View source for LDT/User Area/Tutorial/Create a simple Execution Environment

In this tutorial, I will show how to create a simple EE. See also [[LDT/User_Area/Execution_Environment_file_format|EE detailed documentation]].

== What is an EE ? ==

<blockquote>An Execution Environment, is a file containing information about the environment where a Lua application is supposed to be run. An environment is a set of libraries and global variables available to the application out of the box, as in ''Lua 5.1'' or ''MOAI SDK''. Only one Execution Environment is expected per project.
The idea is to provide a file which describe elements of an environment. Provided information allows LDT to offer better code completion, code navigation and documentation layout.</blockquote>
Extract from [[LDT/User_Area/User_Guides/User_Guide_1.2#Execution_Environment| User Guide]].

== Why this tutorial ? ==
Suppose that you have made a custom interpreter based on Lua 5.1 interpreter and you added the [http://keplerproject.github.io/luafilesystem/index.html LuaFileSystem] library in it. That means while using the interpreter there is no needs to install LFS using LuaRocks or require it as the module is preloaded in the global variable '''lfs'''. Then while codding on LDT, you don't have any user-assistance on the LFS library, this is because your EE doesn't contain a description of the LFS library. In the following steps you can learn how to create a simple EE to enable user assistance on the LFS library.

If you have just put a library like LFS in the path, with LuaRocks for exemple, you just need to put a '''.doclua''' file representing the LFS library in your project buildpath. See the third step to see how to write the '''.luadoc''' file.

== Step1: Get the source ==
#Get the Lua-5.1 standard EE sources. Actually, there is no easy way to get it, but here two methods:
#*Clone the [https://git.eclipse.org/c/ldt/org.eclipse.ldt.git/ git repository] and copy the folder ''org.eclipse.ldt/plugins/org.eclipse.ldt.support.lua51/src-ee/lua-5.1''
#*Find the local path by expending a Lua51 Execution Environment in a LDT project and copy the folder '''lua-5.1''':
<center>[[File:EEPath.jpg]]</center>
#Rename the folder '''lua-5.1''' into '''lualfs'''
#Extract the '''lualfs/api.zip''' archive into an '''lualfs/api''' folder.

== Step2: Rockspec file ==
Edit '''name''' and '''description''' as follow.
<source lang="lua">
package = "lfslua"
version = "5.1"
grammar = "lua-5.1"
flags = { ee = true }
description = {
  summary = "Lua 5.1 with LFS Execution Environment",
  detailed = [[Lua 5.1 with LFS Execution Environment Support]],
  licence = "EPL-MIT",
  homepage= "http://eclipse.org/ldt"
}
api = {
  file = "api.zip"
}
documentation = {
  dir="docs"
}
</source>

You can find more about the rockspec file, in the [[LDT/User_Area/Execution_Environment_file_format|related documentation]].

== Step 3: Write your module doclua ==
Create a new '''doclua''' file in the api folder. You can edit it in the '''LDT''' to have syntax coloring and code completion.

<pre>
Declare the module
--- @module lfs
</pre>

Let's comment a function. Here the explanation for '''mkdir''', but it's the same for each functions.

Here the definition of mkdir function from the LFS manual:
<blockquote>
lfs.mkdir (dirname)<br>
:Creates a new directory. The argument is the name of the new directory.
:Returns true if the operation was successful; in case of error, it returns nil plus an error string.
</blockquote>

Translate it in [[LDT/User_Area/Documentation_Language|Documentation Language]].
Put the description first:
<pre>
--- Creates a new directory.
</pre>

Set the function name
<pre>
-- @function [parent=#lfs]mkdir
</pre>

Declare the parameter:
<pre>
-- @param #string dirname name of the new directory
</pre>

Declare returns
<pre>
-- @return true If the operation was successful
-- @return nil, #string In case of error
</pre>

Add following statement at the end of the file (Due to an LDT limitation, files have to contain valid Lua statement to be taken in account)
<pre>
return nil.
</pre>

== Step 4: Declare global variable ==
If your interpreter preload some module in some '''global variable''', you should declare them in the global.doclua file as follow:
<pre>
---
-- This library provides generic functions for file manipulation.
-- This is a global variable which hold the preloaded @{lfs} module.
-- @field[parent = #global] lfs#lfs lfs preloaded module
</pre>

*The ''parent = #global'' indicate that we are declaring a global var.
*The ''lfs#lfs'' is a external reference to the ''lfs'' module.

== Step 5: Zip and test ==
# Zip the lualfs/api folder into lualfs/api.zip.
# Zip the lualfs folder.
# Import the archive as a new EE.
# Create a new project with this new EE.
# Test the auto-completion after ''lfs.''

== Going further ==

=== Step 6: Advanced users: Use Lua documentor to generate the documentation. ===
To be written

=== Step 7:  Add a default project template in your EE. ===
To be written

== Questions ==
If you have some questions or commentaries, please respond this topic on the [https://www.eclipse.org/forums/index.php/m/1697588/#msg_1697588 forum].