Rules

Ur has 37 lint rules. ur check and ur lint run the rules that are on by default, and an optional rule once a project turns it on or names it with --rule. ur report runs the opportunities. Each rule's page shows an example and what Ur prints for it.

Code

Code that does nothing, says the same thing twice, or misuses what it touches.

`duplicated-data`	The same literal values are written out in more than one place	On by default
`mutated-while-iterating`	A loop resizes the collection it walks	On by default
`negated-operator`	`not` written before a membership or identity test	On by default
`no-comments`	An ordinary comment outside the file's header	Optional
`semantic-clone`	Code with the same behavior appears in more than one place	On by default
`stray-env-var`	Environment variables are used outside an env file	On by default
`trivial-expression`	An expression always gives the same answer, or hands back one of its inputs	On by default

Tests

Tests that cannot fail, or whose failure would not say where to look, from Google's Testing Blog and its Effective Testing.

`circular-expectation`	A test computes the value it expects	On by default
`logic-in-test`	Logic in a test hides what it checks	On by default
`missing-assertion`	A test checks nothing	On by default
`opaque-test`	A test asserts but writes no value of its own	On by default
`overloaded-test`	A test checks one scenario, then sets up and checks an unrelated one	On by default
`repeated-argument`	A call is given the same value for two parameters	On by default
`tautological-assertion`	An assertion compares a value with itself	On by default
`trivial-inputs`	A test passes the code it tests only default values	On by default
`uninformative-assertion`	An assertion is given only the result of a comparison	On by default
`vacuous-assertion`	An assertion that cannot fail	On by default

Lean proofs

Theorems that rest on proofs Lean has not checked.

`hand-written-dual`	A Lean theorem that states another's order dual, written by hand	Optional
`rests-on-unproved`	A Lean theorem whose proof reads a declaration that is not proved	On by default
`unchecked-proof`	A Lean proof that Lean takes on trust rather than checks	On by default

Urscal grammars

Grammar rules that never match, or conditions that change nothing.

`grammar-dead-condition`	A condition tag that holds for no release, dialect, or feature	On by default
`grammar-redundant-condition`	A condition tag that holds wherever its construct can occur	On by default
`grammar-shadowed-alternative`	An alternative of an ordered choice that an earlier alternative always wins	On by default
`grammar-unreachable-sort`	A sort that no start rule reaches	On by default

Text

Optional rules over a file's text, for projects that want them: off until a project's ur.toml or --rule turns one on.

`ad-hoc-motion`	A transition or animation written ad hoc	Optional
`deep-nesting`	A line indented deeper than its project allows	Optional
`hardcoded-color`	A color written out instead of a theme token	Optional
`hardcoded-font`	A font stack written out instead of a theme token	Optional
`inline-svg`	An SVG drawn inline in component source	Optional
`long-file`	A file longer than its project allows	Optional
`stray-emoji`	An emoji in a file	Optional
`stray-todo`	A marker of work left for later	Optional

Opportunities

Code of one shape written out by hand in many places, which ur report ranks by the lines sharing it would save. They never fail a check.

`boilerplate-recursion`	A recursive walk over a type is written out by hand, arm by arm	Runs under ur report
`constructor-boilerplate`	One tree of constructors is built by hand at many sites	Runs under ur report
`duplicated-name-list`	One set of names is written out by hand in several places	Runs under ur report
`near-miss-clone`	Blocks of code are alike but for a few names or literals	Runs under ur report
`suppression-debt`	Many `ur-allow` comments excuse code of one shape	Runs under ur report