excelize/CONTRIBUTING.md

# Contributing to excelize

Want to hack on excelize? Awesome! This page contains information about reporting issues as well as some tips and
guidelines useful to experienced open source contributors. Finally, make sure
you read our [community guidelines](#community-guidelines) before you
start participating.

## Topics

* [Reporting Security Issues](#reporting-security-issues)
* [Design and Cleanup Proposals](#design-and-cleanup-proposals)
* [Reporting Issues](#reporting-other-issues)
* [Quick Contribution Tips and Guidelines](#quick-contribution-tips-and-guidelines)
* [Community Guidelines](#community-guidelines)

## Reporting security issues

The excelize maintainers take security seriously. If you discover a security
issue, please bring it to their attention right away!

Please **DO NOT** file a public issue, instead send your report privately to
[xuri.me](https://xuri.me).

Security reports are greatly appreciated and we will publicly thank you for it.
We currently do not offer a paid security bounty program, but are not
ruling it out in the future.

## Reporting other issues

A great way to contribute to the project is to send a detailed report when you
encounter an issue. We always appreciate a well-written, thorough bug report,
and will thank you for it!

Check that [our issue database](https://github.com/xuri/excelize/issues)
doesn't already include that problem or suggestion before submitting an issue.
If you find a match, you can use the "subscribe" button to get notified on
updates. Do *not* leave random "+1" or "I have this too" comments, as they
only clutter the discussion, and don't help resolving it. However, if you
have ways to reproduce the issue or have additional information that may help
resolving the issue, please leave a comment.

When reporting issues, always include the output of `go env`.

Also include the steps required to reproduce the problem if possible and
applicable. This information will help us review and fix your issue faster.
When sending lengthy log-files, consider posting them as a gist [https://gist.github.com](https://gist.github.com).
Don't forget to remove sensitive data from your logfiles before posting (you can
replace those parts with "REDACTED").

## Quick contribution tips and guidelines

This section gives the experienced contributor some tips and guidelines.

### Pull requests are always welcome

Not sure if that typo is worth a pull request? Found a bug and know how to fix
it? Do it! We will appreciate it. Any significant improvement should be
documented as [a GitHub issue](https://github.com/xuri/excelize/issues) before
anybody starts working on it.

We are always thrilled to receive pull requests. We do our best to process them
quickly. If your pull request is not accepted on the first try,
don't get discouraged!

### Design and cleanup proposals

You can propose new designs for existing excelize features. You can also design
entirely new features. We really appreciate contributors who want to refactor or
otherwise cleanup our project.

We try hard to keep excelize lean and focused. Excelize can't do everything for
everybody. This means that we might decide against incorporating a new feature.
However, there might be a way to implement that feature *on top of* excelize.

### Conventions

Fork the repository and make changes on your fork in a feature branch:

* If it's a bug fix branch, name it XXXX-something where XXXX is the number of
    the issue.
* If it's a feature branch, create an enhancement issue to announce
    your intentions, and name it XXXX-something where XXXX is the number of the
    issue.

Submit unit tests for your changes. Go has a great test framework built in; use
it! Take a look at existing tests for inspiration. Run the full test on your branch before
submitting a pull request.

Update the documentation when creating or modifying features. Test your
documentation changes for clarity, concision, and correctness, as well as a
clean documentation build.

Write clean code. Universally formatted code promotes ease of writing, reading,
and maintenance. Always run `gofmt -s -w file.go` on each changed file before
committing your changes. Most editors have plug-ins that do this automatically.

Pull request descriptions should be as clear as possible and include a reference
to all the issues that they address.

### Successful Changes

Before contributing large or high impact changes, make the effort to coordinate
with the maintainers of the project before submitting a pull request. This
prevents you from doing extra work that may or may not be merged.

Large PRs that are just submitted without any prior communication are unlikely
to be successful.

While pull requests are the methodology for submitting changes to code, changes
are much more likely to be accepted if they are accompanied by additional
engineering work. While we don't define this explicitly, most of these goals
are accomplished through communication of the design goals and subsequent
solutions. Often times, it helps to first state the problem before presenting
solutions.

