Glass
A semantic search tool for Erlang that supports large code-bases.
Glass is a tool for semantically searching source code, currently focusing on Erlang. You can think of it as "grep, if grep could understand Erlang code".
Usage example
> glass:index(glass, "/path/to/glass").
> glass:search(glass, "maps:without([position], _)").
%% in glass_to_query/1 at ./_build/default/lib/glass_backend/ebin/glass_query.beam:25
30| maps:without([position], Attrs)
%% in minimal_attributes/1 at ./_build/default/lib/glass_backend/ebin/glass_query.beam:90
91| maps:without([position], Map)
For more examples and usage, please refer to the Docs.
Querying language
Glass uses a querying language based on pattern unification (and, in the future, possibly with more logical operators). In practice, this means that in order to query a codebase, you provide a piece of Erlang code that has variables where expressions can go.
The query:
maps:without([position], Arg)
Will match any maps:without call whose first argument is the exact list [position], and the second argument is any Erlang expression, which will be bound to Arg within this query.
Variables are unified, which means that, just like in regular Erlang pattern matching, you can use this to query pieces of code that have the same expression in different places. A query for the identity function is:
fun(A) -> A end
A query for taking the first element of a tuple would be:
fun({A, _}) -> A end
This provides a simple foundation for querying code that is at the same time very powerful. Particularly when extended for refactoring. A query like (syntax not final):
s/log(File, Format, [error])/log(error_log, Format ++ " file: ~p", [error, File])/
Could transform a piece of code like:
log(debug, "Failed, reason=~p", [error])
Into:
log(error_log, "Failed, reason=~p" ++ "file: ~p", [error, debug])
Development setup
Glass requires both OTP21+ and rebar3. rebar3 shell from the root will drop you into an Erlang shell for Glass.
Roadmap
The current focus is on making the query language feature-complete. And we have plans to work on optimisation, refactoring, and more advanced (incremental) static analysis in the future.
See our roadmap document for more details.
How to contribute
See our guide on contributing.
Release History
See our changelog.
License
Copyright ยฉ 2020 Klarna Bank AB
For license details, see the LICENSE file in the root of this project.
