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Contributing happens via "Pull requests" (PR) on github. Every PR needs to be reviewed before it can be merged and the Continuous Integration should be green.
The PR has to be approved by two core developers or by Araq.
There are 4 types of tests:
runnableExamplesdocumentation comment tests, ran bynim doc mymod.nimThese end up in documentation and ensure documentation stays in sync with code.- separate test files, e.g.:
tests/stdlib/tos.nim. In nim repo, testament (see below) runs all $nim/tests/*/t*.nim test files; for nimble packages, see https://github.com/nim-lang/nimble#tests. - (deprecated) tests in
when isMainModule:block, ran bynim r mymod.nim.nimble testcan run those in nimble packages when specified in a task "test". - (not preferred) .. code-block:: nim RST snippets; these should only be used in rst sources, in nim sources runnableExamples should now always be preferred to those for several reasons (cleaner syntax, syntax highlights, batched testing, and rdoccmd allows customization).
Not all the tests follow the convention here, feel free to change the ones that don't. Always leave the code cleaner than you found it.
Each stdlib module (anything under lib/, e.g. lib/pure/os.nim) should
preferably have a corresponding separate test file, e.g. tests/stdlib/tos.nim.
The old convention was to add a when isMainModule: block in the source file,
which only gets executed when the tester is building the file.
Each test should be in a separate block: statement, such that
each has its own scope. Use boolean conditions and doAssert for the
testing by itself, don't rely on echo statements or similar; in particular, avoid
things like echo "done". Don't use unittest.suite and unittest.test.
Sample test:
block: # bug #1234
static: doAssert 1+1 == 2
block: # bug #1235
var seq2D = newSeqWith(4, newSeq[bool](2))
seq2D[0][0] = true
seq2D[1][0] = true
seq2D[0][1] = true
doAssert seq2D == @[@[true, true], @[true, false],
@[false, false], @[false, false]]
# doAssert with `not` can now be done as follows:
doAssert not (1 == 2)Always refer to a GitHub issue using the following exact syntax: bug #1234 as shown above, so that it's consistent and easier to search or for tooling. Some browser extensions (e.g. https://github.com/sindresorhus/refined-github) will even turn those in clickable links when it works.
Rationale for using a separate test file instead of when isMainModule: block: * allows custom compiler flags or testing options (see details below) * faster CI since they can be joined in megatest (combined into a single test) * avoids making the parser do un-necessary work when a source file is merely imported * avoids mixing source and test code when reporting line of code statistics or code coverage
The tests for the compiler use a testing tool called testament. They are all
located in tests/ (e.g.: tests/destructor/tdestructor3.nim).
Each test has its own file. All test files are prefixed with t. If you want
to create a file for import into another test only, use the prefix m.
At the beginning of every test is the expected behavior of the test. Possible keys are:
cmd: A compilation command template e.g.nim $target --threads:on $options $fileoutput: The expected output (stdout + stderr), most likely viaechoexitcode: Exit code of the test (viaexit(number))errormsg: The expected compiler error messagefile: The file the errormsg was produced atline: The line the errormsg was produced at
For a full spec, see here: testament/specs.nim
An example of a test:
discard """
errormsg: "type mismatch: got (PTest)"
"""
type
PTest = ref object
proc test(x: PTest, y: int) = nil
var buf: PTest
buf.test()You can run the tests with
./koch tests
which will run a good subset of tests. Some tests may fail. If you only want to see the output of failing tests, go for
./koch tests --failing all
You can also run only a single category of tests. A category is a subdirectory
in the tests directory. There are a couple of special categories; for a
list of these, see testament/categories.nim, at the bottom.
./koch tests c lib # compiles/runs stdlib modules, including `isMainModule` tests ./koch tests c megatest # runs a set of tests that can be combined into 1
To run a single test:
./koch test run <category>/<name> # e.g.: tuples/ttuples_issues ./koch test run tests/stdlib/tos.nim # can also provide relative path
For reproducible tests (to reproduce an environment more similar to the one
run by Continuous Integration on travis/appveyor), you may want to disable your
local configuration (e.g. in ~/.config/nim/nim.cfg) which may affect some
tests; this can also be achieved by using
export XDG_CONFIG_HOME=pathtoAlternateConfig before running ./koch
commands.
Test failures can be grepped using Failure:.
The tester can compare two test runs. First, you need to create a reference test. You'll also need to the commit id, because that's what the tester needs to know in order to compare the two.
git checkout devel DEVEL_COMMIT=$(git rev-parse HEAD) ./koch tests
Then switch over to your changes and run the tester again.
git checkout your-changes ./koch tests
Then you can ask the tester to create a testresults.html which will
tell you if any new tests passed/failed.
./koch tests --print html $DEVEL_COMMIT
Backward compatibility is important, so instead of a rename you need to deprecate the old name and introduce a new name:
# for routines (proc/template/macro/iterator) and types:
proc oldProc(a: int, b: float): bool {.deprecated:
"deprecated since v1.2.3; use `newImpl: string -> int` instead".} = discard
# for (const/var/let/fields) the msg is not yet supported:
const Foo {.deprecated.} = 1
# for enum types, you can deprecate the type or some elements
# (likewise with object types and their fields):
type Bar {.deprecated.} = enum bar0, bar1
type Barz = enum baz0, baz1 {.deprecated.}, baz2See also Deprecated pragma in the manual.