Typically, the best methods of accomplishing this are to submit an issue,
stating the problem. This issue can include a problem statement and a
checklist with requirements. If solutions are proposed, alternatives should be
listed and eliminated. Even if the criteria for elimination of a solution is
frivolous, say so.

Larger changes typically work best with design documents. These are focused on
providing context to the design at the time the feature was conceived and can
inform future documentation contributions.

### Commit Messages

Commit messages must start with a capitalized and short summary
written in the imperative, followed by an optional, more detailed explanatory
text which is separated from the summary by an empty line.

Commit messages should follow best practices, including explaining the context
of the problem and how it was solved, including in caveats or follow up changes
required. They should tell the story of the change and provide readers
understanding of what led to it.

In practice, the best approach to maintaining a nice commit message is to
leverage a `git add -p` and `git commit --amend` to formulate a solid
changeset. This allows one to piece together a change, as information becomes
available.

If you squash a series of commits, don't just submit that. Re-write the commit
message, as if the series of commits was a single stroke of brilliance.

That said, there is no requirement to have a single commit for a PR, as long as
each commit tells the story. For example, if there is a feature that requires a
package, it might make sense to have the package in a separate commit then have
a subsequent commit that uses it.

Remember, you're telling part of the story with the commit message. Don't make
your chapter weird.

### Review

Code review comments may be added to your pull request. Discuss, then make the
suggested modifications and push additional commits to your feature branch. Post
a comment after pushing. New commits show up in the pull request automatically,
but the reviewers are notified only when you comment.

Pull requests must be cleanly rebased on top of master without multiple branches
mixed into the PR.

**Git tip**: If your PR no longer merges cleanly, use `rebase master` in your
feature branch to update your pull request rather than `merge master`.

Before you make a pull request, squash your commits into logical units of work
using `git rebase -i` and `git push -f`. A logical unit of work is a consistent
set of patches that should be reviewed together: for example, upgrading the
version of a vendored dependency and taking advantage of its now available new
feature constitute two separate units of work. Implementing a new function and
calling it in another file constitute a single logical unit of work. The very
high majority of submissions should have a single commit, so if in doubt: squash
down to one.

After every commit, make sure the test passes. Include documentation
changes in the same pull request so that a revert would remove all traces of
the feature or fix.

Include an issue reference like `Closes #XXXX` or `Fixes #XXXX` in commits that
close an issue. Including references automatically closes the issue on a merge.

Please see the [Coding Style](#coding-style) for further guidelines.

### Merge approval

The excelize maintainers use LGTM (Looks Good To Me) in comments on the code review to
indicate acceptance.

### Sign your work

The sign-off is a simple line at the end of the explanation for the patch. Your
signature certifies that you wrote the patch or otherwise have the right to pass
it on as an open-source patch. The rules are pretty simple: if you can certify
the below (from [developercertificate.org](http://developercertificate.org/)):

```text
Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
Suite D4700
San Francisco, CA, 94129

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.
```

Then you just add a line to every git commit message:

```text
Signed-off-by: Ri Xu https://xuri.me
```

Use your real name (sorry, no pseudonyms or anonymous contributions.)

If you set your `user.name` and `user.email` git configs, you can sign your
commit automatically with `git commit -s`.

### How can I become a maintainer

First, all maintainers have 3 things

* They share responsibility in the project's success.
* They have made a long-term, recurring time investment to improve the project.
* They spend that time doing whatever needs to be done, not necessarily what
 is the most interesting or fun.

Maintainers are often under-appreciated, because their work is harder to appreciate.
It's easy to appreciate a really cool and technically advanced feature. It's harder
to appreciate the absence of bugs, the slow but steady improvement in stability,
or the reliability of a release process. But those things distinguish a good
project from a great one.

Don't forget: being a maintainer is a time investment. Make sure you
will have time to make yourself available. You don't have to be a
maintainer to make a difference on the project!

If you want to become a meintainer, contact [xuri.me](https://xuri.me) and given a introduction of you.

