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nickchapman-da d81caa9568
rework daml_compile bazel rule (#5070) 
Avoiding `damlc compile/package` commands (which we would like to deprecate), and replace with plain `damlc build` together with a post dar->dalf extraction step in the couple of places where we actually want the .dalf for testing.

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2020-03-18 23:06:55 +00:00
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src forbid non-generic comparison in 1.dev (#5020) 2020-03-16 17:25:43 +00:00
archive.bzl update copyright notices to 2020 (#3939) 2020-01-02 21:21:13 +01:00
BUILD.bazel rework daml_compile bazel rule (#5070) 2020-03-18 23:06:55 +00:00
README.md daml-lf proto: archive proto for daml-lf 1.6 (#3142) 2019-10-15 18:35:20 +00:00

README.md

DAML-LF archive

This component contains the .proto definitions specifying the format in which DAML-LF packages are stored -- the DAML-LF archive. All the proto definitions are kept in the directory src/protorotobuf/com/digitalasset/daml_lf_dev/

The entry point definition is Archive in src/protorotobuf/com/digitalasset/daml_lf_dev/daml_lf.proto. Archive contains some metadata about the actual archive (currently the hashing function and the hash), and then a binary blob containing the archive. The binary blob must be an ArchivePayload -- we keep it in binary form to facilitate hashing, signing, etc. The encoding and decoding of the payload is handled by Haskell and Java libraries in daml-core-package, so that consumers and producers do not really need to worry about it.

ArchivePayload is a sum type containing the various DAML-LF versions supported by the DAML-LF archive. Currently we have two major versions:

Snapshot versions

The component contains also an arbitrary number of snapshots of the protobuf definitions as they were as the time a particular version of DAML-LF was frozen. Those snapshots are kept in the directories src/protorotobuf/com/digitalasset/daml_lf_x_y/, where x.y is a already frozen DAML-LF version. A snapshot for version x.y can be used to read any DAML-LF version from 1.0 to x.y without suffering breaking changes (at the generated code level) often introduced in the current version.

Building

It produces several libraries containing code to encode / decode such definition, a Haskell one, and several Java ones:

$ bazel build //daml-lf/archive:daml_lf_archive_haskell_proto
$ bazel build //daml-lf/archive:daml_lf_dev_archive_java_proto
$ bazel build //daml-lf/archive:daml_lf_1_6_archive_java_proto

Editing the .proto definitions

When editing the proto definitions, you must make sure to not change them in a backwards-incompatible way. To make sure this doesn't happen:

  • DO NOT delete message fields;
  • DO NOT change the number of a message field or an enum value;
  • DO NOT change the type of a message field;

Note that "fields" include oneof fields. Also note that the "don't delete fields" rule is there not because they introduce a backwards incompatible change, but rather because after a field has been deleted another commiter might redefine it with a different type without realizing.

What is OK is renaming message fields while keeping the number and semantics unchanged. For example, if you have

message Foo {
  bytes blah = 1;
}

it's OK to change it to

message Foo {
  // this field is deprecated -- use baz instead!
  bytes blah_deprecated = 1;
  string baz = 2;
}

Conversion from the .proto to AST

The .proto definitions contain the serialized format for DAML-LF packages, however the code to convert from the .proto definitions to the actual AST lives elsewhere.