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Orion 5.0 will replace our current JSLint validator with [https://github.com/nzakas/eslint/ ESLint]. This page captures ongoing issues.
+
Orion 5.0 introduced [https://github.com/nzakas/eslint/ ESLint] as the validator that ships with Orion. This page captures ongoing issues.
  
 
== Rules ==  
 
== Rules ==  
Here's a table showing the equivalent validation rules in JSLint and ESLint. Rules that JSLint does not support are marked as Unsupported.  
+
The following sections describe all of the rules currently available in Orion and ones that we plan to add in the future.
  
{| class="wikitable" border="1" style="width: 100%;"
+
=== Potential Programming Problems ===
! ESLint rule
+
These rules report about problems with your code that might have undesired or incorrect results. Warnings from these
! JSLint option
+
rules should be addressed.
! JSLint message
+
! Details
+
|-
+
  
| block-scoped-var
+
{| class="wikitable" border="1" cellpadding="5" cellspacing="0" style="width: 100%;"
| Always on
+
! width=12% | Rule
| '''{variable}' is already defined.''
+
! width=6% | Default Severity
|
+
! width=5% | Available Since
* Occurs when a function-scoped variable is treated as if it was block scoped.
+
! width=35%| Problem Message
* ESLint calls this error '{variable} used outside of binding context.'
+
! width=40% | Details
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455253 no-comma-dangle]
| brace-style
+
| Ignore
| Unsupported
+
|style="text-align:center;"| 8.0
|  
+
| ''Trailing commas in object expressions are discouraged.''
|  
+
| Flags trailing commas in object expressions.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455250 no-cond-assign]
| camelcase
+
| Error
| Unsupported
+
|style="text-align:center;"| 8.0
|
+
| ''Expected a conditional expression and instead saw an assignment.''
|
+
|-
+
 
+
| complexity
+
| Unsupported
+
+
|
+
|-
+
 
+
| consistent-this
+
| Unsupported
+
+
|
+
|-
+
 
+
| curly
+
| Always on
+
|
+
* ''Statement body should be inside '{ }' braces.'' (Orion)
+
* ''Expected '{'.'' (Regular JSLint)
+
|
+
|-
+
 
+
| dot-notation
+
| '''sub'''
+
| ''{a} is better written in dot notation.''
+
|
+
|-
+
 
+
| eqeqeq
+
| '''eqeqeq''' or '''eqeq'''
+
|
+
* ''Expected '===' and saw '=='.''
+
* ''Expected '!==' and saw '!='.''
+
|
+
* Newer versions of JSLint call this option '''eqeqeq'''.
+
* Orion's version calls it '''eqeq''', and inverts the flag's value.
+
|-
+
 
+
| guard-for-in
+
| '''forin'''
+
| ''The body of a <code>for in</code> should be wrapped in an <code>if</code> 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 <code>new Whatever</code>
+
|-
+
 
+
| 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 <code>arguments.callee</code> and <code>arguments.caller</code>.
+
|-
+
 
+
| no-catch-shadow
+
| Always on
+
| '''{a}' is already defined.''
+
|
+
* Flags a <code>catch</code> clause's variable that shadows a variable declared in an outer scope. (In IE8 this [weblog.bocoup.com/the-catch-with-try-catch/ causes the outer variable to be overwritten]).
+
|-
+
 
+
| no-comma-dangle
+
| Always on
+
| ''Unexpected comma.''
+
| Flags trailing commas in object literals.
+
|-
+
 
+
| no-cond-assign
+
| Unsupported
+
|
+
 
| Flags assignment in an <code>if/while/do..while/for</code> condition.
 
| Flags assignment in an <code>if/while/do..while/for</code> condition.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455371 no-console]
| no-console
+
| Error
| '''devel'''
+
|style="text-align:center;"| 8.0
|  
+
| ''Discouraged use of console in browser-based code.''
|
+
| Flags the use of console in browser-based code
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455680 no-constant-condition]
| no-control-regex
+
| Error
| Unsupported
+
|style="text-align:center;"| 8.0
|  
+
| ''Discouraged use of constant as a conditional expression.''
| Flags control characters (U+0000–U+001F and U+007F) within the source argument to the RegExp constructor.
+
| Flags the use of a constant as a conditional expression
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429690 no-debugger]
| no-debugger
+
| Warning
| '''debug'''
+
|style="text-align:center;"| 6.0
| ''All 'debugger' statements should be removed.''
+
| ''debugger' statement use is discouraged.''
|  
+
| Warns when the <code>debugger</code> keyword is used
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=428430 no-dupe-keys]
| no-delete-var
+
| Error
| Always on
+
|style="text-align:center;"| 6.0
| ''Expected '.' and instead saw ';'.''
+
| ''Duplicate object key '{key}'.''
| Flags an attempt to <code>delete</code> a local variable.
+
|-
+
 
