test(config): clarify provider transaction publication results

Describe whole-document repair publication accurately and document committed results on lock release errors. Strengthen publication-failure coverage with an existing provider row, zero result, unchanged config, and restored credential assertions. Removing the zero-result guard fails the targeted regression.

Amp-Thread-ID: https://ampcode.com/threads/T-01a0e862-4304-73bb-9aee-5e56cb537f3a
Co-authored-by: Pierre Bruno <pierrebruno@hotmail.ch>

Author: ampagent

internal/config/provider_commit.go

@@ -48,8 +48,9 @@ var acquireProviderWriteLock = lockProviderWrite
 // config stays invalid because the row cannot be removed. Operations that ADD
 // or publish state pass false, so a new profile or credential is never written
 // into a config whose persisted names are already ambiguous. When it is true
-// the publish also goes through writeProviderNameRepair, which rewrites only
-// the fields this operation changed instead of restating the whole file.
+// the publish goes through writeProviderNameRepair, which re-encodes the whole
+// config but permits remaining invalid names only when the operation strictly
+// reduces existing name problems without introducing or worsening another.
 func runProviderProfileOperation(path string, allowMissing bool, allowInvalidInput bool, mutate func(*providerProfileOperation) error) (result FileConfig, err error) {
 	path = strings.TrimSpace(path)
 	if path == "" {
@@ -229,6 +230,8 @@ type ProviderCommit struct {
 // ProviderCommitResult reports the config as written and the profile exactly as
 // it was persisted: the adopted name, and the key moved into the credential
 // store (APIKey cleared, APIKeyStored set) unless KeepStoredKey was requested.
+// A nonzero result alongside an error means publication succeeded but lock
+// release failed; a rejected mutation or publication returns the zero result.
 type ProviderCommitResult struct {
 	Config    FileConfig
 	Persisted ProviderProfile

internal/config/provider_commit_test.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"reflect"
 	"runtime"
 	"strings"
 	"sync"
@@ -458,6 +459,8 @@ func TestCommitProviderProfileRollsBackKeyWhenPublicationFails(t *testing.T) {
 	dir := t.TempDir()
 	t.Setenv("ZERO_CRED_STORAGE", "encrypted-file")
 	path := filepath.Join(dir, "config.json")
+	before := FileConfig{Providers: []ProviderProfile{{Name: "work", APIKeyStored: true}}}
+	writeConfigFixture(t, path, before, 0o600)
 	store, err := ProviderKeyStoreAt(dir)
 	if err != nil {
 		t.Fatal(err)
@@ -469,9 +472,16 @@ func TestCommitProviderProfileRollsBackKeyWhenPublicationFails(t *testing.T) {
 	publishProviderConfig = func(string, FileConfig) error { return errors.New("disk full") }
 	t.Cleanup(func() { publishProviderConfig = oldPublish })
 
-	if _, err := CommitProviderProfile(path, ProviderCommit{Profile: ProviderProfile{Name: "work", APIKey: "sk-new"}}); err == nil {
+	result, err := CommitProviderProfile(path, ProviderCommit{Profile: ProviderProfile{Name: "work", APIKey: "sk-new"}})
+	if err == nil {
 		t.Fatal("CommitProviderProfile error = nil, want publication failure")
 	}
+	if !reflect.DeepEqual(result, ProviderCommitResult{}) {
+		t.Fatalf("rejected publication returned a committed result: %+v", result)
+	}
+	if got := readConfigFixture(t, path); !reflect.DeepEqual(got, before) {
+		t.Fatalf("rejected publication changed config: %+v", got)
+	}
 	if key, ok, err := store.Get("work"); err != nil || !ok || key != "sk-original" {
 		t.Fatalf("rollback key = %q ok=%v err=%v, want original", key, ok, err)
 	}