"
 	"os"
+	"path/filepath"
 	"strings"
 
 	"github.com/databricks/databricks-sdk-go/config"
@@ -64,12 +66,34 @@ func MatchAllProfiles(p Profile) bool {
 	return true
 }
 
-const DefaultPath = "~/.databrickscfg"
-
-func LoadProfiles(path string, fn ProfileMatchFunction) (file string, profiles Profiles, err error) {
-	f, err := config.LoadFile(path)
+// Get the path to the .databrickscfg file, falling back to the default in the current user's home directory.
+func GetPath() (string, error) {
+	configFile := os.Getenv("DATABRICKS_CONFIG_FILE")
+	if configFile == "" {
+		configFile = "~/.databrickscfg"
+	}
+	if strings.HasPrefix(configFile, "~") {
+		homedir, err := os.UserHomeDir()
 		if err != nil {
-		return
+			return "", fmt.Errorf("cannot find homedir: %w", err)
+		}
+		configFile = filepath.Join(homedir, configFile[1:])
+	}
+	return configFile, nil
+}
+
+func Get() (*config.File, error) {
+	configFile, err := GetPath()
+	if err != nil {
+		return nil, fmt.Errorf("cannot determine Databricks config file path: %w", err)
+	}
+	return config.LoadFile(configFile)
+}
+
+func LoadProfiles(fn ProfileMatchFunction) (file string, profiles Profiles, err error) {
+	f, err := Get()
+	if err != nil {
+		return "", nil, fmt.Errorf("cannot load Databricks config file: %w", err)
 	}
 
 	homedir, err := os.UserHomeDir()
@@ -106,7 +130,7 @@ func LoadProfiles(path string, fn ProfileMatchFunction) (file string, profiles P
 }
 
 func ProfileCompletion(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
-	_, profiles, err := LoadProfiles(DefaultPath, MatchAllProfiles)
+	_, profiles, err := LoadProfiles(MatchAllProfiles)
 	if err != nil {
 		return nil, cobra.ShellCompDirectiveError
 	}

libs/databrickscfg/profiles_test.go

@@ -32,19 +32,22 @@ func TestLoadProfilesReturnsHomedirAsTilde(t *testing.T) {
 	} else {
 		t.Setenv("HOME", "./testdata")
 	}
-	file, _, err := LoadProfiles("./testdata/databrickscfg", func(p Profile) bool { return true })
+	t.Setenv("DATABRICKS_CONFIG_FILE", "./testdata/databrickscfg")
+	file, _, err := LoadProfiles(func(p Profile) bool { return true })
 	require.NoError(t, err)
 	assert.Equal(t, "~/databrickscfg", file)
 }
 
 func TestLoadProfilesMatchWorkspace(t *testing.T) {
-	_, profiles, err := LoadProfiles("./testdata/databrickscfg", MatchWorkspaceProfiles)
+	t.Setenv("DATABRICKS_CONFIG_FILE", "./testdata/databrickscfg")
+	_, profiles, err := LoadProfiles(MatchWorkspaceProfiles)
 	require.NoError(t, err)
 	assert.Equal(t, []string{"DEFAULT", "query", "foo1", "foo2"}, profiles.Names())
 }
 
 func TestLoadProfilesMatchAccount(t *testing.T) {
-	_, profiles, err := LoadProfiles("./testdata/databrickscfg", MatchAccountProfiles)
+	t.Setenv("DATABRICKS_CONFIG_FILE", "./testdata/databrickscfg")
+	_, profiles, err := LoadProfiles(MatchAccountProfiles)
 	require.NoError(t, err)
 	assert.Equal(t, []string{"acc"}, profiles.Names())
 }