no-var-redeclaration.md

sfmc/amp-no-var-redeclaration

Disallow re-declaring a variable with var after it has already been declared.

Type	problem
Default severity	warn in recommended; error in strict
Fixable	—

Why This Rule Exists

In AMPscript, re-declaring an already-declared variable with var silently resets its value to null. This is a common source of bugs when code is copy-pasted or blocks are re-ordered — the second var @x statement discards any value assigned in between, leading to unexpected empty output or runtime errors downstream.

Settings

Setting	Values	Default
severity	"error" | "warn" | "off"	"warn"

This rule has no configuration options.

Examples

Not allowed:

%%[
  var @name
  set @name = "Alice"
  var @name
  /* @name is now null */
  output(concat("Hello ", @name))
]%%

Allowed:

%%[
  var @name
  set @name = "Alice"
  output(concat("Hello ", @name))
]%%

When to Disable

// eslint.config.js
rules: { 'sfmc/amp-no-var-redeclaration': 'off' }