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Orion/ESLint
Orion 5.0 moved to ESLint as the validator that ships with Orion. This page captures ongoing issues.
Contents
Rules
The following sections describe all of the rules currently available in Orion and ones that we plan to add in the future.
Potential Programming Problems
These rules report about problems with your code that might have undesired or incorrect results. Warnings from these rules should be addressed.
Rule | Default Severity | Available Since | Problem Message | Details |
---|---|---|---|---|
no-comma-dangle | Ignore | 8.0 | Trailing commas in object expressions are discouraged. | Flags trailing commas in object expressions. |
no-cond-assign | Error | 8.0 | Expected a conditional expression and instead saw an assignment. | Flags assignment in an if/while/do..while/for condition.
|
no-console | Error | 8.0 | Discouraged use of console in browser-based code. | Flags the use of console in browser-based code |
no-constant-condition | Error | 8.0 | Discouraged use of constant as a conditional expression. | Flags the use of a constant as a conditional expression |
no-debugger | Warning | 6.0 | debugger' statement use is discouraged. | Warns when the debugger keyword is used
|
no-dupe-keys | Error | 6.0 | Duplicate object key '{key}'. | Flags object literals that contain the same key more than once. |
no-empty-block | Warning | 7.0 | Empty block should be removed or commented. | Flags an empty block like if (something) { } .
|
no-extra-semi | Warning | 5.0 | Unnecessary semicolon. | Warns when a semi colon is found where it is not needed |
no-regex-spaces | Error | 8.0 | Avoid using multiple spaces in regular expressions. Use ' {${0}}' instead. | Flags regular expressions that have two or more subsequent spaces. |
no-reserved-keys | Error | 8.0 | Reserved words should not be used as property keys. | Checks to see if a JavaScript reserved word is being used as a property key |
no-sparse-arrays | Warning | 8.0 | Sparse array declarations should be avoided. | Flags sparse arrays with null elements like var arr = [1, ,2]
|
no-unreachable | Error | 6.0 | Unreachable code. | Flags statements that occur after a return , throw , etc.
|
use-isnan | Error | 6.0 | Use the isNaN function to compare with NaN. | Warns when a comparison is done against NaN without using the isNaN function
|
Best Practices
These rules are not necessarily problem with your code, but are warnings that you might be doing something you probably should not be.
Rule | Default Severity | Available Since | Problem Message | Details |
---|---|---|---|---|
block-scoped-var | Error | - | '{variable}' is already defined. |
|
curly | Ignore | 6.0 | Statements should be enclosed in braces. | |
eqeqeq | Warning | 5.0 |
|
|
missing-doc | Ignore | 5.0 | Missing documentation for function '{name}'. | Flags missing documentation nodes on function declarations and function expressions when they appear as object properties |
missing-doc-items | Ignore | - | Flags missing documentation for parameters, returns, throws, etc on function declarations and function expressions when they appear as object properties | |
no-caller | Error | 9.0 | arguments.{callee, caller} is deprecated. | Flags references to arguments.callee and arguments.caller .
|
no-eval | Ignore | 6.0 | 'eval' function calls are discouraged. | |
no-fallthrough | Error | 6.0 | Switch case may be entered by falling through previous case. If intended, add a new comment //$FALL-THROUGH$ on the line above | Flags a fallthrough case within a switch statement, unless it is explicitly commented.
|
no-implied-eval | Ignore | 6.0 | Implicit 'eval' function calls are discouraged. | Flags calls to the string-argument form of setTimeout and setInterval , which implicitly perform eval . This rule logic was merged to be part of the no-eval rule.
|
no-iterator | Error | 8.0 | Discouraged __iterator__ property use. | Flags use of __iterator__ as an identifier name or property key. |
no-new-array | Warning | 6.0 | Use the array literal notation []. | Flags new Array() .
|
no-new-func | Warning | 6.0 | The Function constructor is eval. | Flags new Function() .
|
no-new-object | Warning | 6.0 | Use the object literal notation {}. | Flags new Object() .
|
no-new-wrappers | Warning | 6.0 | Do not use {String, Number, Boolean, Math, JSON} as a constructor. | Flags new applied to any of those.
