fix: use Repo.transaction instead of non-existent Repo.transact

patterns/multi.md

@@ -17,18 +17,18 @@ def reset(account, params) do
 end
 
 # Execute:
-case Repo.transact(PasswordManager.reset(account, params)) do
+case Repo.transaction(PasswordManager.reset(account, params)) do
   {:ok, %{account: account, log: log}} -> # success
   {:error, :account, changeset, _} -> # account step failed
 end
 ```
 
-**Why:** Each operation is named. On success, `Repo.transact` returns `{:ok, results_map}` where each key is the name given to that operation. On failure, it returns `{:error, failed_name, failed_value, changes_so_far}`, making it immediately clear which step aborted the transaction and why. This is more precise than a bare transaction function where you'd have to inspect the return value to guess which step failed.
+**Why:** Each operation is named. On success, `Repo.transaction` returns `{:ok, results_map}` where each key is the name given to that operation. On failure, it returns `{:error, failed_name, failed_value, changes_so_far}`, making it immediately clear which step aborted the transaction and why. This is more precise than a bare transaction function where you'd have to inspect the return value to guess which step failed.
 
 **Anti-pattern:** Using an anonymous function with bare `case` statements inside a transaction, where failure attribution is implicit:
 ```elixir
 # BAD — no way to know which operation failed from the return value alone
-Repo.transact(fn ->
+Repo.transaction(fn ->
   case Repo.update(Account.password_reset_changeset(account, params)) do
     {:ok, account} ->
       case Repo.insert(Log.password_reset_changeset(account, params)) do
@@ -50,7 +50,7 @@ end)
 **Example — before:**
 ```elixir
 def create_user_with_profile(params) do
-  Repo.transact(fn ->
+  Repo.transaction(fn ->
     case Repo.insert(User.changeset(params)) do
       {:ok, user} ->
         case Repo.insert(Profile.changeset(user, params)) do
@@ -71,7 +71,7 @@ def create_user_with_profile(params) do
   |> Multi.insert(:profile, fn %{user: user} ->
     Profile.changeset(user, params)
   end)
-  |> Repo.transact()
+  |> Repo.transaction()
 end
 
 # Caller:
@@ -86,7 +86,7 @@ end
 
 **Don't use this when:**
 - You have a single database operation (just call `Repo.insert/update/delete` directly)
-- Operations are simple and sequential with no branching (a plain `Repo.transact(fn -> ... end)` is more readable)
+- Operations are simple and sequential with no branching (a plain `Repo.transaction(fn -> ... end)` is more readable)
 - The overhead of building a Multi struct is not justified by the number of operations
 
 **Over-application example:**
@@ -94,7 +94,7 @@ end
 # Overkill for a single operation
 Multi.new()
 |> Multi.insert(:user, User.changeset(params))
-|> Repo.transact()
+|> Repo.transaction()
 ```
 
 **Better alternative:**
@@ -102,7 +102,7 @@ Multi.new()
 Repo.insert(User.changeset(params))
 ```
 
-**Why:** `Ecto.Multi` introduces indirection. For simple cases, calling Repo functions directly or using `Repo.transact(fn -> ... end)` is clearer. The named-pipeline form pays off when 3+ operations are involved and failure attribution matters.
+**Why:** `Ecto.Multi` introduces indirection. For simple cases, calling Repo functions directly or using `Repo.transaction(fn -> ... end)` is clearer. The named-pipeline form pays off when 3+ operations are involved and failure attribution matters.
 
 ---
 
@@ -144,7 +144,7 @@ end)
 **Example — before:**
 ```elixir
 def register_user(params) do
-  Repo.transact(fn ->
+  Repo.transaction(fn ->
     {:ok, user} = Repo.insert(User.changeset(params))
     # This runs outside Multi — if it fails, user was already inserted
     case ExternalService.provision(user.id) do
@@ -163,7 +163,7 @@ def register_user(params) do
   |> Multi.run(:provision, fn _repo, %{user: user} ->
     ExternalService.provision(user.id)
   end)
-  |> Repo.transact()
+  |> Repo.transaction()
 end
 ```
 
@@ -496,7 +496,7 @@ Enum.reduce(accounts, Multi.new(), fn account, multi ->
 end)
 
 # Error pattern-matching:
-case Repo.transact(multi) do
+case Repo.transaction(multi) do
   {:ok, results} -> Map.keys(results)  # [{:account, 1}, {:account, 2}, ...]
   {:error, {:account, id}, changeset, _} -> "account #{id} failed"
 end
@@ -547,7 +547,7 @@ def reset_passwords(accounts, params) do
 end
 
 # Caller knows exactly which account failed:
-case Repo.transact(reset_passwords(accounts, params)) do
+case Repo.transaction(reset_passwords(accounts, params)) do
   {:ok, _} -> :ok
   {:error, {:account, id}, changeset, _} ->
     Logger.error("Failed to reset account #{id}: #{inspect(changeset.errors)}")
@@ -609,7 +609,7 @@ test "password reset changeset is valid" do
   account = %Account{password: "letmein"}
   {:ok, %{account: updated}} =
     PasswordManager.reset(account, valid_params)
-    |> Repo.transact()
+    |> Repo.transaction()
 
   # The changeset validity was the whole point, not the DB state
   assert updated.password != account.password
@@ -630,7 +630,7 @@ end
 test "creates user with profile" do
   {:ok, %{user: user, profile: profile}} =
     UserRegistration.multi(valid_params())
-    |> Repo.transact()
+    |> Repo.transaction()
 
   assert user.email == "test@example.com"
   assert profile.user_id == user.id
@@ -685,7 +685,7 @@ test "comment changeset is valid given a post" do
 end
 ```
 
-**Why:** `Multi.to_list/1` reflects the state of the pipeline at build time. Deferred values (function variants, `Multi.run` callbacks, `Multi.merge` functions) are not evaluated until `Repo.transact` runs them. Test those deferred pieces independently rather than trying to inspect them through `to_list`.
+**Why:** `Multi.to_list/1` reflects the state of the pipeline at build time. Deferred values (function variants, `Multi.run` callbacks, `Multi.merge` functions) are not evaluated until `Repo.transaction` runs them. Test those deferred pieces independently rather than trying to inspect them through `to_list`.
 
 ---
 
@@ -697,6 +697,6 @@ end
 - If you have reusable Multi fragments to combine → `Multi.append/2` or `Multi.prepend/2`
 - If you're updating a dynamic collection → tuple keys `{:operation, id}`
 - If you want to validate changesets without hitting the DB → `Multi.to_list/1` in tests
-- If operations are simple and static (no dynamic branching) → consider `Repo.transact(fn -> ... end)` instead
+- If operations are simple and static (no dynamic branching) → consider `Repo.transaction(fn -> ... end)` instead
 
 <!-- PATTERN_COMPLETE -->