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Orion/ESLint
Orion 5.0 will replace our current JSLint validator with ESLint. This page captures ongoing issues.
Contents
Rule parity
Here's a table showing the equivalent validation rules in JSLint and ESLint. Rules that JSLint does not support are marked as Unsupported.
ESLint rule | JSLint option | JSLint message | Details |
---|---|---|---|
block-scoped-var | Always on | '{variable}' is already defined. |
|
brace-style | Unsupported | ||
camelcase | Unsupported | ||
complexity | Unsupported | ||
consistent-this | Unsupported | ||
curly | Always on |
|
|
dot-notation | sub | {a} is better written in dot notation. | |
eqeqeq | eqeqeq or eqeq |
|
|
guard-for-in | forin | The body of a for in should be wrapped in an if statement to filter unwanted properties from the prototype.
| |
max-depth | Unsupported | Enforces max depth of nested blocks within a function. | |
max-len | maxlen | Line too long. | Enforces a maximum line length. |
max-params | Unsupported | ||
max-statements | Unsupported | ||
new-cap | newcap | A constructor name should start with an uppercase letter. | |
new-parens | Always on | Missing '()' invoking a constructor. | Flags new Whatever
|
no-alert | devel | '{alert, confirm, prompt}' is not defined. | |
no-bitwise | bitwise | Unexpected use of '{operator}'. | JSLint disallows bitwise ops by default. |
no-caller | Unsupported | Flags references to arguments.callee and arguments.caller .
| |
no-catch-shadow | Always on | '{a}' is already defined. |
|
no-comma-dangle | Always on | Unexpected comma. | Flags trailing commas in object literals. |
no-cond-assign | Unsupported | Flags assignment in an if/while/do..while/for condition.
| |
no-console | devel | ||
no-control-regex | Unsupported | Flags control characters (U+0000–U+001F and U+007F) within the source argument to the RegExp constructor. | |
no-debugger | debug | All 'debugger' statements should be removed. | |
no-delete-var | Always on | Expected '.' and instead saw ';'. | Flags an attempt to delete a local variable.
|
no-div-regex | Always on | A regular expression literal can be confused with '/='. | Flags a regex literal starting with /=
|
no-dupe-keys | Always on | Duplicate key '{a}'. | Flags object literals that contain the same key more than once. |
no-else-return | Unsupported | Flags an else appearing after an if that contains a return .
| |
no-empty-class | Always on | Empty class. | Flags an empty character class [] within a regular expression.
|
no-empty-label | Always on | Label '{a}' on statement. | Flags a labeled statement that is not a switch , for , or while .
|
no-empty | Unsupported | Flags an empty block like if (something) { } .
| |
no-eq-null | Always on | Use '===' to compare with 'null'. | JSLint produces a similar warning when comparing against undefined .
|
no-eval | evil | eval is evil. | |
no-ex-assign | Always on | Do not assign to the exception parameter. | |
no-extra-semi | Always on | Unnecessary semicolon. | |
no-fallthrough | Unsupported | Flags a fallthrough case within a switch statement, unless it is explicitly commented.
| |
no-floating-decimal | Always on | A {leading, trailing} decimal point can be confused with a dot: '{n}'. | Flags numeric literals that have a leading or trailing decimal point. |
no-func-assign | Unsupported | Flags assignment to a variable that's already bound to a FunctionExpression .
| |
no-global-strict | Unsupported | Flags "use strict" applied to the entire Program.
| |
no-implied-eval | Always on | Implied eval is evil. Pass a function instead of a string. | Flags calls to the string-argument form of setTimeout and setInterval , which implicitly perform eval .
|
no-iterator | Always on | Reserved name '__iterator__'. | Flags use of __iterator__ as an identifier name or property key. |
no-label-var | Always on | '{label}' is already defined. | Flags labels that collide with an identifier. |
no-loop-func | Always on | Don't make functions within a loop. | |
no-mixed-requires | Flags Node.js require() s that mix different types of requires (core, module, file, computed).
| ||
no-multi-str | Flags use of ES5 multiline string literals. | ||
no-native-reassign | Always on |
|
Flags an attempt to reassign a native object like Math , Array, undefined , etc.
|
no-negated-in-lhs | Unsupported |
| |
no-new-array | Always on | Use the array literal notation []. | Flags new Array() .
|
no-new-func | Always on | The Function constructor is eval. | |
no-new-object | Always on | Use the object literal notation {}. | Flags new Object() .
|
no-new-wrappers | Do not use {String, Number, Boolean, Math, JSON} as a constructor. | Flags new applied to any of those.
| |
no-new | Always on | Do not use 'new' for side effects. | Flags uses of new operator in an expression that is not assigned to anything.
|
no-obj-calls | Partial support | Math is not a function.. |
|
no-octal-escape | Always on | Bad escapement. | Flags octal escapes in strings, for example var x = "Copyright \251";
|
no-octal | Always on | Don't use extra leading zeros '{n}'. | Flags number literals that begin with leading 0s, which indicate a (probably accidental) octal literal. |
no-plusplus | plusplus |
| |
no-proto | Always on |
|
Treated as a fatal parse error in JSLint. |
no-redeclare | Always on | '{a}' is already defined. | Usually results from having two for loops in the same function that share a loop variable declaration like var i=... .
