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Add code styleguide split into general, Go, JS, and Python files

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# sneak/styleguide
The following is the first released version of my personal code styleguide.
There are many like it, but this one is mine.
Only the Go portion is "complete". The others are mostly just placeholders.
Feedback and suggestions are not only welcome but explicitly encouraged.
[sneak@sneak.berlin](mailto:sneak@sneak.berlin)
# My 2024 Code Styleguide
## All
1. Every project/repo should have a `Makefile` in the root. At a minimum,
`make clean`, `make run`, `make fmt`, and `make test` should work. Choose a
sane default target (`test` for libraries, `run` or `publish` for binaries).
`fmt` should invoke the appropriate formatters for the files in the repo,
such as `go fmt`, `prettier`, `black`, etc. Other standard `Makefile` targets
include `deploy`, `lint`. Consider the `Makefile` the official documentation
about how to operate the repository.
1. If it's possible to write a `Dockerfile`, include at least a simple one. It
should be possible to build and run the project with `docker build .`.
1. For F/OSS-licensed software, try to include the full source code of the
current version (and any dependencies, such as vendored dependencies) in the
docker image. They're small and should be included with the binary.
1. Under no circumstances should any credentials or secrets ever be committed to
any repository, even private ones. Store secrets in environment variables,
and if they are absolutely required, check on startup to make sure they are
set/non-default and complain loudly if not. Exception, sometimes: public
keys. (Public keys can still sometimes be secrets for operational security
reasons.)
1. Avoid nesting `if` statements. If you have more than one level of nesting,
consider inverting the condition and using `return` to exit early.
1. Almost all services/servers should accept their configuration via environment
variables. Only go full config file if absolutely necessary.
1. For services/servers, log JSON to stdout. This makes it easier to parse and
aggregate logs when run under `docker`. Use structured logging whenever
possible. You may detect if the output is a terminal and pretty-print the
logs in that case.
1. Debug mode is enabled by setting the environment variable `DEBUG` to a
non-empty string. This should enable verbose logging and such. It will never
be enabled in prod.
1. For services/servers, make a healthcheck available at
`/.well-known/healthcheck`. This is out of spec but it is my personal
standard. This should return a 200 OK if the service is healthy, along with a
JSON object containing the service's name, uptime, and any other relevant
information, and a key of "status" with a value of "ok" if the service is
healthy. Make sure that in the event of a failure, the service returns a 5xx
status code for that route.
1. If possible, for services/servers, include a /metrics endpoint that returns
Prometheus-formatted metrics. This is not required for all services, but is a
nice-to-have.
## Bash / Shell
1. Use `[[` instead of `[` for conditionals. It's a shell builtin and doesn't
have to execute a separate process.
1. Use `$( )` instead of backticks. It's easier to read and nest.
1. Use `#!/usr/bin/env bash` as the shebang line. This allows the script to be
run on systems where `bash` is not in `/bin`.
1. Use `set -euo pipefail` at the top of every script. This will cause the
script to exit if any command fails, and will cause the script to exit if any
variable is used before it is set.
1. Use `pv` for progress bars when piping data through a command. This makes it
easier to see how much data has been processed.
1. Put all code in functions, even a main function. Define all functions then
call main at the bottom of the file.
## Docker Containers (for services)
1. Use `runit` with `runsvinit` as the entrypoint for all containers. This
allows for easy service management and logging. In startup scripts
(`/etc/service/*/run`) in the container, put a `sleep 1` at the top of the
script to avoid spiking the cpu in the case of a fast-exiting process (such
as in an error condition). This also limits the maximum number of error
messages in logs to 86400/day.
# Author
[@sneak](https://sneak.berlin)
<[sneak@sneak.berlin](mailto:sneak@sneak.berlin)>
# License
MIT. See [LICENSE](../LICENSE).

