How to Enable Semantic Code Completion¶

Semantic code completion is now part of Spoofax 3.

Enabling Semantic Code Completion¶

To enable support for semantic code completion in your language:

Add the following to your language's spoofaxc.cfg file:
```
tego-runtime {}
code-completion {}
```

Declare the following strategies in your language's main.str2 file, where MyLang is the name of your languages (as defined in spoofaxc.cfg:

rules // Analysis

  downgrade-placeholders = downgrade-placeholders-MyLang
  upgrade-placeholders   = upgrade-placeholders-MyLang
  is-inj                 = is-MyLang-inj-cons
  pp-partial             = pp-partial-MyLang-string
  pre-analyze            = explicate-injections-MyLang
  post-analyze           = implicate-injections-MyLang

In your Statix files, for each rule define a predicate that accepts a placeholder where a syntactic sort is permitted. For example:

rules // placeholders

  programOk(Module-Plhdr()).

  declOk(_, Decl-Plhdr()).

  typeOfExp(_, Exp-Plhdr()) = _.

Using Semantic Code Completion¶

In Eclipse, in a file of your language, type the placeholder somewhere where it is permitted. Unless overridden, the placeholder is a sort name within double square brackets, such as [[Exp]]. Then put the caret on the placeholder and press Cmd+Space on macOS (or Ctrl+Space on Linux/Windows) to invoke code completion.

In a future release the placeholder will not need to be input explicitly.

Limitations¶

For this first release of semantic code completion, there are some limitations:

You have to type the placeholder explicitly to invoke code completion.
If the file contains errors, code completion might fail to return results.

If you have catch-all predicates, code completion will not work. For example:

// This prevents code completion from finding completions:
typeOfExp(_, _) = _ :-
  try { false } | warning $[This expression is not yet implemented].

These limitations will be lifted in subsequent releases.