|
no-return-assign | Unsupported |
| |
no-script-url | Always on | Script URL. |
|
no-self-compare | Unsupported | Flags comparisons where the left- and right-hand sides are the same. | |
no-shadow | Unsupported | Flags variables that have the same name as a variable declared in an outer scope. | |
no-spaced-func | |||
no-sync | stupid | Unexpected sync method: '{a}'. |
|
no-ternary | Unsupported | Flags any use of the ternary operator cond ? thenExpr : elseExpr
| |
no-undef-init | Always on | It is not necessary to initialize '{variable}' to 'undefined'. | |
no-undef | undef | '{variable}' is not defined. |
|
no-underscore-dangle | nomen | Dangling '_' | |
no-unreachable | Always on | Unreachable '{statement}' after '{control flow statement}'. | Flags statements that occur after a return , throw , etc.
|
no-unused-expressions | Always on | Expected an assignment or function call and instead saw an expression. | Flags expressions that appear in a statement context and don't cause side effects. |
no-unused-vars | Always on | Function declares unused variable '{a}'. (Orion) | Newer JSlint versions have an unparam option which works similarly. |
no-use-before-define | Always on | '{a}' was used before it was defined. | |
no-with | Always on | Expected an identifier and instead saw 'with'. | Treated as fatal parse error in JSLint. |
no-wrap-func | Always on | Do not wrap function literals in parens unless they are to be immediately invoked. | Flags a parenthesized function literal that is not immediately invoked, eg. (function fun(){})
|
one-var | onevar | Too many var statements. | Allows only 1 var statement per function.
|
quote-props | Unsupported | Requires object literal keys to be quoted with " or '. | |
quotes | Unsupported | Flags any use of single or double quote marks, depending on setting. | |
radix | Always on | Missing radix parameter. | Affects parseInt(). |
regex-spaces | Always on | Spaces are hard to count. Use {n}. | |
semi | Always on | Missing semicolon. | |
strict | strict | Flags any code that lacks the "use strict" pragma.
| |
unnecessary-strict | Unsupported | Flags "use strict" on a function when the entire Program is already in strict mode.
| |
use-isnan | Always on | Use the isNaN function to compare with NaN. | |
wrap-iife | immed |
|
Flags missing parens on immediately-invoked functions, eg. function(){ console.log('hi'); }();
|
wrap-regex | Always on | Wrap the /regexp/ literal in parens to disambiguate the slash operator. |
New rules
Ideas for new linting rules that we should write.
Name | Severity | Description |
---|---|---|
object-prototype-external | Warning | Flags calls to methods of Object.prototype that rely on the prototype chain. For example this code should be flagged:
Example (1) is unsafe, as As for this:
Example (2) technically relies on the prototype chain as well: the hasOwnProperty method is defined on Object.prototype, not Object. Object inherits the methods of Object.prototype through its prototype chain. However (2) is unlikely to fail, as sane JavaScript programs will not modify the global objects' prototypes. If we choose to flag (2), it should only be for style. |
|
Ignore | Flags missing documentation nodes on function declarations and function expressions when they appear as object properties |
missing-doc-items | Ignore | Flags missing documentation for parameters, returns, throws, etc on function declarations and function expressions when they appear as object properties |
unused-parameters | Error | Flags parameters in function declarations / expressions if they are not being used |
no-mixed-returns | Error | Flags functions that return more than one kind of item, for example returning String and Object |
Rule priority
Here are the rules we want to support, grouped by priority. Implemented rules are struck out.
Critical
- block-scoped-var
-
eqeqeq -
no-undef -
no-redeclare -
no-unused-vars -
no-use-before-define
Important
- guard-for-in
- no-dupe-keys
- no-octal
- no-with
- radix
-
semi - wrap-iife
Nice to have
- dot-notation
- new-cap
- new-parens
- no-caller
- no-comma-dangle
- no-implied-eval
- no-new-array
- no-new-object
- no-undef-init
- no-unused-expressions
- no-wrap-func
- use-isnan
Tests
- Every rule needs extensive unit tests
- Unit tests should use Mocha
Currently the tests are run from Node.js. They do not run in the browser (yet).
Test requirements
First install Node.js. Then open a console and install Mocha globally:
$ npm install mocha -g
Then from your Orion client repository, run these commands to install eslint's dependencies:
$ cd bundles/org.eclipse.orion.client.javascript/web/eslint/ $ npm install
Running the tests
From the bundles/org.eclipse.orion.client.javascript/web/eslint/
directory, simply run npm test
:
$ npm test > eslint@0.2.0-dev test c:\Users\mamacdon\code\orion\client\bundles\org.eclipse.orion.client.javascript\web\eslint > bash scripts/test.sh ...................................................................... ............... 85 passing (106ms)
To run only a subset of the tests, launch mocha from the command line, passing the test file:
$ mocha tests/lib/rules/semi.js ............ 12 passing (17ms)
You can also pass an entire directory:
$ mocha tests/lib/rules ...................................................................... .......... 80 passing (104ms)
To run only some tests from a file, use the --grep option:
$ mocha tests/lib/rules/semi.js --grep VariableDeclaration . 1 passing (5ms)
See Mocha usage options for more.
User interface
-
Should we have a UI for configuring what rules are active?Implemented. - Should we try to support
.eslintrc
? This would be an ideal project-scope setting. - Should we try to honor equivalent JSLint/JSHint flags when possible? For example
/*jslint eqeqeq:false */
could disable the eqeqeq rule on a per-file basis.- This would give compatibility with Orion codebase which uses these flags.
- OTOH, eslint now has its own syntax for this:
/*eslint ..*/
, which we should perhaps use instead.
i18n
We need to support i18n. Pre-req is bug 422278 (orion.edit.validator support for i18n).