## Community guidelines

We want to keep the community awesome, growing and collaborative. We need
your help to keep it that way. To help with this we've come up with some general
guidelines for the community as a whole:

* Be nice: Be courteous, respectful and polite to fellow community members:
  no regional, racial, gender, or other abuse will be tolerated. We like
  nice people way better than mean ones!

* Encourage diversity and participation: Make everyone in our community feel
  welcome, regardless of their background and the extent of their
  contributions, and do everything possible to encourage participation in
  our community.

* Keep it legal: Basically, don't get us in trouble. Share only content that
  you own, do not share private or sensitive information, and don't break
  the law.

* Stay on topic: Make sure that you are posting to the correct channel and
  avoid off-topic discussions. Remember when you update an issue or respond
  to an email you are potentially sending to a large number of people. Please
  consider this before you update. Also remember that nobody likes spam.

* Don't send email to the maintainers: There's no need to send email to the
  maintainers to ask them to investigate an issue or to take a look at a
  pull request. Instead of sending an email, GitHub mentions should be
  used to ping maintainers to review a pull request, a proposal or an
  issue.

### Guideline violations — 3 strikes method

The point of this section is not to find opportunities to punish people, but we
do need a fair way to deal with people who are making our community suck.

1. First occurrence: We'll give you a friendly, but public reminder that the
   behavior is inappropriate according to our guidelines.

2. Second occurrence: We will send you a private message with a warning that
   any additional violations will result in removal from the community.

3. Third occurrence: Depending on the violation, we may need to delete or ban
   your account.

**Notes:**

* Obvious spammers are banned on first occurrence. If we don't do this, we'll
  have spam all over the place.

* Violations are forgiven after 6 months of good behavior, and we won't hold a
  grudge.

* People who commit minor infractions will get some education, rather than
  hammering them in the 3 strikes process.

* The rules apply equally to everyone in the community, no matter how much
    you've contributed.

* Extreme violations of a threatening, abusive, destructive or illegal nature
    will be addressed immediately and are not subject to 3 strikes or forgiveness.

* Contact [xuri.me](https://xuri.me) to report abuse or appeal violations. In the case of
    appeals, we know that mistakes happen, and we'll work with you to come up with a
    fair solution if there has been a misunderstanding.

## Coding Style

Unless explicitly stated, we follow all coding guidelines from the Go
community. While some of these standards may seem arbitrary, they somehow seem
to result in a solid, consistent codebase.

It is possible that the code base does not currently comply with these
guidelines. We are not looking for a massive PR that fixes this, since that
goes against the spirit of the guidelines. All new contributions should make a
best effort to clean up and make the code base better than they left it.
Obviously, apply your best judgement. Remember, the goal here is to make the
code base easier for humans to navigate and understand. Always keep that in
mind when nudging others to comply.

The rules:

1. All code should be formatted with `gofmt -s`.
2. All code should pass the default levels of
   [`golint`](https://github.com/golang/lint).
3. All code should follow the guidelines covered in [Effective
   Go](http://golang.org/doc/effective_go.html) and [Go Code Review
   Comments](https://github.com/golang/go/wiki/CodeReviewComments).
4. Comment the code. Tell us the why, the history and the context.
5. Document _all_ declarations and methods, even private ones. Declare
   expectations, caveats and anything else that may be important. If a type
   gets exported, having the comments already there will ensure it's ready.
6. Variable name length should be proportional to its context and no longer.
   `noCommaALongVariableNameLikeThisIsNotMoreClearWhenASimpleCommentWouldDo`.
   In practice, short methods will have short variable names and globals will
   have longer names.
7. No underscores in package names. If you need a compound name, step back,
   and re-examine why you need a compound name. If you still think you need a
   compound name, lose the underscore.
8. No utils or helpers packages. If a function is not general enough to
   warrant its own package, it has not been written generally enough to be a
   part of a util package. Just leave it unexported and well-documented.
9. All tests should run with `go test` and outside tooling should not be
   required. No, we don't need another unit testing framework. Assertion
   packages are acceptable if they provide _real_ incremental value.
10. Even though we call these "rules" above, they are actually just
    guidelines. Since you've read all the rules, you now know that.