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# Golang
1. Try to hard wrap long lines at 77 characters or less.
1. Don't commit anything that hasn't been `go fmt`'d. The only exception is
when committing things that aren't yet syntactically valid, which should
only happen pre-v0.0.1 or on a non-`main` branch.
1. Even if you are planning to deal with only positive integers, use
`int`/`int64` types instead of `uint`/`uint64` types. This is for
consistency and compatibility with the standard library; it's better than
casting all the time.
1. Any project that has more than 2 or 3 modules should use the
`go.uber.org/fx` dependency injection framework to keep things tidy.
1. If you have to choose between readable and clever, opt for readable. It's ok
to make the code less concise or slightly less idiomatic if you can keep it
dead simple.
1. Embed the git commit hash into the binary and include it in startup logs and
in health check output. This is to make it easier to correlate running
instances with their code. Do not include build time or build user, as these
will make the build nondeterministic.
Example relevant Makefile sections:
Given a `main.go` like:
```go
package main
import (
"fmt"
)
var (
Version string
Buildarch string
)
func main() {
fmt.Printf("Version: %s\n", Version)
fmt.Printf("Buildarch: %s\n", Buildarch)
}
```
```make
VERSION := $(shell git describe --always --dirty)
BUILDARCH := $(shell uname -m)
GOLDFLAGS += -X main.Version=$(VERSION)
GOLDFLAGS += -X main.Buildarch=$(BUILDARCH)
# osx can't statically link apparently?!
ifeq ($(UNAME_S),Darwin)
GOFLAGS := -ldflags "$(GOLDFLAGS)"
endif
ifneq ($(UNAME_S),Darwin)
GOFLAGS = -ldflags "-linkmode external -extldflags -static $(GOLDFLAGS)"
endif
./httpd: ./pkg/*/*.go ./internal/*/*.go cmd/httpd/*.go
go build -o $@ $(GOFLAGS) ./cmd/httpd/*.go
```
1. Avoid obvious footguns. For example, use range instead of for loops for
iterating.
1. Try to use zerolog for logging. It's fast and has a nice API. For
smaller/quick projects, the standard library's `log` package (and
specifically `log/slog`) is fine. In that case, log structured logs whenever
possible, and import `sneak.berlin/go/simplelog` to configure it
appropriately. Example:
```go
package main
import (
"log/slog"
_ "sneak.berlin/go/simplelog"
)
func main() {
slog.Info("Starting up")
}
```
1. Commit at least a single test file to check compilation. The test file can
be empty, but it should exist. This is to ensure that `go test ./...` will
always function as a syntax check at a minimum.
1. Full TDD and coverage isn't that important, but when fixing a specific bug,
try to write a test that reproduces the bug before fixing it. This will help
ensure that the bug doesn't come back later, and crystallizes the experience
of discovering the bug and the resulting fix into the repository's history.
1. For anything beyond a simple script or tool, or anything that is going to
run in any sort of "production" anywhere, make sure it passes
`golangci-lint`.
1. Write a `Dockerfile` for every repo, even if it only runs the tests and
linting. `docker build .` should always make sure that the code is in an
able-to-be-compiled state, linted, and any tests run. The Docker build
should fail if linting doesn't pass.
1. Include a `Makefile` with targets for at least `clean` and `test`. If there
are multiple binaries, include a target for each binary. If there are
multiple binaries, include a target for `all` that builds all binaries.
1. If you are writing a single-module library, `.go` files are okay in the repo
root.
1. If you are writing a multi-module project, put all `.go` files in a `pkg/`
or `internal/` subdirectory. `internal/` is for modules used only by the
current repo, and `pkg/` is for modules that can be consumed externally.
This is to keep the repo root as clean as possible.
1. Binaries go in `cmd/` directories. Each binary should have its own
directory. This is to keep the root clean and to make it easier to see what
is a library and what is a binary. Only package `main` files should be in
`cmd/*` directories.
1. Keep the `main()` function as small as possible.
1. Keep the `main` package as small as possible. Move as much code as is
feasible to a library package, even if it's an internal one. `main` is just
an entrypoint to your code, not a place for implementations. Exception:
single-file scripts.
