Piping source ignores excluded_paths configuration

[stevenharman]

I am working on the Reek + Ale integration which will pipe the source and pass the --stdin-filename argument. I noticed Reek was ignoring my configured exclude_paths and so errors were being reported via Ale. I tried passing the --force-exclusion flag, but that didn't change anything. I then confirmed all of this by calling reek in a similar manner. An example:

---
# Directories below will not be scanned at all
exclude_paths:
  - db/migrate

Piping to reek, with flags:

$ cat db/migrate/20181015212457_create_foos.rb | reek --config .reek.yml --force-exclusion  --stdin-filename 'db/migrate/20181015212457_create_foos.rb'
db/migrate/20181015212457_create_foos.rb -- 3 warnings:
  [6, 7, 8, 9, 11]:FeatureEnvy: CreateFoos#change refers to 't' more than self (maybe move it to another class?) [https://github.com/troessner/reek/blob/v5.1.0/docs/Feature-Envy.md]
  [4]:TooManyStatements: CreateFoos#change has approx 9 statements [https://github.com/troessner/reek/blob/v5.1.0/docs/Too-Many-Statements.md]
  [5]:UncommunicativeVariableName: CreateFoos#change has the variable name 't' [https://github.com/troessner/reek/blob/v5.1.0/docs/Uncommunicative-Variable-Name.md]

I would have expected Reek to ignore this file, per the configuration.

I started digging into Reek and it looks like Reek::CLI::Application#source_from_pipe directly loads the code, rather than using SourceLocator to filter out source files based on the excluded_paths configuration.

reek/lib/reek/cli/application.rb

Lines 116 to 118 in add8959

	def source_from_pipe
	[Source::SourceCode.from($stdin, origin: options.stdin_filename)]
	end

I wonder if there's a way to either leverage, or exact, the bits of Source::SourceLocator which determine if we should exclude a source file. If so, we could check if stdin_filename is set, and if so, check if the file is excluded.

Thoughts or suggestions? I'd be happy to get a PR going, given a little guidance on a preferred approach.

Thank you!

See also: #1343 (comment)

[mvz]

Hi @stevenharman, thank you for this detailed bug report. This combination of flags should indeed have the effect you expected.

Extracting the exclusion logic from SourceLocator sounds like a good approach, so if you'd like to take a stab at a PR, that would be much appreciated.