+
| no-div-regex
+
| Always on
+
| ''A regular expression literal can be confused with '/='.''
+
| Flags a regex literal starting with <code>/=</code>
+
|-
+
 
+
| no-dupe-keys
+
| Always on
+
| ''Duplicate key '{a}'.''
+
 
| Flags object literals that contain the same key more than once.
 
| Flags object literals that contain the same key more than once.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=439366 no-empty-block]
| no-else-return
+
| Warning
| Unsupported
+
|style="text-align:center;"| 7.0
|  
+
| ''Empty block should be removed or commented.''
| Flags an <code>else</code> appearing after an <code>if</code> that contains a <code>return</code>.
+
| Flags an empty block like <code>if (something) { }</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=428040 no-extra-semi]
| no-empty-class
+
| Warning
| Always on
+
|style="text-align:center;"| 5.0
| ''Empty class.''
+
| ''Unnecessary semicolon.''
| Flags an empty character class <code>[]</code> within a regular expression.
+
| Warns when a semi colon is found where it is not needed
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429815 no-fallthrough]
| no-empty-label
+
| Error
| Always on
+
|style="text-align:center;" | 6.0
| ''Label '{a}' on statement.''
+
| ''Switch case may be entered by falling through previous case. If intended, add a new comment //$FALL-THROUGH$ on the line above''
| Flags a labeled statement that is not a <code>switch</code>, <code>for</code>, or <code>while</code>.
+
| Flags a fallthrough case within a <code>switch</code> statement, unless it is explicitly commented.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455391 no-regex-spaces]
| no-empty
+
| Error
| Unsupported
+
|style="text-align:center;"| 8.0
|  
+
| ''Avoid using multiple spaces in regular expressions. Use ' {${0}}' instead.''
| Flags an empty block like <code>if (something) { }</code>.
+
| Flags regular expressions that have two or more subsequent spaces.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455354 no-reserved-keys]
| no-eq-null
+
| Error
| Always on
+
|style="text-align:center;"| 8.0
| ''Use '===' to compare with 'null'.''
+
| ''Reserved words should not be used as property keys.''
| JSLint produces a similar warning when comparing against <code>undefined</code>.
+
| Checks to see if a JavaScript reserved word is being used as a property key
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=426723 no-sparse-arrays]
| no-eval
+
| Warning
| '''evil'''
+
|style="text-align:center;"| 8.0
| ''eval is evil.''
+
| ''Sparse array declarations should be avoided.''
 +
| Flags sparse arrays with null elements like <code>var arr = [1, ,2]</code>
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=436986 no-unreachable]
| no-ex-assign
+
| Error
| Always on
+
|style="text-align:center;"| 6.0
| ''Do not assign to the exception parameter.''
+
| ''Unreachable code.''
 +
| Flags statements that occur after a <code>return</code>, <code>throw</code>, etc.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429711 use-isnan]
| no-extra-semi
+
| Error
| Always on
+
|style="text-align:center;"| 6.0
| ''Unnecessary semicolon.''
+
| ''Use the isNaN function to compare with NaN.''
 +
| Warns when a comparison is done against NaN without using the <code>isNaN</code> function
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=447189 valid-typeof]
| no-fallthrough
+
| Error
| Unsupported
+
|style="text-align:center;"| 7.0
|  
+
| ''Invalid typeof comparison.''
| Flags a fallthrough case within a <code>switch</code> statement, unless it is explicitly commented.
+
| Warns when a typeof comparison uses an invalid type.
 
