kitchensink
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Dispatch's awesome components and style guide
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JavaScript
/**
* Requires `var` declaration to be on the top of an enclosing scope
*
* Types: `Boolean`
*
* Values:
*
* - `true` specifies that `var` declarations must occur the top of a function scope.
*
* #### Example
*
* ```js
* "requireVarDeclFirst": true
* ```
*
* ##### Valid for mode `true`
*
* ```js
* var x = 1,
* y = 2;
* ```
* ```js
* 'use strict;'
* var x = 1,
* y = 2;
* ```
* ```js
* var x = 1;
* var y = 2;
* ```
* ```js
* var x = 1;
* // comments
* var y = 2;
* ```
* ```js
* var x = 1;
* // comments
* // comments 2
* var y = 2;
* ```
* ```js
* const a = 1;
* const b = 2;
* ```
* ```js
* var x = 1;
* function y() {var z;};
* ```
* ```js
* var x = 1;
* var y = function () {var z;};
* ```
* ```js
* var w = 1;
* function x() {
* var y;
* // comments
* // comments 2
* var z;
* };
* ```
* ```js
* var w = 1;
* function x() {
* "use strict";
* var y;
* };
* ```
* ```js
* var x = 1;
* var y;
* for (y = 0; y < 10; y++) {};
* ```
*
* ##### Invalid
*
* ```js
* var x;
* x = 1;
* var y = 2;
* ```
* ```js
* var w = 1;
* function x() {var y;};
* var z = 2;
* ```
* ```js
* var w = 1;
* function x() {
* var y;
* y = 2;
* var z;
* };
* ```
* ```js
* var a;
* for(var count=0;count < 10;count++){}
* ```
* ```js
* var x;
* for(var count=0;count < 10;count++){
* var y;
* }
* ```
*
*/
var assert = require('assert');
function getVariableScope(node) {
while (node.type !== 'Program' &&
node.type !== 'FunctionDeclaration' &&
node.type !== 'FunctionExpression') {
node = node.parentNode;
}
return node;
}
function getOffsetForBlockStatement(enclosingScope, varDecl, commentTokens, file) {
var offset = 0;
var parentNode = varDecl.parentNode;
if (enclosingScope.type !== 'Program' && parentNode.type === 'BlockStatement') {
offset += 1;
offset += getCommentOffsetBetweenNodes(parentNode, varDecl, commentTokens, file);
}
return offset;
}
function getUseStrictDeclFirst(enclosingScope) {
var firstNode;
if (enclosingScope.type === 'Program') {
firstNode = enclosingScope.body[0];
} else {
firstNode = enclosingScope.body.body[0];
}
if (firstNode.type === 'ExpressionStatement' &&
firstNode.hasOwnProperty('expression') === true &&
firstNode.expression.hasOwnProperty('value') === true &&
firstNode.expression.value === 'use strict') {
return firstNode;
}
return null;
}
function isFirstVarDeclInScope(enclosingScope, varDecl, whitespaceOffsetBeforeVarDecl, commentTokens, file) {
var adjustedVarDeclStart = varDecl.range[0];
var adjustedScopeStart = enclosingScope.range[0];
if (enclosingScope.type !== 'Program') {
// For function declaration and function expression scope use the top block statement as start
// This removes the requirement to offset the function declaration or expression related tokens
adjustedScopeStart = enclosingScope.body.range[0];
// If enclosing scope node type is Program the range start ignores all comments and whitespace before the
// variable declaration
adjustedVarDeclStart -= whitespaceOffsetBeforeVarDecl;
}
adjustedVarDeclStart -= getOffsetForBlockStatement(enclosingScope, varDecl, commentTokens, file);
if (adjustedVarDeclStart === adjustedScopeStart) {
return true;
}
return false;
}
function getCommentOffsetBetweenNodes(previousNode, currentNode, commentTokens, file) {
var count;
var comment;
var commentLength = 0;
for (count = 0; count < commentTokens.length; count++) {
comment = commentTokens[count];
