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regexMisleadingQuantifiers

Reports quantifiers whose minimum implies they must match but whose element can match empty.

✅ This rule is included in the ts logical presets.

Reports quantifiers whose minimum implies they must match but whose element can match empty. These quantifiers are misleading because they suggest a minimum number of matches, but the quantified element can match the empty string, making the effective minimum 0.

Examples

Section titled “Examples”

Optional Element with Fixed Repetition

Section titled “Optional Element with Fixed Repetition”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#5CA7E4;--1:#3A68">8F<(asp ansty="le--0:#7FDBCA;--1:#096E">7<2?sp ansty="le--0:#5CA7E4;--1:#3A68">872{<5}sp ansty="le--0:#D9F5DD;--1:#1111">1<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#5CA7E4;--1:#3A">68<8F(a spans="tyle--0:#7FDBCA;--1:#09">66<88F) spans="tyle--0:#7FDBCA;--1:#09">6E72{<0,5} spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#D6DEEB;--1:#40">3<5}/>

The {5} suggests exactly 5 matches are required, but since a? can match empty, the pattern can match the empty string.

Alternation with Optional Elements

Section titled “Alternation with Optional Elements”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#5CA7E4;--1:#3A68">8F(?<:asp ansty="le--0:#7FDBCA;--1:#096E">7<2?sp ansty="le--0:#5CA7E4;--1:#3A68">872<*|sp ansty="le--0:#5CA7E4;--1:#3A68">87<2+sp ansty="le--0:#5CA7E4;--1:#3A68">872{<4}sp ansty="le--0:#D9F5DD;--1:#1111">1<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#5CA7E4;--1:#3A">688F<(?:a spans="tyle--0:#7FDBCA;--1:#09">66<88Fb spans="tyle--0:#7FDBCA;--1:#09">6E<72*| spans="tyle--0:#5CA7E4;--1:#3A">6<88Fc spans="tyle--0:#7FDBCA;--1:#09">66<88F) spans="tyle--0:#7FDBCA;--1:#09">6E72{<0,4} spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#D6DEEB;--1:#40">3<4}/>

The {4} suggests at least 4 matches, but the a?b* alternative can match empty.

Plus Quantifier on Empty-Matchable Group

Section titled “Plus Quantifier on Empty-Matchable Group”
AEconsB0patteAE< =sp ansty="le--0:#5CA7E4;--1:#3A68">81<1/sp ansty="le--0:#5CA7E4;--1:#3A68">8F<(asp ansty="le--0:#7FDBCA;--1:#096E">7<2?sp ansty="le--0:#5CA7E4;--1:#3A68">87<2+sp ansty="le--0:#D9F5DD;--1:#1111">1<1/sp ansty="le--0:#D6DEEB;--1:#403F">5<3;d ivclassNa="meco">
44AEco61B0pat446<88F spans="tyle--0:#D9F5DD;--1:#11">1<111/ spans="tyle--0:#5CA7E4;--1:#3A">68<8F(a spans="tyle--0:#7FDBCA;--1:#09">66<88F) spans="tyle--0:#7FDBCA;--1:#09">61<111/ spans="tyle--0:#D6DEEB;--1:#40">3<)*/>

The + suggests at least 1 match is required, but a? can match empty.

Options

Section titled “Options”

This rule is not configurable.

When Not To Use It

Section titled “When Not To Use It”

If you use misleading quantifiers intentionally for backtracking behavior, or if you use quantifiers to control iteration count rather than match content, you might want to disable this rule.

Further Reading

Section titled “Further Reading”

Equivalents in Other Linters

Section titled “Equivalents in Other Linters”