|-
 
|-
 +
|}
  
| no-floating-decimal
+
=== Best Practices ===
| Always on
+
These rules are not necessarily problem with your code, but are warnings that you might be doing something
| ''A {leading, trailing} decimal point can be confused with a dot: '{n}'.''
+
you probably should not be.
| Flags numeric literals that have a leading or trailing decimal point.
+
|-
+
  
| no-func-assign
+
{| class="wikitable" border="1" cellpadding="5" cellspacing="0" style="width: 100%;"
| Unsupported
+
! width=12% | Rule
|  
+
! width=6% | Default Severity
| Flags assignment to a variable that's already bound to a <code>FunctionExpression</code>.
+
! width=5% | Available Since
 +
! width=35%| Problem Message
 +
! width=40% | Details
 
|-
 
|-
  
| no-global-strict
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=428433 block-scoped-var]
| Unsupported
+
| Error
|  
+
|style="text-align:center;" | -
| Flags <code>"use strict"</code> applied to the entire Program.
+
| '''{variable}' is already defined.''
 +
|
 +
* Occurs when a function-scoped variable is treated as if it was block scoped.
 +
* ESLint calls this error '{variable} used outside of binding context.'
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429722 curly]
| no-implied-eval
+
| Ignore
| Always on
+
|style="text-align:center;" | 6.0
| ''Implied eval is evil. Pass a function instead of a string.''
+
| ''Statements should be enclosed in braces.''
| Flags calls to the string-argument form of <code>setTimeout</code> and <code>setInterval</code>, which implicitly perform <code>eval</code>.
+
| Warns when statements should be enclosed in braces, for example <code>if(something) foo();</code>
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=414779 eqeqeq]
| no-iterator
+
| Warning
| Always on
+
|style="text-align:center;" | 5.0
| ''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.''
+
 
|
 
|
 +
* ''Expected '===' and saw '=='.''
 +
* ''Expected '!==' and saw '!='.''
 +
| Warns when <code>==</code> or <code>!=</code> is used
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=460976 no-caller]
| no-mixed-requires
+
| Error
|  
+
|style="text-align:center;" | 9.0
|  
+
| ''arguments.{callee, caller} is deprecated.''
| Flags Node.js <code>require()</code>s that mix different types of requires (core, module, file, computed).
+
| Flags references to <code>arguments.callee</code> and <code>arguments.caller</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429702 no-eval]
| no-multi-str
+
| Ignore
|  
+
|style="text-align:center;" | 6.0
|  
+
| '''eval' function calls are discouraged.''
| Flags use of ES5 multiline string literals.
+
| Warns when the <code>eval()</code> function is used
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461929 no-implied-eval]
| no-native-reassign
+
| Ignore
| Always on
+
|style="text-align:center;" | 6.0
|
+
| ''Implicit 'eval' function calls are discouraged.''
* ''Read only.''
+
| Flags calls to the string-argument form of <code>setTimeout</code> and <code>setInterval</code>, which implicitly perform <code>eval</code>. This rule logic was merged to be part of the <b>no-eval</b> rule.
* ''Bad assignment.'' (if assigning to <code>undefined</code>)
+
| Flags an attempt to reassign a native object like <code>Math</code>, Array, <code>undefined</code>, etc.
+
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=455643 no-iterator]
| no-negated-in-lhs
+
| Error
| Unsupported
+
|style="text-align:center;" | 8.0
|  
+
| ''Discouraged __iterator__ property use.''
|
+
| Flags use of <code>__iterator__</code> as an identifier name or property key.
* Flags a unary <code>!</code> operator applied to the LHS of an in statement, which negates the LHS, not the <code>in</code>.
+
* Eg. <code>(!"key" in {key: 1})</code> (which always evaluates to false), will be flagged.
+
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429817 no-new-array]
| no-new-array
+
| Warning
| Always on
+
|style="text-align:center;" | 6.0
 
| ''Use the array literal notation [].''
 
| ''Use the array literal notation [].''
 
| Flags <code>new Array()</code>.
 
| Flags <code>new Array()</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429817 no-new-func]
| no-new-func
+
| Warning
| Always on
+
|style="text-align:center;" | 6.0
 
| ''The Function constructor is eval.''
 
| ''The Function constructor is eval.''
|  
+
| Flags <code>new Function()</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429817 no-new-object]
| no-new-object
+
| Warning
| Always on
+
|style="text-align:center;" | 6.0
 
| ''Use the object literal notation {}.''
 
| ''Use the object literal notation {}.''
 
| Flags <code>new Object()</code>.
 
| Flags <code>new Object()</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429817 no-new-wrappers]
| no-new-wrappers
+
| Warning
|  
+
|style="text-align:center;" | 6.0
 
| ''Do not use {String, Number, Boolean, Math, JSON} as a constructor.''
 
