Launch HN: DeepSource (YC W20) – Find and fix issues during code reviews

We'll tweet about it at https://twitter.com/deepsourcehq

How is this different (or better?) than existing products that offer the same service, such as Codacy.

Have been a paying customer of Codacy’s for ~2 years and they support most languages out of the box at this point, with Git integration similar to your own.

Curious on your thoughts.

There's a better solution: use open-source cli tools that do just that!

1. 520 Python checks? Use `wemake-python-styleguide` (wrapper around flake8) that has bigger amount of checks: https://github.com/wemake-services/wemake-python-styleguide There's also `pylint` with a set of awesome checks as well.

2. Type checking? Use `mypy`: it just a single command!

3. Autofixing? Use `black` / `autopep8` / `autoflake` and you can use `pybetter` to have the same ~15 auto-fix rules. But, it is completely free and open-source

I don't like this whole idea of such tools (both technically and ethically):

- Why would anyone want to send all their codebase to 3rd party? We used to call it a security breach back in the days

- On moral side, this (and similar) projects look like thin wrappers around open-source tools but with a monetisation model. How much do these companies contribute back to the original authors of pylint, mypy, flake8? Ones who created and maintained them for years. I will be happy to be wrong here

So our CI pipelines are always set up so that failed linting means blocked merge capability. Your PR isn't ready for review if it's failing rubocop for example. Do you intend to integrate your tool into this type of workflow but by making the lint issues apparent via comment on the PR in GitHub vs in the CI?

> There's a better solution: use open-source cli tools that do just that!

We do not deny that you can't run the open-source tools locally. Be it one line command, or be it setting up pylint or flake8 with dedicated configurations. DeepSource is a tool meant to eliminate the need to set up all those open source tools locally or in your CI pipeline. So that you don't need to

- Fish for issues amongst hundreds of lines of logs in the CI

- Figure out and update linter config to remove duplicates and false positives (for ex: Bandit throws errors like `assets statement used` in a test file — which is a false-positive. Bandit doesn’t know that it is a test file by default)

- Some issues needed better description of why is that an issue, for ex: why should default file permissions be 0600? Justification on why is it necessary,.

- By default on every commit or pull request, linters run on all the files.

- If there are issues that occur in say 50 places, one have to manually fix it.

> 1. 520 Python checks? Use `wemake-python-styleguide` (wrapper around flake8) that has bigger amount of checks: https://github.com/wemake-services/wemake-python-styleguide There's also `pylint` with a set of awesome checks as well.

Our focus at the moment is not on style issues. In fact, amongst the categories of issues we raise (anti-patterns, bug-risks, performance, security, style, documentation), style issues are the most debated on by our users as it is really subjective. We’re thinking of removing style issues by default (as an opt-in) and are working on running formatters like `black`, `yapf`, .. with a single line config in `.deepsource.toml`. Our analyzer team actively adds custom rules which you don’t get from the open-source tools. The following issues for example:

- Raising another exception when `assert` fails is ineffective. For ex: `assert isinstance(num_channels, int), ValueError('Number of image channels needs to be an integer')`

- If the condition would not be satisfied, user would be expecting a `ValueError`, but this would be raised: `AssertionError: Number of image channels needs to be an integer` which should be

- `yield` used inside a comprehension (which breaks code in Python 3.8)

- Write operation on file that is opened in read-only mode

- I/O detected on a closed file descriptor

> 2. Type checking? Use `mypy`: it just a single command!

Sure. If one prefers running it locally (or) as part of their CI. But if you already use DeepSource to flag issues, it can be enabled by a single line in .deepsource.toml file.

> 3. Autofixing? Use `black` / `autopep8` / `autoflake` and you can use `pybetter` to have the same ~15 auto-fix rules. But, it is completely free and open-source

We are working on adding support for autopep8, black and autoflake in coming weeks. They mostly auto-patch stylistic issues [1]. Thanks for letting us know about pybetter. It looks like a great tool and fixes ~9 issues [2]. DeepSource’s autofix aim is to fix more than 3/4th of issues we detect and we detect 522 issues in our Python analyzer. We have dedicated engineering team actively working on the analyzers. As of today, following are some of the issues our Python analyzer can autofix (which I couldn’t find it among the open-source tools):

- No use of `self`

- Usafe of dangerous default argument

- Module imported but unused

- Function contains unused argument

- Debugger import detected

- Debugger activation detected

- Unnecessary comprehension

- Unnecessary literal

- Unnecessary call

- Unnecessary typecast

- Bad comparison test

- Empty module

- Built-in function `len` used as condition

- Unnecessary `fstring`

- `raise NotImplemented` should be `raise NotImplementedError`

- `assert` statement used outside of tests

Same goes with Go and other analyzers we support.

> I don't like this whole idea of such tools (both technically and ethically): > Why would anyone want to send all their codebase to 3rd party? We used to call it a security breach back in the days.

We follow strict security practices [3]. In a gist, 1) We do not store your code, 2) Source code is pulled in an isolated environment that has no access to any of our internal systems or the external network, 3) As soon as the analysis is completed, the environment is destroyed and all logs are purged. Also, there are many tools that developers use everyday (Travis CI, Circle CI, GitHub) where the source code is sent to the cloud — I don't think it is accurate to call it a security breach. That said, we have on-premise setup of DeepSource in the roadmap. We’re working on SOC 2 Type 2 compliance as well [4].

> On moral side, this (and similar) projects look like thin wrappers around open-source tools but with a monetisation model. How much do these companies contribute back to the original authors of pylint, mypy, flake8? Ones who created and maintained them for years. I will be happy to be wrong here

We have kept the tool completely free to use for open-source projects. We’ve also partnered with GitHub Education and made it free for students. We’re an early stage company trying to build a business in automating objective parts of code review and making it easier for every developer to adopt and use static analysis. With all transparency, we had plans to sponsor open-source projects but got sidetracked due to various reasons. We will be backing some of the open-source projects, in next couple of weeks.

[1] https://gist.githubusercontent.com/jaipradeesh/6ad8404fef253...

[2] https://gist.githubusercontent.com/jaipradeesh/b8a0e6b526f73...

[3] https://deepsource.io/security

[4] https://vanta.com/guides/vantas-guide-to-soc-2