1 | /**
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2 | * @fileoverview Rule to flag the use of empty character classes in regular expressions
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3 | * @author Ian Christian Myers
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4 | */
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5 |
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6 | ;
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7 |
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8 | //------------------------------------------------------------------------------
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9 | // Helpers
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10 | //------------------------------------------------------------------------------
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11 |
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12 | /*
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13 | * plain-English description of the following regexp:
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14 | * 0. `^` fix the match at the beginning of the string
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15 | * 1. `\/`: the `/` that begins the regexp
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16 | * 2. `([^\\[]|\\.|\[([^\\\]]|\\.)+\])*`: regexp contents; 0 or more of the following
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17 | * 2.0. `[^\\[]`: any character that's not a `\` or a `[` (anything but escape sequences and character classes)
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18 | * 2.1. `\\.`: an escape sequence
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19 | * 2.2. `\[([^\\\]]|\\.)+\]`: a character class that isn't empty
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20 | * 3. `\/` the `/` that ends the regexp
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21 | * 4. `[gimuy]*`: optional regexp flags
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22 | * 5. `$`: fix the match at the end of the string
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23 | */
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24 | const regex = /^\/([^\\[]|\\.|\[([^\\\]]|\\.)+])*\/[gimuy]*$/;
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25 |
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26 | //------------------------------------------------------------------------------
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27 | // Rule Definition
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28 | //------------------------------------------------------------------------------
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29 |
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30 | module.exports = {
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31 | meta: {
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32 | docs: {
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33 | description: "disallow empty character classes in regular expressions",
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34 | category: "Possible Errors",
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35 | recommended: true,
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36 | url: "https://eslint.org/docs/rules/no-empty-character-class"
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37 | },
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38 |
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39 | schema: [],
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40 |
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41 | messages: {
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42 | unexpected: "Empty class."
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43 | }
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44 | },
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45 |
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46 | create(context) {
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47 | const sourceCode = context.getSourceCode();
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48 |
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49 | return {
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50 |
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51 | Literal(node) {
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52 | const token = sourceCode.getFirstToken(node);
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53 |
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54 | if (token.type === "RegularExpression" && !regex.test(token.value)) {
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55 | context.report({ node, messageId: "unexpected" });
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56 | }
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57 | }
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58 |
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59 | };
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60 |
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61 | }
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62 | };
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