Guard matches one spelling of many

What goes wrong

A check polices a behaviour by matching a single way of writing it, while the language or platform accepts several equivalent forms. Every other form reaches production unexamined. The reader treats a green guard as coverage of the behaviour, when it only covers the one spelling its author happened to picture.

Example

A rule bans the delete command by name, so the same directory is removed with a plain recursive delete and the gate stays green.

Not to be confused with

Not Substring Check Matches Sibling Word, where a loose pattern matches too much; here the pattern is exact and correct on what it sees, and the miss is the forms it never looks at.

Discovered by

@sks24git GitHub

Field notes · 15

@sks24git2026-11-04

A test guarded a written rule by searching the text for one exact phrase. Rewording the rule in the same meaning breaks the test, and deleting every other clause of the rule keeps it green.

Know what a phrase check can and cannot catch. It pins one sentence, not the rule.
Pin each clause that matters, or test the behaviour the rule drives.

@sks24git2026-11-03beat 2 review rounds

To stop false alarms, a check that a document names only known steps was taught to read fewer phrasings. Each phrasing it no longer reads is a place where a typo now passes in silence.

Fix a guard's false alarms by narrowing what it compares, not what it reads. A miss is silent; an alarm is loud.

@sks24git2026-10-30beat 2 review rounds

A test guarded a speed fix by checking the query text lacked one exact slow form. Any other way to widen the work back to all history still passed, and the page could time out again.

Build the cheap path from the same rule as the result. Then removing the speed-up also changes an answer a test can see.

@sks24git2026-10-28beat 1 review round

A change-based test selector followed imports to find affected tests, but one test loaded a helper by file path. A change to that helper selected nothing on the pull request and only failed later in the merge queue.

Treat a path literal next to a loader call as an import edge. A selector that only follows imports misses every file loaded by path.

@sks24git2026-10-26

A scanner that matched call sites stopped at any character but a space, so an optional call with a question mark before the parenthesis never counted. Every caller written that way vanished from the context.

Test a call scanner on every call syntax. Plain, chained, generic and optional calls each take a different path.

@sks24git2026-10-23beat 1 review round

A ready-made client text rephrased a filing deadline as 'before the payment deadline', but the filing date comes days earlier. A client who files between the two dates is late while the text says they are on time.

Never paraphrase a legal deadline into a relative one. 'Before X' hides the real date; say the date comes from code.

@sks24git2026-10-15

A rule meant to count only code lines skipped test files by naming patterns from one language. Test files from the other half of the codebase got counted as code and pushed small changes over the review threshold.

Check exclusion globs against every naming convention in the repo. One stack's patterns miss the other.
Run the globs over the real tree first. A miss shows up only as a count.

@sks24git2026-09-15beat 4 review rounds

A guard banned one spelling of the delete command inside a block. The same directory can be removed with a plain recursive delete, which the guard never looks for, so the banned behaviour comes back green.

Ban the act, not the invocation. A search for one command name misses every other way to do the same thing.
List the spellings your own file already uses.

@sks24git2026-09-11

A lint rule banned handlers that throw away their promise, but every selector required a braced body, so the one-line form of the same handler passed. The gate reads green and the double submit it exists to stop ships.

Fixture the shapes your rule does not match yet. A control built only from matching cases is green by construction.
A passing gate is a claim, not proof.

@sks24git2026-09-10beat 6 review rounds

A stop added to catch a job calling the runner without being registered matched only the indented spelling of that call. The documented command-line spelling walks straight past it.

Match every spelling a caller is documented to use, or none. A one-spelling guard still reads as coverage.
Your own fixtures list the spellings you forgot.

@sks24git2026-09-10beat 5 review rounds

A guard listed the builder calls that expand to a full column list, and every round found another spelling it had missed. The fourth ended it: a list of bad forms cannot close over an API that keeps growing.

Prefer an allow-list or a compiler check to a list of known-bad spellings.
Three misses in a row is the shape talking, not bad luck — replan instead of patching.

@sks24git2026-09-10beat 2 review rounds

A wiring check refused one literal dependency name, so naming a different path-filtered job instead skipped the pin on most changes. Both entry points still reported success while the prose promised two unfiltered hosts.

Reject the shape, not the example. A blacklist of one spelling is a doorway, and the document beside it will call it a wall.

@sks24git2026-09-10beat 1 review round

A new guard decided by string equality against the bare function spelling. The expression-wrapped form means the same thing to the platform, never matches, and is the form the steps it protects must use.

Match a condition by meaning, not by spelling. A string comparison against one syntax waves through every equivalent one.

@sks24git2026-09-10

A source-scanning guard matched only calls written with a dot receiver. The file that owns the machinery calls it unqualified, so the one place most likely to break the rule is invisible to its own guard.

Test a source scanner against the file most likely to violate it. A pattern tuned on call sites misses the owner.
A fail-open branch inside a fail-closed guard is a hole.

@sks24git2026-09-05

A guard's caller census matched one accessor of a generated table, but the generator also emits a second spelling. Callers using it never enter the census, so the guard stays green over the statement it exists to catch.

Give a census its own known-positive through every spelling the generator emits. A list built from one identifier certifies completeness it cannot see.