When contributing new procs, be sure to add documentation, especially if
the proc is public. Even private procs benefit from documentation and can be
viewed using nim doc --docInternal foo.nim.
Documentation begins on the line
following the proc definition, and is prefixed by ## on each line.
Runnable code examples are also encouraged, to show typical behavior with a few
test cases (typically 1 to 3 assert statements, depending on complexity).
These runnableExamples are automatically run by nim doc mymodule.nim
as well as testament and guarantee they stay in sync.
See parentDir example.
The RestructuredText Nim uses has a special syntax for including code snippets
embedded in documentation; these are not run by nim doc and therefore are
not guaranteed to stay in sync, so runnableExamples is usually preferred:
proc someproc*(): string =
## Returns "something"
##
## .. code-block::
## echo someproc() # "something"
result = "something" # single-hash comments do not produce documentationThe .. code-block:: nim followed by a newline and an indentation instructs the
nim doc command to produce syntax-highlighted example code with the
documentation (.. code-block:: is sufficient from inside a nim module).
When forward declaration is used, the documentation should be included with the first appearance of the proc.
proc hello*(): string
## Put documentation here
proc nothing() = discard
proc hello*(): string =
## ignore this
echo "hello"The preferred documentation style is to begin with a capital letter and use the third-person singular. That is, between:
proc hello*(): string =
## Returns "hello"
result = "hello"or
proc hello*(): string =
## say hello
result = "hello"the first is preferred.
Note: these are general guidelines, not hard rules; there are always exceptions. Code reviews can just point to a specific section here to save time and propagate best practices.
New defined(foo) symbols need to be prefixed by the nimble package name, or by nim for symbols in nim sources (e.g. compiler, standard library). This is to avoid name conflicts across packages.
# if in nim sources
when defined(allocStats): discard # bad, can cause conflicts
when defined(nimAllocStats): discard # preferred
# if in a pacakge `cligen`:
when defined(debug): discard # bad, can cause conflicts
when defined(cligenDebug): discard # preferredTake advantage of no implicit bool conversion
doAssert isValid() == true
doAssert isValid() # preferredDesign with method call syntax chaining in mind
proc foo(cond: bool, lines: seq[string]) # bad
proc foo(lines: seq[string], cond: bool) # preferred
# can be called as: `getLines().foo(false)`Use exceptions (including assert / doAssert) instead of quit
rationale: https://forum.nim-lang.org/t/4089
quit() # bad in almost all cases
doAssert() # preferredUse doAssert (or require, etc), not assert in all tests so they'll
be enabled even in release mode (except for tests in runnableExamples blocks
which for which nim doc ignores -d:release).
when isMainModule:
assert foo() # bad
doAssert foo() # preferredDelegate printing to caller: return string instead of calling echo
rationale: it's more flexible (e.g. allows the caller to call custom printing,
including prepending location info, writing to log files, etc).
proc foo() = echo "bar" # bad
proc foo(): string = "bar" # preferred (usually)[Ongoing debate] Consider using Option instead of return bool + var argument, unless stack allocation is needed (e.g. for efficiency).
proc foo(a: var Bar): bool
proc foo(): Option[Bar]Tests (including in testament) should always prefer assertions over echo,
except when that's not possible. It's more precise, easier for readers and
maintainers to where expected values refer to. See for example
nim-lang#9335 and https://forum.nim-lang.org/t/4089
echo foo() # adds a line for testament in `output:` block inside `discard`.
doAssert foo() == [1, 2] # preferred, except when not possible to do so.Important, critical bugfixes that have a tiny chance of breaking somebody's code should be backported to the latest stable release branch (currently 1.4.x) and maybe also all the way back to the 1.0.x branch. The commit message should contain the tag
[backport]for "backport to all stable releases" and the tag[backport:$VERSION]for backporting to the given $VERSION.If you introduce changes which affect backward compatibility, make breaking changes, or have PR which is tagged as
[feature], the changes should be mentioned in the changelog.All changes introduced by the commit (diff lines) must be related to the subject of the commit.
If you change something unrelated to the subject parts of the file, because your editor reformatted automatically the code or whatever different reason, this should be excluded from the commit.
Tip: Never commit everything as is using
git commit -a, but review carefully your changes withgit add -p.Changes should not introduce any trailing whitespace.
Always check your changes for whitespace errors using
git diff --checkor add the followingpre-commithook:#!/bin/sh git diff --check --cached || exit $?
Describe your commit and use your common sense. Example commit message:
Fixes #123; refs #124indicates that issue
#123is completely fixed (GitHub may automatically close it when the PR is committed), wheres issue#124is referenced (e.g.: partially fixed) and won't close the issue when committed.PR body (not just PR title) should contain references to fixed/referenced github issues, e.g.: fix #123 or refs #123. This is so that you get proper cross referencing from linked issue to the PR (github won't make those links with just PR title, and commit messages aren't always sufficient to ensure that, e.g. can't be changed after a PR is merged).
