Presenting pre-commit-go

---

---

# pre-commit-go

(in 6 minutes or less)

---

# Genesis

&nbsp;

- Want to run tests all the time because I'm a lousy coder

- Good at Design but make lots of typos

- I'm also impatient so I want it to be *smart* and *fast*

- `pcg` is quick to type

---

# Goals

&nbsp;

## Correct

## Versatile

## Simple

## Safe
]

---

# Dependency DAG analysis

```
$GOPATH/src/github.com/$USER/foo/

- cmd/foo
- pkg/a
- pkg/b
- pkg/c
- pkg/d
- pkg/e
```

You touch `pkg/b/doc.go`. What is tested?

---

# Dependency DAG analysis

```
$GOPATH/src/github.com/$USER/foo/

- cmd/foo  imports pkg/a and pkg/e
- pkg/a    imports pkg/b
- pkg/b    imports pkg/c and pkg/e
- pkg/c    imports pkg/d
- pkg/d    imports pkg/e
- pkg/e
```

You touch `pkg/b/doc.go`. What is tested?

---

# Dependency DAG analysis

```
$GOPATH/src/github.com/$USER/foo/

- cmd/foo  imports pkg/a and pkg/e
- pkg/a    imports pkg/b
- pkg/b    imports pkg/c and pkg/e
- pkg/c    imports pkg/d
- pkg/d    imports pkg/e
- pkg/e
```

You touch `pkg/b/doc.go`. What is tested?

If you use `go test ./...` the answer is

---

# Dependency DAG analysis

```
$GOPATH/src/github.com/$USER/foo/

- cmd/foo  imports pkg/a and pkg/e
- pkg/a    imports pkg/b
- pkg/b    imports pkg/c and pkg/e
- pkg/c    imports pkg/d
- pkg/d    imports pkg/e
- pkg/e
```

You touch `pkg/b/doc.go`. What is tested?

With `pcg`

- Packages tested: `cmd/foo`, `pkg/a` and `pkg/b`
  - `pkg/c`, `pkg/d` and `pkg/e` are left alone

---

# Native checks (packages)

### build
  - Builds only test-less packages

### coverage
  - Enforces minimum coverage per package
  - Supports global inference! (*explained later*)

### test
  - Runs `go test` in parallel
  - Supports optional flags like `-short` or `-race`

---

# Native checks (files)

### copyright
  - Enforces copyright header on sources, e.g.:

```
// Copyright 2015 The Foo Authors. All rights reserved.
// Use of this source code is governed by a WTFPL-style
// license that can be found in the LICENSE file.
```

### gofmt
  - Enforces [gofmt -s](https://golang.org/cmd/gofmt/)

### goimports
  - Enforces [goimports](https://golang.org/x/tools/cmd/goimports)

---

# Native checks (linters)

### errcheck

- Uses [errcheck](https://github.com/kisielk/errcheck) linter (I like this one)

### golint

- Use [golint](https://github.com/golang/lint/golint) linter
  - Supports blacklisting messages

### govet

- Use [go tool vet](https://golang.org/x/tools/cmd/vet) linter
  - Supports blacklisting messages

---

# Custom checks

&nbsp;

`pcg` will soon support custom `go get`'able checks  
(still incomplete)

Extensibility built-in

---

# Checks

### Smart

Checks are either *package level* or *file level*:

- `gofmt` is file level
  - `test` is package level

### DAG analysis

Differentiate between modified packages and transitive dependencies

- `test` runs on all transitive dependencies
  - `errcheck` runs only on modified packages

---

# Checks

### Contextual

The same check has different behavior depending on mode:

*On commit*: `go test -short`

*On push*: `go test -race`

&nbsp;

### Designed to be fast in the common flow

---

# Runs automatically

&nbsp;

Upon execution, `pcg` sets itself as:
  - .git/hooks/pre-commit
  - .git/hooks/pre-push

so it is run automatically afterward.

Viral design, trivial installation.

---

## Acts on change (Δ), not repo

### git commit
  - Δ of what is in the git staging index
  - *Automatically stash if needed*
  - Tests must be fast: default hard limit 2 seconds
  - Uses `-short` by default

### git push
  - Δ between code being pushed and upstream
  - Slower tests; default hard limit 15 seconds
  - Uses `-race` instead of `-short`

---

# Continuous Integration

### On CI
  - All checks on all files, and more checks if desired
  - CI mode if environment variable `CI=true` is set
    - Defined on all popular hosted CI systems

&nbsp;

Review of hosted CI systems supporting Go:

[maruel.ca/post/ci-go-review/](https://maruel.ca/post/ci-go-review/)

---

# Executed manually

### Running `pcg` manually
Δ between local and tracked branch, runs same tests as *on push*

&nbsp;

### Running a mode manually

`pcg run -m lint` runs non-default linter checks, only on relevant code

Use `pcg run -m lint -a` to run on all code

---

# Configuration file

`pre-commit-go.yml`

### Location

- Checkout's root
  - Hidden in `.git/`
  - User global settings in `~/.config/`

### Properties

- Defines what checks are enabled in each mode
  - Not required, `pcg` aims for sane defaults
  - `pcg writeconfig` generates the defaults
  - Can be used to force version upgrade

---

# Extra slides

If used less than 6 minutes,  
there's other great tools to talk about!