1. HTTP HandleFuncs should be returned from methods or functions that need to
handle HTTP requests. Don't use methods or our top level functions as
handlers.
1. Provide a .gitignore file that ignores at least `*.log`, `*.out`, and
`*.test` files, as well as any binaries.
1. Constructors should be called `New()` whenever possible. `modulename.New()`
works great if you name the packages properly.
1. Don't make packages too big. Break them up.
1. Don't make functions or methods too big. Break them up.
1. Use descriptive names for functions and methods. Don't be afraid to make
them a bit long.
1. Use descriptive names for modules and filenames. Avoid generic names like
`server`. `util` is banned.
1. Constructors should take a Params struct if they need more than 1-2
arguments. Positional arguments are an endless source of bugs and should be
avoided whenever possible.
1. Use `context.Context` for all functions that need it. If you don't need it,
you can pass `context.Background()`. Anything long-running should get and
abide by a Context. A context does not count against your number of function
or method arguments for purposes of calculating whether or not you need a
Params struct, because the `ctx` is always first.
1. Contexts are always named `ctx`.
1. Use `context.WithTimeout` or `context.WithDeadline` for any function that
could potentially run for a long time. This is especially true for any
function that makes a network call. Sane timeouts are essential.
1. If a structure/type is only used in one function or method, define it there.
If it's used in more than one, define it in the package. Keep it close to
its usages. For example:
```go
func (m *Mothership) tvPost() http.HandlerFunc {
type MSTVRequest struct {
URL string `json:"URL"`
}
type MSTVResponse struct {
}
return func(w http.ResponseWriter, r *http.Request) {
// parse json from request
var reqParsed MSTVRequest
err = json.NewDecoder(r.Body).Decode(&reqParsed)
...
if err != nil {
SendErrorResponse(w, MSGenericError)
return
}
log.Info().Msgf("Casting to %s: %s", tvName, streamURL)
SendSuccessResponse(w, &MSTVResponse{})
}
}
```
1. Avoid global state, especially global variables. If you need to store state
that is global to your launch or application instance, use a package
`globals` or `appstate` with a struct and a constructor and require it as a
dependency in your constructors. This will allow consumers to be more easily
testable and will make it easier to reason about the state of your
application. Alternately, if your dependency graph allows for it, put it in
the main struct/object of your application, but remember that this harms
testability.
1. Package-global "variables" are ok if they are constants, such as static
strings or integers or errors.
1. Whenever possible, avoid hardcoding numbers or values in your code. Use
descriptively-named constants instead. Recall the famous SICP quote:
"Programs must be written for people to read, and only incidentally for
machines to execute." Rather than comments, a descriptive constant name is
much cleaner.
Example:
```go
const jsonContentType = "application/json; charset=utf-8"
func (s *Handlers) respondJSON(w http.ResponseWriter, r *http.Request, data interface{}, status int) {
w.WriteHeader(status)
w.Header().Set("Content-Type", jsonContentType)
...
}
```
1. Define your struct types near their constructors.
1. Define your interface types near the functions that use them, or if you have
multiple conformant types, put the interface(s) in their own file.
1. Define errors as package-level variables. Use a descriptive name for the
error. Use `errors.New` to create the error. If you need to include
additional information in the error, use a struct that implements the
`error` interface.
1. Use lowerCamelCase for local function/variable names. Use UpperCamelCase for
type names, and exported function/variable names. Use snake_case for JSON
keys. Use lowercase for filenames.
1. Explicitly specify UTC for datetimes unless you have a very good reason not
to. Use `time.Now().UTC()` to get the current time in UTC.
1. String dates should always be ISO8601 formatted. Use `time.Time.Format` with
`time.RFC3339` to get the correct format.
1. Use `time.Time` for all date and time values. Do not use `int64` or `string`
for dates or times internally.
