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Graph/regex-capture-split-semantics-mismatch

AntiPattern

Regex Capture & Split Semantics

regex-capture-split-semantics-mismatch

Regex capture groups and splitting behave unexpectedly—group re-capture, lookbehind boundaries, and delimiter placement cause wrong substrings, while upstream split inputs stay unsanitized. At stake: incorrect parsing results and silent data corruption.

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Updated6/29/2026

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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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Split your search term by space (` `) into tokens — Start with the full set of rows and filter it to those rows containing the first token. Tension: apply a filter with the next token until you processed all tokens. Outcome: The Javascript function `reduce` is your friend here.

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z.strictObject() / .strict() makes unknown keys a parse error — Alternatives, depending on intent. Tension: the error message is generic. Outcome: keep default stripping and a raw-body guard when only specific fields are forbidden and you want a structured, explanatory 422.

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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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Remove the flex/flex-wrap layout and rely on normal inline/whitespace behavior for wrapping; ensure spacing uses non-breaking vs normal spaces appropriately (e.g., replace hard spaces with non-breaking spaces only where you want to keep tokens together) so line breaks occur between words rather than mid-word or at leading spaces.

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using !Split and !Join. Tension: It looks a bit horrid but it's definitely doable. Outcome: Resource: !Split.

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I have considered using decodeURIComponent to convert the + back to spaces — const key = decodeURIComponent(event.Records[0].s3.object.key);. Tension: I'm unsure if this is a reliable solution, or if I'm supposed to handle these keys differently. Outcome: convert the + back to spaces.

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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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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).

MATCHESSolution

`{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.

MATCHESSolution

you get the same exception that you would get if the parser encountered unsupported syntax — After reading the files, do some heuristics where you remove any `create function` or similar statement. Tension: I cannot modify these DDL files. Outcome: A pragmatic solution here is to match `create( or replace)? function.*?\\$\\$.*?\\$\\$.*?;` or similar.

MATCHESSolution

a quote needs to be escaped using two quotes — You're using `CSVFormat.DEFAULT` which is based on RFC 4180. Tension: inside a quoted string a quote needs to be escaped. Outcome: the problem is not in your production code, nor in the library, but in your `expected` value.

MATCHESSolution

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.

MATCHESSolution

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`.

MATCHESSolution

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.

MATCHESSolution

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:.

MATCHESSolution

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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Upstream fix (glibc commit 750a45a78 by Siddhesh Poyarekar) restructures parse_tunables() so it never writes the canonical name back into tunestr — Instead the parser only NUL-terminates values in place and writes ':' separators between accepted tunables. Tension: so the write cursor can never exceed the read cursor.

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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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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.

MATCHESSolution

subsequent string operators (`putinterval`, `copy`, `forall`) use that slice — Ghostscript 9.52's `rsearch` PostScript operator. Tension: they read/write far beyond the original buffer.

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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).

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

MATCHESSolution

classic Tags attribute format "<tag1><tag2>" — A streaming StackExchange dump extractor (SaxesParser over Posts.xml). Outcome: changed Posts.xml Tags to pipe-delimited.

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