---

# panicparse

&nbsp;

*Crash your app in style*

---

# Turns this

goroutine 11 [running]:
github.com/luci/luci-go/client/archiver.(*archiver).PushFile(0xc208032410, 0xc20968a3c0, 0x5b, 0xc20988c280, 0x7d, 0x0, 0x0)
  /gopath/src/github.com/luci/luci-go/client/archiver/archiver.go:325 +0x2c4
github.com/luci/luci-go/client/isolate.archive(0x7fbdab7a5218, 0xc208032410, 0xc20803b0b0, 0x22, 0xc208046370, 0xc20804666a, 0x17, 0x0, 0x0, 0x0, ...)
  /gopath/src/github.com/luci/luci-go/client/isolate/isolate.go:148 +0x12d2
github.com/luci/luci-go/client/isolate.Archive(0x7fbdab7a5218, 0xc208032410, 0xc20803b0b0, 0x22, 0xc208046370, 0x0, 0x0)
  /gopath/src/github.com/luci/luci-go/client/isolate/isolate.go:102 +0xc9
main.func·004(0x7fffc3b8f13a, 0x2c)
  /gopath/src/github.com/luci/luci-go/client/cmd/isolate/batch_archive.go:166 +0x7cd
created by main.(*batchArchiveRun).main
  /gopath/src/github.com/luci/luci-go/client/cmd/isolate/batch_archive.go:167 +0x42c

goroutine 1 [chan receive]:
main.(*batchArchiveRun).main(0xc2080300b0, 0x7fbdab7a50b8, 0x9979a0, 0xc20800a070, 0x3, 0x3, 0x0, 0x0)
  /gopath/src/github.com/luci/luci-go/client/cmd/isolate/batch_archive.go:175 +0x54c
main.(*batchArchiveRun).Run(0xc2080300b0, 0x7fbdab7a50b8, 0x9979a0, 0xc20800a070, 0x3, 0x3, 0xc208038010)
  /gopath/src/github.com/luci/luci-go/client/cmd/isolate/batch_archive.go:203 +0x28d
github.com/maruel/subcommands.Run(0x7fbdab7a50b8, 0x9979a0, 0xc20800a010, 0x9, 0x9, 0x43d185)
  /gopath/src/github.com/maruel/subcommands/subcommands.go:262 +0x405
main.main()
  /gopath/src/github.com/luci/luci-go/client/cmd/isolate/main.go:28 +0x70

goroutine 5 [syscall]:
os/signal.loop()
  /golang/src/os/signal/signal_unix.go:21 +0x1f
created by os/signal.init·1
  /golang/src/os/signal/signal_unix.go:27 +0x35
```
]

---

# Into this

![screenshot](https://raw.githubusercontent.com/wiki/maruel/panicparse/screenshot3.png)

---

# Try it out:

&nbsp;

*Crash your app in style*

&nbsp;

```
go get github.com/maruel/panicparse/cmd/pp

echo -e 'package main\nfunc main() {panic("!")}' > c.go

go run c.go |& pp
```

---

# covg

*Coverage, fast, global*

---

# Standalone global inference coverage

Running test on a package contributes coverage on all imported
packages.

Gives broader picture of coverage scenario, permits focusing on actually
untested corner cases.

E.g. unit tests in package `foo/bar` will contribute coverage in `foo/goo` when
unit tests calls out in this package.

---

# webskel

*Hugo based framework*

---

# Hugo based framework

Includes:

- Static ordered pages and generated NavBar
  - Blog
  - [remarkjs.com](https://remarkjs.com) based presentation
    - This presentation is using this
  - Metadata: Twitter, Facebook, Google & Bing
  - Instructions for:
    - [cloudflare.com](https://cloudflare.com) https fronting
    - github page generated via [codeship.com](https://codeship.com)

Powers https://maruel.ca

---

# Other Go projects

---

# Other Go projects

[maruel.ca/page/projects/](https://maruel.ca/page/projects/)

- Circular buffer (in-memory log serving over HTTP)
- FLIR lepton IR camera driver code serves images over websocket
- subcommands for automatic typo correction
- serve-dir to quickly serve a directory
- Isolate: Content addressed cache (used in Chromium infrastructure, does >120
  million lookups per day)
- Reed-Solomon error correction
- Fortuna PRNG