1. When using `time.Time` in a struct, use a pointer to `time.Time` so that you
can differentiate between a zero value and a null value.
1. Use `time.Duration` for all time durations. Do not use `int64` or `string`
for durations internally.
1. When using `time.Duration` in a struct, use a pointer to `time.Duration` so
that you can differentiate between a zero value and a null value.
1. Whenever possible, in argument types and return types, try to use standard
library interfaces instead of concrete types. For example, use `io.Reader`
instead of `*os.File`. Tailor these to the needs of the specific function or
method. Examples:
- **`io.Reader`** instead of `*os.File`:
- `io.Reader` is a common interface for reading data, which can be
implemented by many types, including `*os.File`, `bytes.Buffer`,
`strings.Reader`, and network connections like `net.Conn`.
- **`io.Writer`** instead of `*os.File` or `*bytes.Buffer`:
- `io.Writer` is used for writing data. It can be implemented by
`*os.File`, `bytes.Buffer`, `net.Conn`, and more.
- **`io.ReadWriter`** instead of `*os.File`:
- `io.ReadWriter` combines `io.Reader` and `io.Writer`. It is often used
for types that can both read and write, such as `*os.File` and
`net.Conn`.
- **`io.Closer`** instead of `*os.File` or `*net.Conn`:
- `io.Closer` is used for types that need to be closed, including
`*os.File`, `net.Conn`, and other resources that require cleanup.
- **`io.ReadCloser`** instead of `*os.File` or `http.Response.Body`:
- `io.ReadCloser` combines `io.Reader` and `io.Closer`, and is commonly
used for types like `*os.File` and `http.Response.Body`.
- **`io.WriteCloser`** instead of `*os.File` or `*gzip.Writer`:
- `io.WriteCloser` combines `io.Writer` and `io.Closer`. It is used for
types like `*os.File` and `gzip.Writer`.
- **`io.ReadWriteCloser`** instead of `*os.File` or `*net.TCPConn`:
- `io.ReadWriteCloser` combines `io.Reader`, `io.Writer`, and
`io.Closer`. Examples include `*os.File` and `net.TCPConn`.
- **`fmt.Stringer`** instead of implementing a custom `String` method:
- `fmt.Stringer` is an interface for types that can convert themselves
to a string. Any type that implements the `String() string` method
satisfies this interface.
- **`error`** instead of custom error types:
- The `error` interface is used for representing errors. Instead of
defining custom error types, you can use the `errors.New` function or
the `fmt.Errorf` function to create errors.
- **`net.Conn`** instead of `*net.TCPConn` or `*net.UDPConn`:
- `net.Conn` is a generic network connection interface that can be
implemented by TCP, UDP, and other types of network connections.
- **`http.Handler`** instead of custom HTTP handlers:
- `http.Handler` is an interface for handling HTTP requests. Instead of
creating custom handler types, you can use types that implement the
`ServeHTTP(http.ResponseWriter, *http.Request)` method.
- **`http.HandlerFunc`** instead of creating a new type:
- `http.HandlerFunc` is a type that allows you to use functions as HTTP
handlers by implementing the `http.Handler` interface.
- **`encoding.BinaryMarshaler` and `encoding.BinaryUnmarshaler`** instead of
custom marshal/unmarshal methods:
- These interfaces are used for binary serialization and
deserialization. Implementing these interfaces allows types to be
encoded and decoded in a standard way.
- **`encoding.TextMarshaler` and `encoding.TextUnmarshaler`** instead of
custom text marshal/unmarshal methods:
- These interfaces are used for text-based serialization and
deserialization. They are useful for types that need to be represented
as text.
- **`sort.Interface`** instead of custom sorting logic:
- `sort.Interface` is an interface for sorting collections. By
implementing the `Len`, `Less`, and `Swap` methods, you can sort any
collection using the `sort.Sort` function.
- **`flag.Value`** instead of custom flag parsing:
- `flag.Value` is an interface for defining custom command-line flags.
