@fimbul/mimir

Mímir

Core rules, formatters and configurations of the Fimbullinter project.

Make sure to also read the full documentation of all available modules.

Purpose

This library contains all core rules, formatters and configuration presets of the Fimbullinter project. It's used internally by Wotan.

Rules

Rule	Description	Difference to TSLint rule / Why you should use it
await-async-result	Warns about not using the result of a call to an async function inside async functions. requires type information	TSLint's no-floating-promises requires you to specify a list of Promise names, it checks outside of async functions and only requires you to register the onrejected callback.
await-only-promise	Finds uses of await on non-Promise values. Also checks for await loops. requires type information	Works for all PromiseLike and Thenable types out of the box without any configuration.
generator-require-yield	Require at least one yield inside generator functions.	There's no similar TSLint rule.
no-debugger	Ban debugger; statements from your production code.	Performance!
no-fallthrough	Prevents unintentional fallthough in switch statements from one case to another. If the fallthrough is intended, add a comment that matches /^\s*falls? ?through\b/i.	Allows more comment variants such as fallthrough or fall through.
no-inferred-empty-object	Warns if a type parameter is inferred as {} because the compiler cannot find any inference site.	Really checks every type parameter of function, method and constructor calls. Correctly handles type parameters from JSDoc comments. Recognises type parameter defaults on all merged declarations.
no-return-await	Warns for unnecesary return await foo; when you can simply return foo;	The same as TSLint's rule. I wrote both, but this one is faster.
no-unreachable-code	Warns about statements that will never be executed. Works like TypeScript's dead code detection but doesn't fail compilation because it's a lint error.	TSLint removed their no-unreachable rule in v4.0.0.
no-unsafe-finally	Forbids control flow statements return, throw, break and continue inside the finally block of a try statement.	Performance!
no-unstable-api-use	Finds uses of deprecated and experimental variables, classes, properties, functions, signatures, ... requires type information	This rule checks element accesses (foo[bar]), JSX elements, chained function calls (getFn()()) in addition to what TSLint's deprecation rule does and has more useful error reporting.
no-unused-expression	Warns about side-effect free expressions whose value is not used	This one is a bit stricter than TSLint's no-unused-expression and checks for loops in addition.
no-unused-label	Warns about labels that are never used or at the wrong position.	TSLint only has label-position which doesn't check for unused labels.
no-nan-compare	Don't compare with NaN, use isNaN(number) or Number.isNaN(number) instead.	Performance!
no-useless-assertion	Detects type assertions that don't change the type or are not necessary in the first place. requires type information	TSLint's no-unnecessary-type-assertion does not detect assertions needed to silence the compiler warning Variable ... is used before being assigned. The Wotan builtin rule also checks whether the assertion is necessary at all or the receiver accepts the original type.
no-useless-initializer	Detects unnecessary initialization with undefined.	TSLint's rule no-unnecessary-initializer doesn't fix all parameter initializers and gives false positives for destructuring.
prefer-dot-notation	Prefer obj.foo over obj['foo'] where possible.	Same as TSLint's no-string-literal rule, but more performant.
prefer-number-isnan	Prefer ES2015's Number.isNaN over the global isNaN mainly for performance. requires type information	No similar rule in TSLint.
prefer-object-spread	Prefer object spread over Object.assign for copying properties to a new object. requires type information	Performance, and better handling of parens in fixer and avoids false positives that would cause a compile error when fixed.
syntaxcheck	Reports syntax errors as lint errors. This rule is not enabled in wotan:recommended. requires type information	Used to be part of the deprecated tslint --type-check
trailing-newline	Requires a line break at the end of each file.	Nothing fancy here :(
try-catch-return-await	Companion of no-return-await because inside a try-catch block you should await returned promises to correctly enter the catch on rejection and/or the finally block after completion.	TSLint has no similar rule.
typecheck	TypeScript's compiler errors as lint errors. This rule is not enabled in wotan:recommended. requires type information	Like the deprecated tslint --type-check but formatted and can be disabled like any other rule.

Formatters

• stylish
• json

Configuration Presets

• wotan:recommended contains recommended builtin rules. This configuration only adds new rules in major versions.
• wotan:latest contains recommended builtin rules and is updated in minor versions. Be aware that this might cause your build to break.

License

Apache-2.0 © Klaus Meinhardt

Changelog

v0.4.0

This release contains a lot of refactoring and structural changes:

• renamed await-promise to await-only-promise
• renamed deprecation to no-unstable-api-use

Two new packages were split from the wotan package:

• ymir contains all base types and classes. This package can be used by extension and rule authors to not depend on the full wotan runtime.
• mimir contains all rules, formatters and configuration presets. Together with ymir this package allows rules to be executed in a different runtime without depending on the whole wotan package

Features:

• Added recipes to Readme
• new rule await-async-result
• new rule generator-require-yield
• new rule no-nan-compare
• new rule no-unreachable-code
• new rule prefer-dot-notation
• new rule prefer-number-isnan
• new rule prefer-object-spread
• no-unstable-api-use (previously deprecation) also checks @experimental tag

Bugfixes:

no-unused-label no longer forbids labels on statements other than loops and switch