| ''Do not use {String, Number, Boolean, Math, JSON} as a constructor.''
 
| Flags <code>new</code> applied to any of those.
 
| Flags <code>new</code> applied to any of those.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461848 no-proto]
| no-new
+
| Error
| Always on
+
|style="text-align:center;" | -
| ''Do not use 'new' for side effects.''
+
| Flags uses of <code>new</code> operator in an expression that is not assigned to anything.
+
|-
+
 
+
| no-obj-calls
+
| Partial support
+
| ''Math is not a function..''
+
 
|
 
|
* Flags attempts to call object properties of the global object (<code>Math</code>, <code>JSON</code>) as a function, like <code>Math()</code>.
+
* ''Reserved name '__proto__' should not be assigned.''
* JSLint warns only on <code>Math()</code>.
+
* ''Reserved name '__proto__' should not be used as a key.''
 +
| Flags use of the property <code>__proto__</code> as object keys or in assignments
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=414779 no-redeclare]
| no-octal-escape
+
| Warning
| Always on
+
|style="text-align:center;" | 5.0
| ''Bad escapement.''
+
| Flags octal escapes in strings, for example <code>var x = "Copyright \251";</code>
+
|-
+
 
+
| 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'''
+
|  
+
* ''Unexpected use of '++'''
+
* ''Unexpected use of '--'''
+
|-
+
 
+
| no-proto
+
| Always on
+
|
+
* ''Reserved name '__proto__'.'' (if used as an identifier)
+
* ''Stupid key '{a}'.'' (if used as a key)
+
| Treated as a fatal parse error in JSLint.
+
|-
+
 
+
| no-redeclare
+
| Always on
+
 
| '''{a}' is already defined.''
 
| '''{a}' is already defined.''
 
| Usually results from having two <code>for</code> loops in the same function that share a loop variable declaration like <code>var i=...</code>.
 
| Usually results from having two <code>for</code> loops in the same function that share a loop variable declaration like <code>var i=...</code>.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461850 no-self-compare]
| no-return-assign
+
| Error
| Unsupported
+
|style="text-align:center;" | -
|  
+
| ''Comparing a value to itself has no effect.''
|
+
* Prevents assignment in a <code>return</code> statement.
+
* Unsupported by JSLint, although JSLint does require parens around a return-assignment, eg: <code>return (x = 2);</code>
+
|-
+
 
+
| no-script-url
+
| Always on
+
| ''Script URL.''
+
|
+
* Flags string literals beginning with <code>javascript:</code>. (Script URLs are a form of <code>eval</code>.)
+
* Fatal parse error in JSLint.
+
|-
+
 
+
| no-self-compare
+
| Unsupported
+
|
+
 
| Flags comparisons where the left- and right-hand sides are the same.
 
| Flags comparisons where the left- and right-hand sides are the same.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=438319 no-shadow]
| no-shadow
+
| Warning
| Unsupported
+
|style="text-align:center;" | 8.0
|  
+
| '''{a}' is already declared in the upper scope.''
| Flags variables that have the same name as a variable declared in an outer scope.
+
| Flags variables that have the same name as a variable declared in an upper scope.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461321 no-shadow-global]
| no-spaced-func
+
| Warning
|  
+
|style="text-align:center;" | 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.
 
|-
 
|-
 
+
!style="text-align:left;"| [http://git.eclipse.org/c/orion/org.eclipse.orion.client.git/commit/?id=6e517847ef0742b090130748fb9a0329d33e16bf no-throw-literal]
| no-sync
+
| Warning
| '''stupid'''
+
|style="text-align:center;" | 9.0
| ''Unexpected sync method: '{a}'.''
+
| ''Throw an Error instead.''
|
+
| Flags code that throws a literal, eg. <code>throw "a problem occurred";</code>
* Flags Node.js's synchronous I/O methods.
+
* The '''stupid''' option is supported only in newer versions of JSLint (not Orion's).
+
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=414779 no-undef]
| no-ternary
+
| Error
| Unsupported
+
|style="text-align:center;" | 5.0
|
+
| Flags any use of the ternary operator <code>cond ? thenExpr : elseExpr</code>
+
|-
+
 
+
| no-undef-init
+
| Always on
+
| ''It is not necessary to initialize '{variable}' to 'undefined'.''
+
|  
+
|-
+
 
+
| no-undef
+
| '''undef'''
+
 
| '''{variable}' is not defined.''
 
| '''{variable}' is not defined.''
 
|
 
|
 
* Flags references to a global variable that is not listed in a /*global*/ or /*globals*/ block.
 
