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Graph/regex-lookaround-miscapture

AntiPattern

Regex Lookaround Miscaptures

regex-lookaround-miscapture

Regex lookbehind and capturing groups miscapture or retain prior matches because group evaluation is stateful and quantifiers can trigger re-evaluation, causing split logic to fire on unintended delimiters and return wrong substrings.

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Updated6/25/2026

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30 linked nodes

MATCHESSolution

To allow for a case insensitive 'live' search — This allows for partial matching from the beginning of the string. Tension: you may need to further adapt the regular expression. Outcome: adapt the code as follows.

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use a different matcher - like `*ByText` or `*ByTestId` — Testing Library test for a component that uses Tanstack Query. Outcome: `*ByLabelText` matchers actually look for inputs associated with the label.

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Tension: the trap is mixing default (stripping) mode with a post-parse policy check. Outcome: parse AFTER the guard.

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Do expression evaluations in a single line

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If I understand correctly you're looking to prepend `/.attachments/` to any `.png` Markdown link — in Azure wiki. Tension: you could use the pattern `(?https://regex101.com/r/NbyUnq/3 for regex details. Outcome: you could use the pattern.

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for any silent-fallback wrapper around an external LLM / tool call. Tension: A 6-line structured-log addition turns 5,000–50,000 cold-debug tokens into a single grep.

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Use a statically declared matcher array (literal values or direct constant expressions that Next can statically evaluate), or precompute/export the matcher list as a build-time constant and import that directly into `middleware.ts`.

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Strip placeholder underscores from the captured value before setting state/display (e.g., replace /_/g with an empty string in the onChange handler), or otherwise sanitize the masked output.

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Use regex extraction and cast matched numbers to NUMERIC for ordering

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Do you want ILIKE searches? If so, then you should do that. — for searches less than 3 characters. Tension: Maybe you should use `%` but with a different threshold. Outcome: Maybe you should use `%` but with a different threshold.

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source is MongoDB and target is Redshift. Tension: I am unable to get the correct query. Outcome: tried using the regex to remove the string part in the format1.

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Use string splitting for the space-delimited parts (split_part) and a regex to strip the surrounding square brackets from the bracketed token (regexp_replace).

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Fix the regex escaping in importOrder (e.g., use \.(css|scss) correctly within strings) and adjust rule order so the non-relative .css/.scss matcher is applied to those imports last (e.g., exclude/route .*\.(css|scss)$ after the broader patterns).

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`{TM_FILENAME_BASE/(^\\w)|-(\\w)/${1:/capitalize}${2:/capitalize}/g}` — vscode snippets documentation. Tension: The main difference is going to be in the regex to capture 2 different character groups. Outcome: with this we have two regex groupings, denoted by the ( ), that we can then reference.

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My current effort is `(?https://regex101.com/r/hccbUh/1 — For these strings, I want to grab everything between `foo` and `bar`. Tension: haven't found one that works. Outcome: Given this `(?https://regex101.com/r/IAQgB5/1.

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How can I avoid that and not match this `g`? — I want to keep the capturing group in case I have to match a string like `stringMyString`. Tension: I do need that `g` as group 1. Outcome: avoid that and not match this `g`.

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Pass lastIndex - 1 to lastIndexOf() when looking for the previous occurrence

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If you want to avoid that then you need a way to separate that initial line and capture its contents — The main issue to overcome here is that you are treating the first line of your CSV specially. Tension: its contents inform the processing of all the other lines. Outcome: here is where `filter()` comes in, and the fact that lambdas close over their context.

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String[] parts = test.split("((?<=\\))\\s*|(?<=\\d{1,}\\.\\d{2} (DR|CR)))"); — for (String test: tests){. Tension: You could add the case "... or split for any white space preceded by a parenthesis". Outcome: Your regex could be written like this:.

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Instead of splitting you could also match the parts that you want using an alternation — where the alternative starts with `\S` to start the match with a non whitespace character. Tension: to prevent matching empty strings. Outcome: \d+(?:\.\d+)?\h*[DC]R|\S.*?(?=\h*\d+(?:\.\d+)?\h*[DC]R).

MATCHESSolution

You are missing another position to split on, which is the space at the end of `(FEES) ` — Instead of using a capture group `(DR|CR)` you can use a character class `[DC]R`. Tension: you can assert a digit to the right. Outcome: you can use a character class `[DC]R` and in the lookbehind you don't have to match 1 or more digits `\d{1,}` but just matching a digit `\d` would also suffice.

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Use regex boundaries that split before CREATE and after END; when procedures end with END;

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Updated retrieval to use recency, normalized momentum, optional vector similarity, trigram score, live-state bias weights, short-term exclusion, escaped ILIKE parameters, and multiplicative tier boost. — Corrective pass for TypeScript memory subsystem retrieval and daemon resilience. Tension: retrieval scoring omitted recency decay, normalized momentum, live-state retrieval bias, and multiplicative tier boost. Outcome: Added daemon exponential reconnect/backoff with status reporting. Corrected spec constants, extractor error fallback handling, non-padding embedding normalization, partitioned migration DDL, non-null event entity roles, seed data migration, and idempotent markdown memory seed insertion.

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Add state check before XInclude expansion at line 1445 — at line 1445. Outcome: This prevents XInclude expansion code from executing while the reader is in backtracking state.

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The assertion at line 447 (assert(p2 - newstr == newlen)) catches mismatches in debug mode but not release. — reencode_escapes() (lines 406-449): two-pass size calculation with int arithmetic. Tension: The two-pass algorithm uses char_needs_escaping() which is context-sensitive. Outcome: The function is invoked in url_parse() at line 753 with attacker-controlled URL input from HTTP redirects.

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Instead of "required/optional," define Pattern as "the specific recurring structure that appears across multiple manifestations.". Tension: Pattern is specific enough to be testable but abstract enough to apply to other problems. Outcome: Include a pattern _scoring_ rule: "Only include patterns that apply to at least 2–3 other similar problems in the dataset.".

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The fix (commit ed0c7c7e) defines allowed = "-_.!~*'();:&=+$," and scans each character — The fix (commit ed0c7c7e) defines allowed = "-_.!~*'();:&=+$," and scans each character. Tension: This correctly treats ';' as valid userinfo without treating it as a terminator. Outcome: Fix is always component-specific grammar validation, not a combined strpbrk over all component terminators.

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false positives are cheap (dedup catches them), false negatives are expensive (lost knowledge) — Abstract types like Pattern need 3-4 shot examples in the prompt. Tension: When uncertain, extract it. Outcome: downstream dedup will handle false positives.

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Later code at lines 273-274 attempts to write to regarray->start[i] for i >= 1, causing overflow — In regexp.c lines 265-267 within match_regex. Tension: Only allocates 1 element. Outcome: regsize can reach 16 (when max_id is 15).

MATCHESSolution

Add validation to reject any path containing ../ sequences after tilde expansion — after tilde expansion. Outcome: implement proper path normalization that prevents traversal.

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