|
no-proto | Error | - |
|
Flags use of the property __proto__ as object keys or in assignments |
no-redeclare | Warning | 5.0 | '{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-self-compare | Error | - | Comparing a value to itself has no effect. | Flags comparisons where the left- and right-hand sides are the same. |
no-shadow | Warning | 8.0 | '{a}' is already declared in the upper scope. | Flags variables that have the same name as a variable declared in an upper scope. |
no-shadow-global | Warning | 9.0 | '{a}' shadows a global member. | Flags variables that have the same name as a variable declared in the global scope or specified environments. |
no-undef | Error | 5.0 | '{variable}' is not defined. |
|
no-unused-params | Warning | 6.0 | Parameter '{param}' is not used. | Flags parameters in function declarations / expressions if they are not being used |
no-unused-vars | Warning | 5.0 |
|
|
no-use-before-define | Warning | 5.0 | '{a}' was used before it was defined. | Warns when a variable or function is used before it is defined |
no-with | Warning | - | Expected an identifier and instead saw 'with'. | Treated as fatal parse error in JSLint. |
radix | Warning | 8.0 | Missing radix parameter. | Warns when parseInt() called without the 2nd parameter (radix). |
throw-error | Warning | 7.0 | Throw an Error instead. | Flags code that throws a non-Error, eg. throw "a problem occurred";
|
Code Style
These rules are not problems in any way but will warn based on certain accepted styles for coding.
Rule | Default Severity | Available Since | Problem Message | Details |
---|---|---|---|---|
missing-nls | Ignore | - | Flags String literals that are not properly NLS'd | |
new-parens | Error | 6.0 | Missing parentheses invoking constructor. | Flags new Whatever
|
no-mixed-returns | Error | - | Flags functions that return more than one kind of item, for example returning String and Object | |
no-undef-init | Warning | - | It is not necessary to initialize '{variable}' to 'undefined'. | |
semi | Warning | 5.0 | Missing semicolon. |
Implementing a new rule
This section explains how to implement a new linting rule. For brevity, all paths are given relative to bundles/org.eclipse.orion.client.javascript/web/ in the client repo.
First, create the tests and rule:
- Create a new test file for the rule at: /eslint/tests/lib/rules/{rule-name}.js.
- Link your test to the suite in /eslint/tests/load-tests.js.
- Implement the actual logic for your rule in /eslint/lib/load-rules-async.js.
At this point you should run the JS bundle tests and ensure your rule works as intended. To get your rule running in the Orion product's validator, there are additional steps:
- Create strings for the validation message(s) generated by your rule in /javascript/nls/root/problems.js.
- Create a short string describing what your rule does in /javascript/nls/root/messages.js.
- Add an entry to the orion.core.setting declaration in /javascript/plugins/javascriptPlugin.js. This allows your rule to be configured from the JS validator settings page. Make sure it references the same nameKey used in messages.js.
- Add a config entry for your rule to the default ESLint config object in /javascript/validator.js.
- Add your rule to the #updated() handler in /javascript/validator.js.
Reload the JS plugin, and your rule should now be configurable from the Settings page, and properly set up for translation too.
Tests
- Every rule needs extensive unit tests.
- Unit tests should use Mocha.
Running the tests
- To run the ESLint tests as part of the main JavaScript tests suite load {orion-server-url}/javascript/js-tests/JsMochaSuite.html in your web browser.
- To run just the ESLint rule tests, load {orion-server-url}/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Rule%20Tests in your browser.
- To run just the ESLint core tests, load {orion-server-url}/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Core%20Tests in your browser.
- To run only a subset of the tests, add ?grep=ESLint%20Rule%20Tests onto the test page URL.
See Mocha usage options for more options.
User interface
-
Should we have a UI for configuring what rules are active?bug 424268. - 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.- ESLint now has its own syntax for this:
/*eslint ..*/
, which we are using instead.
- ESLint now has its own syntax for this:
i18n
We need to support i18n. Pre-req is bug 422278 (orion.edit.validator support for i18n).