* Flags references to a global variable that is not listed in a /*global*/ or /*globals*/ block.
* Predefined environments (eg. '''node''', '''browser''') can be set in the /*jslint */ block.
+
* Predefined environments (eg. '''node''', '''browser''', '''amd''') can be set in a /*eslint-env */ block.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=427310 no-unused-params]
| no-underscore-dangle
+
| Warning
| '''nomen'''
+
|style="text-align:center;" | 6.0
| ''Dangling '_'''
+
| ''Parameter '{param}' is not used.''
 +
| Flags parameters in function declarations / expressions if they are not being used
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=414779 no-unused-vars]
| no-unreachable
+
| Warning
| Always on
+
|style="text-align:center;" | 5.0
| ''Unreachable '{statement}' after '{control flow statement}'.''
+
|
| Flags statements that occur after a <code>return</code>, <code>throw</code>, etc.
+
*'''{a}' is not read.''
 +
*'''{a}' is read-only.''
 +
| Warns when a variable is created and not used (read) or a variable that is read-only is assigned to.
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=414779 no-use-before-define]
| no-unused-expressions
+
| Warning
| Always on
+
|style="text-align:center;" | 5.0
| ''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.''
 
| '''{a}' was used before it was defined.''
 +
| Warns when a variable or function is used before it is defined
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461854 no-with]
| no-with
+
| Warning
| Always on
+
|style="text-align:center;" | -
 
| ''Expected an identifier and instead saw 'with'.''
 
| ''Expected an identifier and instead saw 'with'.''
 
| Treated as fatal parse error in JSLint.
 
| Treated as fatal parse error in JSLint.
 
|-
 
|-
 
+
!style="text-align:left;"| [http://git.eclipse.org/c/orion/org.eclipse.orion.client.git/commit/?id=f61bdaf06ac2f40eaca4daed39520cd60c41f5f3 radix]
| no-wrap-func
+
| Warning
| Always on
+
|style="text-align:center;" | 8.0
| ''Do not wrap function literals in parens unless they are to be immediately invoked.''
+
| ''Missing radix parameter.''
| Flags a parenthesized function literal that is not immediately invoked, eg. <code>(function fun(){})</code>
+
| Warns when parseInt() called without the 2nd parameter (radix).
 
|-
 
|-
 +
|}
  
| one-var
+
=== Code Style ===
| '''onevar'''
+
These rules are not problems in any way but will warn based on certain accepted styles for coding.
| ''Too many var statements.''
+
| Allows only 1 <code>var</code> statement per function.
+
|-
+
  
| quote-props
+
{| class="wikitable" border="1" cellpadding="5" cellspacing="0" style="width: 100%;"
| Unsupported
+
! width=12% | Rule
|  
+
! width=6% | Default Severity
| Requires object literal keys to be quoted with " or '.
+
! width=5% | Available Since
 +
! width=35%| Problem Message
 +
! width=40% | Details
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=424128 missing-doc]
| quotes
+
| Ignore
| Unsupported
+
|style="text-align:center;" | 5.0
|  
+
| ''Missing documentation for function '{name}'.''
| Flags any use of single or double quote marks, depending on setting.
+
| Flags missing documentation nodes on function declarations and function expressions when they appear as object properties
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=424204 missing-doc-items]
| radix
+
| Ignore
| Always on
+
|style="text-align:center;" | -
| ''Missing radix parameter.''
+
| ''Missing '{a}' tag for '{b}'.''  
| Affects parseInt().
+
| Flags missing documentation for parameters, returns, throws, etc on function declarations and function expressions when they appear as object properties
 +
|-
 +
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=428429 missing-nls]
 +
| Ignore
 +
|style="text-align:center;" | -
 +
| ''Non externalized string literal '{a}'.''
 +
| Flags String literals that are not properly NLS'd
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=429801 new-parens]
| regex-spaces
+
| Error
| Always on
+
|style="text-align:center;" | 6.0
| ''Spaces are hard to count. Use {n}.''
+
| ''Missing parentheses invoking constructor.''
 +
| Flags <code>new Whatever</code>
 +
|-
 +
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=438095 no-jslint]
 +
| warning
 +
|style="text-align:center;" | 7.0
 +
| ''The 'jslint' directive is unsupported, please use eslint-env.''
 +
| Flags use of the /* jslint */ directive
 