Implementing the `String` and `Set` methods allows you to use custom
types with the `flag` package.
1. Avoid using `panic` in library code. Instead, return errors to allow the
caller to handle them. Reserve `panic` for truly exceptional conditions.
1. Use `defer` to ensure resources are properly cleaned up, such as closing
files or network connections. Place `defer` statements immediately after
resource acquisition.
1. When calling a function with `go`, wrap the function call in an anonymous
function to ensure it runs in the new goroutine context:
Right:
```go
go func() {
someFunction(arg1, arg2)
}()
```
Wrong:
```go
go someFunction(arg1, arg2)
```
1. Use `iota` to define enumerations in a type-safe way. This ensures that the
constants are properly grouped and reduces the risk of errors.
Example:
```go
type HandScore int
const (
ScoreHighCard = HandScore(iota * 100_000_000_000)
ScorePair
ScoreTwoPair
ScoreThreeOfAKind
ScoreStraight
ScoreFlush
ScoreFullHouse
ScoreFourOfAKind
ScoreStraightFlush
ScoreRoyalFlush
)
```
Example 2:
```go
type ByteSize float64
const (
_ = iota // ignore first value by assigning to blank identifier
KB ByteSize = 1 << (10 * iota)
MB
GB
TB
PB
EB
ZB
YB
)
```
1. Don't hardcode big lists of things in your normal code. Either isolate lists
in their own module/package and write some getters, or use a third party
library. For example, if you need a list of country codes, you can use
[https://github.com/emvi/iso-639-1](https://github.com/emvi/iso-639-1). It's
okay to embed a data file (use `go embed`) in your binary if you need to,
but make sure you parse it once as a singleton and don't read it from disk
every time you need it. Don't use too much memory for this, embedding
anything more than perhaps 25MiB (uncompressed) is probably too much.
Compress the file before embedding and uncompress during the reading/parsing
step for efficiency.
1. When storing numeric values that represent a number of units, either include
the unit in the variable name (e.g. `uptimeSeconds`, `delayMsec`,
`coreTemperatureCelsius`), or use a type alias (that includes the unit
name), or use a 3p library such as
[github.com/alecthomas/units](https://github.com/alecthomas/units) for
SI/IEC byte units, or
[github.com/bcicen/go-units](https://github.com/bcicen/go-units) for
temperatures (and others). The type system is your friend, use it.
1. Once you have a working program, run `go mod tidy` to clean up your `go.mod`
and `go.sum` files. Tag a v0.0.1 or v1.0.0. Push your `main` branch and
tag(s). Subsequent work should happen on branches so that `main` is "always
releasable". "Releasable" in this context means that it builds and functions
as expected, and that all tests and linting passes.
## Other Golang Tips and Best Practices (Optional)
1. For any internet-facing http server, set appropriate timeouts and limits to
protect against slowloris attacks or huge uploads that can consume server
resources even without authentication.
Example to limit request body size:
```go
package main
import (
"fmt"
"net/http"
)
func main() {
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
// Limit the request body to 10MB
r.Body = http.MaxBytesReader(w, r.Body, 10<<20)
if err := r.ParseForm(); err != nil {
http.Error(w, "Request body too large", http.StatusRequestEntityTooLarge)
return
}
fmt.Fprintf(w, "Hello, World!")
})
http.ListenAndServe(":8080", nil)
}
```
Example to set appropriate timeouts:
```go
package main
import (
"net/http"
"time"
)
func main() {
server := &http.Server{
Addr: ":8080",
ReadTimeout: 5 * time.Second,
WriteTimeout: 10 * time.Second,
Handler: http.DefaultServeMux,
}
http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintf(w, "Hello, World!")
})
server.ListenAndServe()
}
```
1. When passing channels to goroutines, use read-only (`<-chan`) or write-only
(`chan<-`) channels to communicate the direction of data flow clearly.
