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Add string predicates startsWith, endsWith and contains #78
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Thanks for the suggestion!
To give you some insight about what happens under the hood in the CodeQL engine,
matches("...%")gets translated into an operation likestartsWith("..."), and similarlymatches("%...")becomesendsWith("..."). So the engine is already doing that optimisation for you. Usingmatchesin this way is indeed preferable overindexOf, becauseindexOfhas to produce all(character, index)pairs.This isn't high on our list of priorities, but I agree that either exposing
startsWith/endsWithprimitives, or updating the docs formatchesto clearly describe this case, is a good way to convey the intention.Reacted by Marcono1234- changed the title
[-]Add `string` predicates `startsWith` and `endsWith`[/-][+]Add `string` predicates `startsWith`, `endsWith` and `contains`[/+]on Sep 7, 2021 A
contains(string)predicate would be useful as well, have added it to the description.Reacted by BobbyTRU
What do you think about adding predicates to the CodeQL type
stringfor determining whether a string has a given prefix or suffix or contains a substring? For examplestartsWith(string),endsWith(string)andcontains(string).Currently the workarounds are using
indexOf(...) = 0ormatches(...%)(which seems to be faster thanindexOf, see github/codeql#6479 (comment)). However, these predicates do not convey the intention as clearly, might not be that performant and formatchesone must take care not to accidentally use%or_where the intention was to match them literally.In the github/codeql repository (at github/codeql@3953331) there are at least:
startsWithcould be used(I searched for the regex
matches\("[^%_]*%"\)in CodeQL source files)endsWithcould be used(I searched for the regex
matches\("%[^%_]*"\)in CodeQL source files)