Commits should be always be rebased against devel (so a fast forward merge can happen)
e.g.: use
git pull --rebase origin devel. This is to avoid messing up git history. Exceptions should be very rare: when rebase gives too many conflicts, simply squash all commits using the script shown in nim-lang#9356Do not mix pure formatting changes (e.g. whitespace changes, nimpretty) or automated changes (e.g. nimfix) with other code changes: these should be in separate commits (and the merge on GitHub should not squash these into 1).
- Continuous Integration is by default run on every push in a PR; this clogs
the CI pipeline and affects other PR's; if you don't need it (e.g. for WIP or
documentation only changes), add
[ci skip]to your commit message title. This convention is supported by Appveyor and Travis. - Consider enabling CI (azure, GitHub actions and builds.sr.ht) in your own Nim fork, and waiting for CI to be green in that fork (fixing bugs as needed) before opening your PR in the original Nim repo, so as to reduce CI congestion. Same applies for updates on a PR: you can test commits on a separate private branch before updating the main PR.
- First check the CI logs and search for FAIL to find why CI failed; if the failure seems related to your PR, try to fix the code instead of restarting CI.
- If CI failure seems unrelated to your PR, it could be caused by a flaky test. File a bug for it if it isn't already reported. A PR push (or opening/closing PR) will re-trigger all CI jobs (even successful ones, which can be wasteful). Instead, follow these instructions to only restart the jobs that failed:
- Azure: if on your own fork, it's possible from inside azure console (e.g. dev.azure.com/username/username/_build/results?buildId=1430&view=results) via rerun failed jobs on top. If either on you own fork or in Nim repo, it's possible from inside GitHub UI under checks tab, see timotheecour#211 (comment)
- GitHub actions: under "Checks" tab, click "Re-run jobs" in the right.
- builds.sr.ht: create a sourcehut account so you can restart a PR job as illustrated
Whenever possible, use GitHub's new 'Suggested change' in code reviews, which saves time explaining the change or applying it; see also https://forum.nim-lang.org/t/4317
When reviewing large diffs that may involve code moving around, GitHub's interface doesn't help much as it doesn't highlight moves. Instead, you can use something like this, see visual results here:
git fetch origin pull/10431/head && git checkout FETCH_HEAD git diff --color-moved-ws=allow-indentation-change --color-moved=blocks HEAD^In addition, you can view GitHub-like diffs locally to identify what was changed within a code block using diff-highlight or diff-so-fancy, e.g.:
# put this in ~/.gitconfig: [core] pager = "diff-so-fancy | less -R" # or: use: `diff-highlight`
As outlined in nim-lang/RFCs#173 there are a couple of guidelines about what should go into the stdlib, what should be added and what eventually should be removed.
Maybe in the future the compiler itself can depend on Nimble packages but for the time being, we strive to have zero dependencies in the compiler as the compiler is the root of the bootstrapping process and is also used to build Nimble.
These are types most packages need to agree on for better interoperability,
for example Option[T]. This rule also covers the existing collections like
Table, CountTable etc. "Sorted" containers based on a tree-like data
structure are still missing and should be added.
Time handling, especially the Time type are also covered by this rule.
Reason: There is no benefit in moving them around just to fullfill some design fashion as in "Nim's core MUST BE SMALL". If you don't like an existing module, don't import it. If a compilation target (e.g. JS) cannot support a module, document this limitation.
This covers modules like os, osproc, strscans, strutils,
strformat, etc.
Reason: Generally speaking as external dependencies they are not exposed to enough users so that we can see if the shortcuts provide enough benefit or not. Many programmers avoid external dependencies, even moreso for "tiny syntactic improvements". However, this is only true for really good syntactic improvements that have the potential to clean up other parts of the Nim library substantially. If in doubt, new stdlib modules should start as external, successful Nimble packages.
As we strive for higher quality everywhere, it's easier to adopt existing, battle-tested modules eventually rather than creating modules from scratch.
As long as they are documented and tested well, adding little helpers to existing modules is acceptable. For two reasons:
- It makes Nim easier to learn and use in the long run.
("Why does sequtils lack a
countIt? Because version 1.0 happens to have lacked it? Silly...") - To encourage contributions. Contributors often start with PRs that add simple things and then they stay and also fix bugs. Nim is an open source project and lives from people's contributions and involvement. Newly introduced issues have to be balanced against motivating new people. We know where to find perfectly designed pieces of software that have no bugs -- these are the systems that nobody uses.
1. New stdlib modules should go under Nim/lib/std/. The rationale is to require users to import via import std/foo instead of import foo, which would cause potential conflicts with nimble packages. Note that this still applies for new modules in existing logical directories, e.g.: use lib/std/collections/foo.nim, not lib/pure/collections/foo.nim.
2. New module names should prefer plural form whenever possible, e.g.: std/sums.nim instead of std/sum.nim. In particular, this reduces chances of conflicts between module name and the symbols it defines. Furthermore, module names should use snake_case and not use capital letters, which cause issues when going from an OS without case sensitivity to an OS with it.