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Case sensitivity

Whether two identifiers that differ only in case (Motor vs motor) are the same symbol is dialect-dependent. plc-st-review makes it configurable with one top-level key in .plc-st-review.yml:

case_sensitive: false   # default

Which value matches your toolchain?

Toolchain Setting Why
Generic IEC 61131-3 (per the standard) false (default) The standard specifies identifiers are case-insensitive.
CODESYS (and CODESYS-derived IDEs) false CODESYS folds identifiers case-insensitively.
Beckhoff TwinCAT false Same as CODESYS / standard.
B&R Automation Studio true B&R treats Motor and motor as two distinct variables.

Pick the value that matches the IDE your code is compiled in. Setting it the wrong way can either hide real bugs (too loose) or invent false ones (too strict).

What it changes

false — case-insensitive (default)

The engine treats identifiers that differ only in case as the same symbol — same as the IEC standard, same as CODESYS / TwinCAT.

  • A constant declared MaxCount is resolved when referenced as MAXCOUNT, so checks like DIVISION_BY_ZERO and LOOP_BOUNDS_REVERSED can read its value.
  • A local level shadowing a global Level fires VARIABLE_SHADOWING.
  • A standard timer parameter written pt := T#5s is found by TIMER_PT_ZERO / TIMER_VALUE_CHANGED even though their lookup spells it PT.
  • An enum value renamed case-only (idle → IDLE) is not flagged by ENUM_VALUE_REMOVED — it's still the same value.
  • IDENTIFIER_CASE_MISMATCH fires to flag references whose case drifted from the declaration (e.g. iCount declared, ICOUNT used).

true — case-sensitive (B&R)

Identifiers are matched exactly. A different case is a different (or undefined) symbol, not a style slip.

  • VARIABLE_SHADOWING only fires on an exact-case match between the local and the global.
  • An enum value renamed case-only (idle → IDLE) is reported as a removal — it really is a different value in this dialect.
  • IDENTIFIER_CASE_MISMATCH is automatically disabled in this mode. The right check for a case-different reference is "is this an undefined symbol?", not a style nit.

Example

# .plc-st-review.yml — for a B&R Automation Studio project
case_sensitive: true

# .plc-st-review.yml — for a TwinCAT or CODESYS project (or omit the key entirely)
case_sensitive: false

The same setting drives every identifier comparison in the engine — globals, enums, named call arguments, scope lookups — so insertion and lookup always agree.