View Source Credo.Check.Consistency.Collector behaviour (Credo v1.7.2-rc.4)
A behavior for modules that walk through source files and identify consistency issues.
When defining a consistency check, you would typically use this structure for the main module, responsible for formatting issue messages:
defmodule Credo.Check.Consistency.SomeCheck do
use Credo.Check, run_on_all: true
@collector Credo.Check.Consistency.SomeCheck.Collector
def run(source_files, exec, params) when is_list(source_files) do
issue_formatter = &issues_for/3
@collector.find_and_append_issues(source_files, exec, params, issue_formatter)
end
defp issues_for(expected, source_file, params) do
issue_meta = IssueMeta.for(source_file, params)
issue_locations =
@collector.find_locations_not_matching(expected, source_file)
Enum.map(issue_locations, fn(location) ->
format_issue issue_meta, message: ... # write an issue message
end)
endThe actual analysis would be performed by another module
implementing the Credo.Check.Consistency.Collector behavior:
defmodule Credo.Check.Consistency.SomeCheck.Collector do
use Credo.Check.Consistency.Collector
def collect_matches(source_file, params) do
# ...
end
def find_locations_not_matching(expected, source_file) do
# ...
end
endRead further for more information on collect_matches/2,
find_locations_not_matching/2, and issue_formatter.
Summary
Callbacks
When you call @collector.find_and_append_issues/4 inside the check module,
the collector first counts the occurrences of different matches
(e.g. :with_space and :without_space for a space around operators check)
per each source file.
issue_formatter may call the @collector.find_locations_not_matching/2
function to obtain additional metadata for each occurrence of
an unexpected match in a given file.
Types
@type issue_formatter() :: (term(), Credo.SourceFile.t(), Keyword.t() -> [Credo.Issue.t()])
Callbacks
@callback collect_matches( source_file :: Credo.SourceFile.t(), params :: Keyword.t() ) :: %{required(term()) => non_neg_integer()}
When you call @collector.find_and_append_issues/4 inside the check module,
the collector first counts the occurrences of different matches
(e.g. :with_space and :without_space for a space around operators check)
per each source file.
collect_matches/2 produces a map of matches as keys and their frequencies
as values (e.g. %{with_space: 50, without_space: 40}).
The maps for individual source files are then merged, producing a map that reflects frequency trends for the whole codebase.
@callback find_locations_not_matching( expected :: term(), source_file :: Credo.SourceFile.t() ) :: [term()]
issue_formatter may call the @collector.find_locations_not_matching/2
function to obtain additional metadata for each occurrence of
an unexpected match in a given file.
An example implementation that returns a list of line numbers on which unexpected occurrences were found:
def find_locations_not_matching(expected, source_file) do
traverse(source_file, fn(match, line_no, acc) ->
if match != expected do
acc ++ [line_no]
else
acc
end
end)
end
defp traverse(source_file, fun), do: ...