|-
 
|-
 
+
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=425200 no-mixed-returns]
| semi
+
| Error
| Always on
+
|style="text-align:center;" | -
 +
| ''Mixed return types should be avoided.''
 +
| Flags functions that return more than one kind of item, for example returning String and Object
 +
|-
 +
!style="text-align:left;"| [https://bugs.eclipse.org/bugs/show_bug.cgi?id=461852 no-undef-init]
 +
| Warning
 +
|style="text-align:center;" | -
 +
| ''It is not necessary to initialize '{variable}' to 'undefined'.''
 +
| Warns when an explicit assignment to undefined is done, for example <code>var foo = undefined;</code>
 +
|-
 +
!style="text-align:left;" | [https://bugs.eclipse.org/bugs/show_bug.cgi?id=427930 semi]
 +
| Warning
 +
|style="text-align:center;" | 5.0
 
| ''Missing semicolon.''
 
| ''Missing semicolon.''
|
+
| Warns when a semicolon should be used but is not
 
|-
 
|-
 +
|}
  
| strict
+
== Implementing a new rule ==
| '''strict'''
+
''This section explains how to implement a new linting rule. For brevity, all paths are given relative to <tt>bundles/org.eclipse.orion.client.javascript/web/</tt> in the client repo.''
|
+
| Flags any code that lacks the <code>"use strict"</code> pragma.
+
|-
+
  
| unnecessary-strict
+
First, create the tests and rule:
| Unsupported
+
# Create a new <tt>describe("{rule-name}")</tt> block in: <tt>/js-tests/javascript/eslintRuleTests.js</tt>. Add several tests to it.
|
+
# [[#Running the tests|Run the JS bundle tests]] and ensure that your new tests fail.
| Flags <code>"use strict"</code> on a function when the entire Program is already in strict mode.
+
# Implement the actual logic for your rule in <tt>/eslint/lib/load-rules-async.js</tt>.
|-
+
# Run the tests again. This time they should all pass.
  
| use-isnan
+
To get your rule running in the Orion product's validator, there are additional steps:
| Always on
+
# Create strings for the validation message(s) generated by your rule in <tt>/javascript/nls/root/problems.js</tt>.
| ''Use the isNaN function to compare with NaN.''
+
# Create a short string describing what your rule does in <tt>/javascript/nls/root/messages.js</tt>.
|-
+
# Add an entry to the <tt>orion.core.setting</tt> declaration in <tt>/javascript/plugins/javascriptPlugin.js</tt>. This allows your rule to be configured from the JS validator settings page. Make sure it references the same <tt>nameKey</tt> used in <tt>messages.js</tt>.
 +
# Add a config entry for your rule to the default ESLint config object in <tt>/javascript/validator.js</tt>.
 +
# Add your rule to the #updated() handler in <tt>/javascript/validator.js</tt>.
  
| wrap-iife
+
Reload the JS plugin, and your rule should now be configurable from the Settings page, and properly set up for translation too.
| '''immed'''
+
|
+
* ''Wrap the entire immediate function invocation in parens.''
+
* ''Move the invocation into the parens that contain the function.''
+
| Flags missing parens on immediately-invoked functions, eg. <code>function(){ console.log('hi'); }();</code>
+
|-
+
  
| wrap-regex
+
== Tests ==
| Always on
+
* Every rule needs extensive unit tests.
| ''Wrap the /regexp/ literal in parens to disambiguate the slash operator.''
+
* Unit tests should use [http://mochajs.org Mocha].
|-
+
  
 +
=== Running the tests ===
 +
* To run the ESLint tests as part of the main JavaScript tests suite load <tt>{orion-server-url}/javascript/js-tests/JsMochaSuite.html</tt> in your web browser.
 +
** Click [https://orionhub.org/js-tests/javascript/JsMochaSuite.html here] to see the suite running on [https://orionhub.org orionhub].
 +
* To run just the ESLint rule tests, load <tt>{orion-server-url}/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Rule%20Tests</tt> in your browser.
 +
** Click [https://orionhub.org/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Rule%20Tests here] to see the suite running on [https://orionhub.org orionhub].
 +
* To run just the ESLint core tests, load <tt>{orion-server-url}/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Core%20Tests</tt> in your browser.
 +
** Click [https://orionhub.org/js-tests/javascript/JsMochaSuite.html?grep=ESLint%20Core%20Tests here] to see the suite running on [https://orionhub.org orionhub].
 +
* To run only a subset of the tests, add <tt>?grep=ESLint%20Rule%20Tests</tt> onto the test page URL.
  
|}
+
See [http://mochajs.org/#grep-query Mocha usage options] for more options.
 
