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Extend DAML Script migration guide (#7448)

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* Extend DAML Script migration guide

This PR extends the DAML Script migration guide with a few things that
have been added recently or popped up during the migration of various
refapps.

fixes #7403

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* Apply suggestions from code review

Co-authored-by: Martin Huschenbett <martin.huschenbett@posteo.me>

* Rename daml on sql to daml for postgresql

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* Update docs/source/daml-script/index.rst

Co-authored-by: Martin Huschenbett <martin.huschenbett@posteo.me>

Co-authored-by: Martin Huschenbett <martin.huschenbett@posteo.me>
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Moritz Kiefer 2020-09-21 15:23:56 +02:00 committed by GitHub
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@ -235,15 +235,44 @@ translated to DAML script but there are a few things to keep in mind:
#. Instead of specifying a ``scenario`` field in your ``daml.yaml``,
you need to specify an ``init-script`` field. The initialization
script is specified via ``Module:identifier`` for both fields.
#. DAML script only supports the commands available on the ledger API
so you cannot call functions like ``fetch`` directly. This is
intentional. Your initialization scripts should not be able to
create transactions that a ledger client would not be able to
create. If you want to call methods not exposed via the Ledger API,
you can create a new template with a single choice
and call that via ``createAndExercise``.
#. You need to replace calls to ``getParty x`` by
``allocatePartyWithHint x (PartyIdHint x)``.
#. In DAML script, ``submit`` and ``submitMustFail`` are limited to
the functionality provided by the ledger API: A list of independent
commands consisting of ``createCmd``, ``exerciseCmd``,
``createAndExerciseCmd`` and ``exerciseByKeyCmd``. There are two
issues you might run into when migrating an existing scenario:
#. Your commands depend on each other, e.g., you use the result of
a ``create`` within a following command in the same
``submit``. In this case, you have two options: If it is not
important that they are part of a single transaction, split
them into multiple calls to ``submit``. If you do need them to
be within the same transaction, you can move the logic to a
choice and call that using ``createAndExerciseCmd``.
#. You use something that is not part of the 4 ledger API command
types, e.g., ``fetch``. For ``fetch`` and ``fetchByKey``, you
can instead use ``queryContractId`` and ``queryContractKey``
with the caveat that they do not run within the same
transaction. Other types of ``Update`` statements can be moved
to a choice that you call via ``createAndExerciseCmd``.
#. Instead of Scenario’s ``getParty``, DAML Script provides you with
``allocateParty`` and ``allocatePartyWithHint``. There are a few
important differences:
#. Allocating a party always gives you back a new party (or
fails). If you have multiple calls to ``getParty`` with the same
string and expect to get back the same party, you should instead
allocate the party once at the beginning and pass it along to
the rest of the code.
#. If you want to allocate a party with a specific party id, you
can use ``allocatePartyWithHint x (PartyIdHint x)`` as a replacement for `getParty x`. Note that
while this is supported in DAML Studio and DAML for PostgreSQL, other
ledgers can behave differently and ignore the party id hint or
interpret it another way. Try to not rely on any specific
party id.
#. Instead of ``pass`` and ``passToDate``, DAML Script provides
``passTime`` and ``setTime``.
.. _daml-script-distributed: