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41 lines
1.5 KiB
Markdown
41 lines
1.5 KiB
Markdown
# Negative Look-Ahead Search With ripgrep
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I have a huge monorepo with a bunch of instances of the
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`NEXT_PUBLIC_SANITY_DATASET` env var that need to be updated to
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`NEXT_PUBLIC_SANITY_DATASET_ID` (notice the `_ID` appended to the end). If I do
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a basic search for `NEXT_PUBLIC_SANITY_DATASET`, I get a huge list of results
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cluttered with all the instances where this env var has already been updated.
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To get a list of _only_ the places where the old env var, and not the new env
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var, appear, I need to use [a regex feature called a negative
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look-ahead](https://www.regular-expressions.info/lookaround.html). That looks
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something like `PATTERN(?!NLA)` where we want to match on `PATTERN`, but not if
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it is immediately followed by `NLA`.
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Let's try that with [ripgrep](https://github.com/BurntSushi/ripgrep):
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```bash
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$ rg 'NEXT_PUBLIC_SANITY_DATASET(?!_ID)' --hidden --glob '!node_modules/**' --glob '!.git/**'
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regex parse error:
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NEXT_PUBLIC_SANITY_DATASET(?!_ID)
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^^^
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error: look-around, including look-ahead and look-behind, is not supported
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Consider enabling PCRE2 with the --pcre2 flag, which can handle backreferences
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and look-around.
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```
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It doesn't work as is, but the error message helpfully tells me that I need to
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include the `--pcre2` flag for look-ahead to work.
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Let's try that again:
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```bash
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❯ rg --pcre2 'NEXT_PUBLIC_SANITY_DATASET(?!_ID)' --hidden --glob '!node_modules/**' --glob '!.git/**'
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apps/testing-javascript/.env.development
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37:NEXT_PUBLIC_SANITY_DATASET=production
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...
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```
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That works!
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