+
== Rule priority ==
+
Here are the rules we want, grouped by priority:
+
  
==== Critical ====
+
== User interface ==
* no-undef
+
* <del>Should we have a UI for configuring what rules are active?</del> [https://bugs.eclipse.org/bugs/show_bug.cgi?id=424268 bug 424268].
* eqeqeq
+
* Should we try to support <code>.eslintrc</code>? This would be an ideal project-scope setting.
* block-scoped-var
+
* <del>Should we try to honor equivalent JSLint/JSHint flags when possible? For example <code>/*jslint eqeqeq:false */</code> could disable the eqeqeq rule on a per-file basis.</del>
* no-redeclare
+
** ESLint now has its own syntax for this: <code>/*eslint ..*/</code>, which we are using instead.
  
==== Important ====
+
== i18n ==
* guard-for-in
+
<del>We need to support i18n. Pre-req is {{bug|422278}} (orion.edit.validator support for i18n).</del>
* no-unused-vars
+
* no-dupe-keys
+
* no-octal
+
* no-with
+
* radix
+
* wrap-iife
+
  
==== Nice to have ====
+
[[Category:Orion]]
* 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
+
* semi
+

Revision as of 11:49, 18 March 2015

Orion 5.0 introduced ESLint as the validator that ships with Orion. This page captures ongoing issues.

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-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-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
valid-typeof Error 7.0 Invalid typeof comparison. Warns when a typeof comparison uses an invalid type.

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.
  • Occurs when a function-scoped variable is treated as if it was block scoped.
  • ESLint calls this error '{variable} used outside of binding context.'
curly Ignore 6.0 Statements should be enclosed in braces. Warns when statements should be enclosed in braces, for example if(something) foo();
eqeqeq Warning 5.0
  • Expected '===' and saw '=='.
  • Expected '!==' and saw '!='.
Warns when == or != is used
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. Warns when the eval() function is used
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 -
  • Reserved name '__proto__' should not be assigned.
  • Reserved name '__proto__' should not be used as a key.
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-throw-literal Warning 9.0 Throw an Error instead. Flags code that throws a literal, eg. throw "a problem occurred";
no-undef Error 5.0 '{variable}' is not defined.
  • Flags references to a global variable that is not listed in a /*global*/ or /*globals*/ block.
  • Predefined environments (eg. node, browser, amd) can be set in a /*eslint-env */ block.
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
  • '{a}' is not read.
  • '{a}' is read-only.
Warns when a variable is created and not used (read) or a variable that is read-only is assigned to.
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).

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-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 - Missing '{a}' tag for '{b}'. Flags missing documentation for parameters, returns, throws, etc on function declarations and function expressions when they appear as object properties
missing-nls Ignore - Non externalized string literal '{a}'. Flags String literals that are not properly NLS'd
new-parens Error 6.0 Missing parentheses invoking constructor. Flags new Whatever
no-jslint warning 7.0 The 'jslint' directive is unsupported, please use eslint-env. Flags use of the /* jslint */ directive
no-mixed-returns Error - Mixed return types should be avoided. 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'. Warns when an explicit assignment to undefined is done, for example var foo = undefined;
semi Warning 5.0 Missing semicolon. Warns when a semicolon should be used but is not

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:

  1. Create a new describe("{rule-name}") block in: /js-tests/javascript/eslintRuleTests.js. Add several tests to it.
  2. Run the JS bundle tests and ensure that your new tests fail.
  3. Implement the actual logic for your rule in /eslint/lib/load-rules-async.js.
  4. Run the tests again. This time they should all pass.

To get your rule running in the Orion product's validator, there are additional steps:

  1. Create strings for the validation message(s) generated by your rule in /javascript/nls/root/problems.js.
  2. Create a short string describing what your rule does in /javascript/nls/root/messages.js.
  3. 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.
  4. Add a config entry for your rule to the default ESLint config object in /javascript/validator.js.
  5. 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.

i18n

We need to support i18n. Pre-req is bug 422278 (orion.edit.validator support for i18n).

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