Rell 0.10.0 release notes.txt

RELEASE NOTES 0.10.0 (2019-11-04)


Upgrade instructions: http://rell.chromia.com/en/0.10.0/languageguide/migration-0.10.html


1. Language: Module system

Docs: http://rell.chromia.com/en/0.10.0/languageguide/modules.html

The new module system replaces the "include" directive as a way to combine multiple .rell files into an application.

Highlights:

- A Rell application is a set of modules
- A module can be either a single .rell file or a directory with multiple .rell files
- Modules can import each other
- Rell files within a directory-module see each other's definitions and are imported as a single module


2. Language: Entities and structs

Classes renamed to entities and records renamed to structs:

entity user {
    name;
    company;
}

struct module_args {
    chain_name: text;
}

Existing code with classes and records will not compile.

To help fixing the code, there is a tool migrate-v0.10.sh. The tool replaces class/record by entity/struct, as well
as replaces most of deprecated library functions. The tool can be found in the postchain-node directory of
a Rell distribution.


3. Language: @mount annotation

Docs: http://rell.chromia.com/en/0.10.0/languageguide/general.html#mount-names

Mount names are defined for entities, objects, operations and queries:

- for entities and objects, that's the name of an SQL table where the data is stored
- for operations and queries, that's a name used to invoke an operation or a query from the outside

By default, a mount name of a definition is defined by its fully-qualified name (namespace path + definition name).

The new @mount annotation is used to specify an arbitrary mount name for a definition:

@mount('foo.bar.user') entity user {}


4. Language: Annotations syntax

Following the example of the @mount annotation, the old log annotation is now written the same way:

@log entity user {}

instead of

entity user (log) {}

(the old syntax is still allowed, but deprecated)


5. Language: Anonymous namespace

An anonymous (without a name) namespace allows to apply an annotation to a set of definitions:

@mount('foo'bar')
namespace {
    entity user {}
    entity company {}
}


6. Language: Name inference from qualified type name

Rell always allowed to not specify a type or a name if they are the same:

entity balance { account; asset; }

is equivalent to

entity balance { account: account; asset: asset; }

However, sometimes a type is defined in a namespace or in another module, so the code becomes:

entity balance { foo.account; bar.asset; }

Now such notation is also supported, and the code is equivalent to

entity balance { account: foo.account; asset: bar.asset; }

Works also for variables, parameters and nullable types:

operation o(foo.user?) {} // same as "user: foo.user?"


7. Language: Tuple fields access by index

Now following code will work:

val t = (123, 'Hello');
print(t[0]);
print(t[1]);


8. Compiler: Not stopping on first compilation error

Now Rell compiler (and Eclipse IDE) can report multiple semantic compilation errors per .rell file.


9. Library: Function byte_array.sha256()

A new member function sha256() for the byte_array type has been added.

Code examples:

'foo'.to_bytes().sha256() => byte_array[2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae]
'bar'.to_bytes().sha256() => byte_array[fcde2b2edba56bf408601fb721fe9b5c338d10ee429ea04fae5511b68fbf8fb9]


10. Library: Retirement of deprecated functions

Previously deprecated functions and types now are completely deprecated and cannot be used.

Existing code can be (partially) fixed with the migrate-v0.10.sh tool.