Fix MSAL caching (#2300)

This change updates our MSAL cache adapter to no longer use the hinted partition key as a cache key. Instead, the current user has a fixed cache key equal to the empty string `""`. This creates the behavior of `~/.azd/auth/msal/cache.[bin|json]` being the single file that contains MSAL multi-account data, as defined by this [contract](https://github.com/AzureAD/microsoft-authentication-library-for-go/blob/27c98c8f9db6bc564c5be43677f3e6276b7c4fef/apps/internal/base/internal/storage/items.go#L18).

Also, fix logout not resetting `cache.json` due to using `config.json` (userConfigManger.Load) and not `auth.json` (readAuthConfig).

Fixes #2299

cli/azd/pkg/auth/cache.go

@@ -10,13 +10,26 @@ import (
 	"github.com/AzureAD/microsoft-authentication-library-for-go/apps/cache"
 )
 
+// The MSAL cache key for the current user. The stored MSAL cached data contains
+// all accounts with stored credentials, across all tenants.
+// Currently, the underlying MSAL cache data is represented as [Contract] inside the library.
+//
+// For simplicity in naming the final cached file, which has a unique directory (see [fileCache]),
+// and for historical purposes, we use empty string as the key.
+//
+// It may be tempting to instead use the partition key provided by [cache.ReplaceHints],
+// but note that the key is a partitioning key and not a unique user key.
+// Also, given that the data contains auth data for all users, we only need a single key
+// to store all cached auth information.
+const cCurrentUserCacheKey = ""
+
 // msalCacheAdapter adapts our interface to the one expected by cache.ExportReplace.
 type msalCacheAdapter struct {
 	cache Cache
 }
 
-func (a *msalCacheAdapter) Replace(ctx context.Context, cache cache.Unmarshaler, cacheHints cache.ReplaceHints) error {
-	val, err := a.cache.Read(cacheHints.PartitionKey)
+func (a *msalCacheAdapter) Replace(ctx context.Context, cache cache.Unmarshaler, _ cache.ReplaceHints) error {
+	val, err := a.cache.Read(cCurrentUserCacheKey)
 	if errors.Is(err, errCacheKeyNotFound) {
 		return nil
 	} else if err != nil {
@@ -30,13 +43,13 @@ func (a *msalCacheAdapter) Replace(ctx context.Context, cache cache.Unmarshaler,
 	return nil
 }
 
-func (a *msalCacheAdapter) Export(ctx context.Context, cache cache.Marshaler, cacheHints cache.ExportHints) error {
+func (a *msalCacheAdapter) Export(ctx context.Context, cache cache.Marshaler, _ cache.ExportHints) error {
 	val, err := cache.Marshal()
 	if err != nil {
 		return err
 	}
 
-	return a.cache.Set(cacheHints.PartitionKey, val)
+	return a.cache.Set(cCurrentUserCacheKey, val)
 }
 
 type Cache interface {

cli/azd/pkg/auth/cache_test.go

@@ -5,66 +5,69 @@ package auth
 
 import (
 	"context"
+	"math/rand"
 	"testing"
 
 	"github.com/AzureAD/microsoft-authentication-library-for-go/apps/cache"
 	"github.com/stretchr/testify/require"
 )
 
+var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
+
+func randSeq(n int, rng rand.Rand) string {
+	b := make([]rune, n)
+	for i := range b {
+		b[i] = letters[rng.Intn(len(letters))]
+	}
+	return string(b)
+}
+
 func TestCache(t *testing.T) {
 	root := t.TempDir()
 	ctx := context.Background()
 	c := newCache(root)
+	// weak rng is fine for testing
+	//nolint:gosec
+	rng := rand.New(rand.NewSource(0))
 
-	d1 := fixedMarshaller{
-		val: []byte("some data"),
+	key := func() string {
+		return randSeq(10, *rng)
 	}
 
-	d2 := fixedMarshaller{
-		val: []byte("some different data"),
+	data := fixedMarshaller{
+		val: []byte("some data"),
 	}
 
 	// write some data.
-	err := c.Export(ctx, &d1, cache.ExportHints{PartitionKey: "d1"})
+	err := c.Export(ctx, &data, cache.ExportHints{PartitionKey: key()})
 	require.NoError(t, err)
-	err = c.Export(ctx, &d2, cache.ExportHints{PartitionKey: "d2"})
-	require.NoError(t, err)
-
-	var r1 fixedMarshaller
-	var r2 fixedMarshaller
 
 	// read back that data we wrote.
-	err = c.Replace(ctx, &r1, cache.ReplaceHints{PartitionKey: "d1"})
+	var reader fixedMarshaller
+	err = c.Replace(ctx, &reader, cache.ReplaceHints{PartitionKey: key()})
 	require.NoError(t, err)
-	err = c.Replace(ctx, &r2, cache.ReplaceHints{PartitionKey: "d2"})
-	require.NoError(t, err)
-
-	require.NotNil(t, r1.val)
-	require.NotNil(t, r2.val)
-	require.Equal(t, d1.val, r1.val)
-	require.Equal(t, d2.val, r2.val)
+	require.NotNil(t, reader.val)
+	require.Equal(t, data.val, reader.val)
 
 	// the data should be shared across instances.
 	c = newCache(root)
-
-	err = c.Replace(ctx, &r1, cache.ReplaceHints{PartitionKey: "d1"})
-	require.NoError(t, err)
-	err = c.Replace(ctx, &r2, cache.ReplaceHints{PartitionKey: "d2"})
+	reader = fixedMarshaller{}
+	err = c.Replace(ctx, &reader, cache.ReplaceHints{PartitionKey: key()})
 	require.NoError(t, err)
+	require.Equal(t, data.val, reader.val)
 
-	require.NotNil(t, r1.val)
-	require.NotNil(t, r2.val)
-	require.Equal(t, d1.val, r1.val)
-	require.Equal(t, d2.val, r2.val)
-
-	// read some non-existing data
-	nonExist := fixedMarshaller{
-		val: []byte("some data"),
+	// update existing data
+	otherData := fixedMarshaller{
+		val: []byte("other data"),
 	}
-	err = c.Replace(ctx, &nonExist, cache.ReplaceHints{PartitionKey: "nonExist"})
+	err = c.Export(ctx, &otherData, cache.ExportHints{PartitionKey: key()})
+	require.NoError(t, err)
+
+	// read back data
+	err = c.Replace(ctx, &reader, cache.ReplaceHints{PartitionKey: key()})
 	require.NoError(t, err)
-	// data should not be overwritten when key is not found.
-	require.Equal(t, []byte("some data"), nonExist.val)
+	require.NotNil(t, reader.val)
+	require.Equal(t, otherData.val, reader.val)
 }
 
 func TestCredentialCache(t *testing.T) {

cli/azd/pkg/auth/manager.go

@@ -585,7 +585,7 @@ func (m *Manager) saveLoginForServicePrincipal(tenantId, clientId string, secret
 // getSignedInAccount fetches the public.Account for the signed in user, or nil if one does not exist
 // (e.g when logged in with a service principal).
 func (m *Manager) getSignedInAccount(ctx context.Context) (*public.Account, error) {
-	cfg, err := m.userConfigManager.Load()
+	cfg, err := m.readAuthConfig()
 	if err != nil {
 		return nil, fmt.Errorf("fetching current user: %w", err)
 	}