Searcher

The language auto-completion feature requires an ability to search the codebase using different search criteria. This document describes the Searcher module, which consists of the suggestions database and the ranking algorithm for ordering the results.

Suggestions Database
Results Ranking

Suggestions Database

Suggestions database holds entries for fulfilling the auto-completion requests with additional indexes used to answer the different search criteria. The database is populated partially by analyzing the sources and enriched with the extra information from the runtime.

API data types for the suggestions database are specified in the Language Server Message Specification document.

Database Structure

Implementation utilizes the SQLite database.

Database is created per project and the database file stored in the project directory. That way the index can be preserved between the IDE restarts.

Suggestions Table

id INTEGER - unique identifier
kind INTEGER - type of suggestion entry, i.e. Atom, Method, Function, or Local
name TEXT - entry name
self_type TEXT - self type of the Method
return_type TEXT - return type of the entry
documentation TEXT - documentation string

Arguments Table

id INTEGER - unique identifier
suggestion_id INTEGER - suggestion key this argument relates to
name TEXT - argument name
type TEXT - argument type; const 'Any' is used to specify generic types
is_suspended INTEGER - indicates whether the argument is lazy
has_defult INTEGER - indicates whether the argument has default value
default_value TEXT - optional default value

Static Analysis

The database is filled by analyzing the Intermediate Representation (IR) parsed from the source.

Language constructs for suggestions database extracted from the IR:

Atoms
Methods
Functions
Local assignments
Documentation

In addition, it holds the locality information for each entry. Locality information specifies the scope where the node was defined, which is used in the results ranking algorithm.

Runtime Inspection

The IR is missing information about the types. Runtime instrumentation is used to capture the types and refine the database entries.

Information for suggestions database gathered in runtime:

Types

Search Indexes

The database allows searching the entries by the following criteria, applying the ranking algorithm:

name
type
documentation text
documentation tags

Results Ranking

The search result has an intrinsic ranking based on the scope and the type.

Scope

The results from the local scope have the highest rank in the search result. As the scope becomes wider, the rank decreases.

const_x = 42

main =
    x1 = 0
    foo x =
        x2 = x + 1
        calculate #

For example, when completing the argument of calculate: Number -> Number function, the search results will have the order of: x2 > x1 > const_x.

Type

Suggestions based on the type are selected by matching with the string runtime type representation.

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