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Imports And Exports

An Aqua source file has a header and a body. The body contains function definitions, services, types, constants. The header manages what is imported from other files and what is exported.

Aqua source file header​

When header is omitted, .aqua file exports and declares everything it contains. With aqua header you can control what gets exported from the aqua file.

aqua
-- `aqua` expression may be only on the very first line of the file
aqua AquaFile declares *
aqua
-- `aqua` expression may be only on the very first line of the file
aqua AquaFile declares *

Aqua.File may contain dots.

AquaFile can be used as the aqua's name when this file is used. In this case, only what is enumerated in declares section will be available. declares * allows you to declare everything in the file as the module interface.

aqua
aqua AquaFile declares CONST_NAME, ServiceName, MyType, fn
const CONST_NAME = "something"
service ServiceName:
  do_something()
  
data MyType:
  result: i32  
function fn() -> string:
  <- CONST_NAME
aqua
aqua AquaFile declares CONST_NAME, ServiceName, MyType, fn
const CONST_NAME = "something"
service ServiceName:
  do_something()
  
data MyType:
  result: i32  
function fn() -> string:
  <- CONST_NAME

Import Expression​

The main way to import a file is via import expression:

aqua
import "@fluencelabs/aqua-lib/builtin.aqua"
func foo():
  Op.noop()
aqua
import "@fluencelabs/aqua-lib/builtin.aqua"
func foo():
  Op.noop()

Aqua compiler takes a source directory and a list of import directories (usually with node_modules as a default). You can use relative paths to .aqua files, relatively to the current file's path, and to import folders.

info

.aqua extension in import and use expressions can be omitted. So, import "builtin.aqua" does exactly the same as import "builtin".

Everything defined in the file is imported into the current namespace.

You can cherry-pick and rename imports using import ... from expression:

aqua
import Op as Noop from "@fluencelabs/aqua-lib/builtin"
func foo():
  Noop.noop()
aqua
import Op as Noop from "@fluencelabs/aqua-lib/builtin"
func foo():
  Noop.noop()

Use Expression​

The use expression makes it possible to import a file into a named scope.

aqua
use Op from "@fluencelabs/aqua-lib/builtin" as BuiltIn
func foo():
  BuiltIn.Op.noop()
aqua
use Op from "@fluencelabs/aqua-lib/builtin" as BuiltIn
func foo():
  BuiltIn.Op.noop()

If the imported file has a aqua header, from and as sections of use may be omitted.

aqua
use "@fluencelabs/aqua-lib/builtin.aqua"
-- Assume that builtin.aqua's header is `aqua BuiltIn declares *`
func foo():
  BuiltIn.Op.noop()
aqua
use "@fluencelabs/aqua-lib/builtin.aqua"
-- Assume that builtin.aqua's header is `aqua BuiltIn declares *`
func foo():
  BuiltIn.Op.noop()

Export​

While it's useful to split the code into several functions into different files, it's not always a good idea to compile everything into the host language.

Another problem is libraries distribution. If a developer wants to deliver an .aqua library, he or she often needs to provide it in compiled form as well.

export lets a developer decide what exactly is going to be exported, including imported functions.

aqua
import bar from "lib"
-- Exported functions and services will be compiled for the host language
-- You can use several `export` expressions
export foo as my_foo
export bar, MySrv
service MySrv:
  call_something()
func foo() -> bool:
  <- true  
aqua
import bar from "lib"
-- Exported functions and services will be compiled for the host language
-- You can use several `export` expressions
export foo as my_foo
export bar, MySrv
service MySrv:
  call_something()
func foo() -> bool:
  <- true