If you are having trouble getting into the mood of idiomatic Go, we recommend
reading through [Effective Go](https://golang.org/doc/effective_go.html). The
[Go Blog](https://blog.golang.org) is also a great resource. Drinking the
kool-aid is a lot easier than going thirsty.

## Code Review Comments and Effective Go Guidelines

[CodeLingo](https://codelingo.io) automatically checks every pull request against the following guidelines from [Effective Go](https://golang.org/doc/effective_go.html) and [Code Review Comments](https://github.com/golang/go/wiki/CodeReviewComments).

### Package Comment

Every package should have a package comment, a block comment preceding the package clause.
For multi-file packages, the package comment only needs to be present in one file, and any one will do.
The package comment should introduce the package and provide information relevant to the package as a
whole. It will appear first on the godoc page and should set up the detailed documentation that follows.

### Single Method Interface Name

By convention, one-method interfaces are named by the method name plus an -er suffix
or similar modification to construct an agent noun: Reader, Writer, Formatter, CloseNotifier etc.

There are a number of such names and it's productive to honor them and the function names they capture.
Read, Write, Close, Flush, String and so on have canonical signatures and meanings. To avoid confusion,
don't give your method one of those names unless it has the same signature and meaning. Conversely,
if your type implements a method with the same meaning as a method on a well-known type, give it the
same name and signature; call your string-converter method String not ToString.

### Avoid Annotations in Comments

Comments do not need extra formatting such as banners of stars. The generated output
may not even be presented in a fixed-width font, so don't depend on spacing for alignment—godoc,
like gofmt, takes care of that. The comments are uninterpreted plain text, so HTML and other
annotations such as _this_ will reproduce verbatim and should not be used. One adjustment godoc
does do is to display indented text in a fixed-width font, suitable for program snippets.
The package comment for the fmt package uses this to good effect.

### Comment First Word as Subject

Doc comments work best as complete sentences, which allow a wide variety of automated presentations.
The first sentence should be a one-sentence summary that starts with the name being declared.

### Good Package Name

It's helpful if everyone using the package can use the same name
to refer to its contents, which implies that the package name should
be good: short, concise, evocative. By convention, packages are
given lower case, single-word names; there should be no need for
underscores or mixedCaps. Err on the side of brevity, since everyone
using your package will be typing that name. And don't worry about
collisions a priori. The package name is only the default name for
imports; it need not be unique across all source code, and in the
rare case of a collision the importing package can choose a different
name to use locally. In any case, confusion is rare because the file
name in the import determines just which package is being used.

### Avoid Renaming Imports

Avoid renaming imports except to avoid a name collision; good package names
should not require renaming. In the event of collision, prefer to rename the
most local or project-specific import.

### Context as First Argument

Values of the context.Context type carry security credentials, tracing information,
deadlines, and cancellation signals across API and process boundaries. Go programs
pass Contexts explicitly along the entire function call chain from incoming RPCs
and HTTP requests to outgoing requests.

Most functions that use a Context should accept it as their first parameter.

### Do Not Discard Errors

Do not discard errors using _ variables. If a function returns an error,
check it to make sure the function succeeded. Handle the error, return it, or,
in truly exceptional situations, panic.

### Go Error Format

Error strings should not be capitalized (unless beginning with proper nouns
or acronyms) or end with punctuation, since they are usually printed following
other context. That is, use fmt.Errorf("something bad") not fmt.Errorf("Something bad"),
so that log.Printf("Reading %s: %v", filename, err) formats without a spurious
capital letter mid-message. This does not apply to logging, which is implicitly
line-oriented and not combined inside other messages.

### Use Crypto Rand

Do not use package math/rand to generate keys, even
throwaway ones. Unseeded, the generator is completely predictable.
Seeded with time.Nanoseconds(), there are just a few bits of entropy.
Instead, use crypto/rand's Reader, and if you need text, print to
hexadecimal or base64.