if (comment.range[0] >= currentNode.range[1]) {
// Stop processing comments that are occurred after current node
break;
}
if (previousNode.range[1] < currentNode.range[0] &&
comment.range[0] > previousNode.range[0] &&
comment.range[1] < previousNode.range[1]) {
// Stop processing comments that are within multiple declarators in a single variable declaration
// of the previous node and the previousNode is not the parent of currentNode
break;
}
if (comment.range[0] > currentNode.range[0] &&
comment.range[1] < currentNode.range[1]) {
// Stop processing comments that are within multiple declarators in a single variable declaration
break;
}
if (previousNode.range[0] >= comment.range[1]) {
// Skip comments that occurred before the previous node
continue;
}
commentLength += comment.range[1] - comment.range[0] + file.getWhitespaceBefore(comment).length;
}
return commentLength;
}
function isPreviousNodeAVarDecl(previousNode, varDecl, whitespaceOffsetBeforeVarDecl, commentTokens, file) {
var offsetForComments;
if (varDecl.range[0] === previousNode.range[1]) {
return true;
}
offsetForComments = getCommentOffsetBetweenNodes(previousNode, varDecl, commentTokens, file);
if (varDecl.range[0] - whitespaceOffsetBeforeVarDecl - offsetForComments === previousNode.range[1]) {
return true;
}
return false;
}
module.exports = function() {};
module.exports.prototype = {
configure: function(options) {
assert(
options === true,
this.getOptionName() + ' option requires a true value'
);
},
getOptionName: function() {
return 'requireVarDeclFirst';
},
check: function(file, errors) {
var scopesFoundInFile = {};
var commentTokens = [];
file.iterateTokensByType(['Line', 'Block'], function(commentToken) {
commentTokens.push(commentToken);
});
file.iterateNodesByType(['VariableDeclaration'], function(varDecl) {
// Ignore let and const for now #1783
if (varDecl.kind !== 'var') {
return;
}
var enclosingScope;
var scopeContents;
var previousNode;
var useStrictDirective;
var isVarDeclFirst = false;
var whitespaceOffsetBeforeVarDecl = file.getWhitespaceBefore(file.getFirstNodeToken(varDecl)).length;
enclosingScope = getVariableScope(varDecl.parentNode);
if (!scopesFoundInFile.hasOwnProperty(enclosingScope.range[0])) {
scopesFoundInFile[enclosingScope.range[0]] = { hasNonVarDecl: false, varDecl: [] };
// placing the handling 'use strict' declared as the first statement of scope here to improve
// performance to run once per scope discovered in file
useStrictDirective = getUseStrictDeclFirst(enclosingScope);
if (useStrictDirective !== null) {
// Special case to make varDecl stack contain the use strict as first node
// this reduces the complexity of the isFirstVarDecInScope and reuses
// isPreviousNodeAVarDecl to handle this special scenario
scopesFoundInFile[enclosingScope.range[0]].varDecl.push(useStrictDirective);
}
}
scopeContents = scopesFoundInFile[enclosingScope.range[0]];
if (scopeContents.varDecl.length === 0) {
isVarDeclFirst = isFirstVarDeclInScope(
enclosingScope, varDecl, whitespaceOffsetBeforeVarDecl, commentTokens, file
);
} else {
previousNode = scopeContents.varDecl[scopeContents.varDecl.length - 1];
if (!scopeContents.hasNonVarDecl) {
isVarDeclFirst = isPreviousNodeAVarDecl(
previousNode, varDecl, whitespaceOffsetBeforeVarDecl, commentTokens, file
);
}
}
scopeContents.varDecl.push(varDecl);
if (!isVarDeclFirst) {
scopeContents.hasNonVarDecl = true;
errors.add('Variable declarations must be the first statements of a function scope.',
varDecl.loc.start.line, varDecl.loc.start.column);
}
});
}
};