1. Use `io.MultiReader` to concatenate multiple readers and `io.MultiWriter` to
duplicate writes to multiple writers. This can simplify the handling of
multiple data sources or destinations.
1. For simple counters and flags, use the `sync/atomic` package to avoid the
overhead of mutexes.
1. When using mutexes, minimize the scope of locking to reduce contention and
potential deadlocks. Prefer to lock only the critical sections of code. Try
to encapsulate the critical section in its own function or method. Acquire
the lock as the first line of the function, defer release of the lock as the
second line of the function, and lines 3-5 should perform the task. Try to
keep it as short as possible. Avoid using mutexes in the middle of a
function. In short, build atomic functions.
1. Design types to be immutable where possible. This can help avoid issues with
concurrent access and make the code easier to reason about.
1. Global state can lead to unpredictable behavior and makes the code harder to
test. Use dependency injection to manage state.
1. Avoid using `init` functions unless absolutely necessary as they can lead to
unpredictable initialization order and make the code harder to understand.
1. Provide comments for all public interfaces explaining what they do and how
they should be used. This helps other developers understand the intended use.
1. Be mindful of resource leaks when using `time.Timer` and `time.Ticker`.
Always stop them when they are no longer needed.
1. Use `sync.Pool` to manage a pool of reusable objects, which can help reduce
GC overhead and improve performance in high-throughput scenarios.
1. Avoid using large buffer sizes for channels. Unbounded channels can lead to
memory leaks. Use appropriate buffer sizes based on the application's needs.
1. Always handle the case where a channel might be closed. This prevents panic
and ensures graceful shutdowns.
1. For small structs, use value receivers to avoid unnecessary heap allocations.
Use pointer receivers for large structs or when mutating the receiver.
1. Only use goroutines when necessary. Excessive goroutines can lead to high
memory consumption and increased complexity.
1. Use `sync.Cond` for more complex synchronization needs that cannot be met
with simple mutexes and channels.
1. Reflection is powerful but should be used sparingly as it can lead to code
that is hard to understand and maintain. Prefer type-safe solutions.
1. Avoid storing large or complex data in context. Context should be used for
request-scoped values like deadlines, cancellation signals, and
authentication tokens.
1. Use `runtime.Callers` and `runtime.CallersFrames` to capture stack traces for
debugging and logging purposes.
1. Use the `testing.TB` interface to write helper functions that can be used
with both `*testing.T` and `*testing.B`.
1. Use struct embedding to reuse code across multiple structs. This is a form of
composition that can simplify code reuse.
1. Prefer defining explicit interfaces in your packages rather than relying on
implicit interfaces. This makes the intended use of interfaces clearer and
the code more maintainable.
# Author
[@sneak](https://sneak.berlin)
&lt;[sneak@sneak.berlin](mailto:sneak@sneak.berlin)&gt;
# License
MIT. See [LICENSE](../LICENSE).

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# JavaScript / ECMAScript / ES6
1. Use `const` for everything. If you need to reassign, use `let`. Never use
`var`.
1. Use yarn for package management, avoid using npm.
1. Use LTS node versions.
1. Use `prettier` for code formatting, with four spaces for indentation.
1. At a minimum, `npm run test` and `npm run build` should work (complete the
appropriate scripts in `package.json`). The `Makefile` should call these, do
not duplicate the scripts in the `Makefile`.
# Author
[@sneak](https://sneak.berlin)
&lt;[sneak@sneak.berlin](mailto:sneak@sneak.berlin)&gt;
# License
MIT. See [LICENSE](../LICENSE).

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# Python
1. Format all code with `black`, with four space indents.
2. Put all code in functions. If you are writing a script, put the script in a
function called `main` and call `main()` at the end of the script using the
standard invocation:
```python
if __name__ == "__main__":
main()
```
# Author
[@sneak](https://sneak.berlin)
&lt;[sneak@sneak.berlin](mailto:sneak@sneak.berlin)&gt;
# License
MIT. See [LICENSE](../LICENSE).