Validate expressions

validate checks an expression without evaluating it.

It parses the source, resolves functions and parameters, binds the expression, and verifies that it can be compiled in the requested mode.

Validate an open expression

Open validation is the default. It allows the expression to consume an incoming value.

expressif validate 'upper'
expressif validate 'upper' --open

Use open validation for transformations that will later receive input through evaluate --input or run.

Validate a closed expression

A closed expression must be self-contained and evaluable without an incoming value.

expressif validate '5 | add(3)' --closed

Closed validation is useful for constants, source expressions, and configuration-time computations.

--open and --closed cannot be combined.

Read an expression file

Supply the expression inline or with --file/-f, but not both.

expressif validate --file ./expressions/transform.expr --closed

Files are read as strict UTF-8. Missing, directory, undecodable, empty, and invalid files produce diagnostics on standard error.

Understand validation results

On success, the command returns exit code 0 and writes:

Expression is valid.

Validation catches:

• syntax errors;
• binding failures;
• unknown or unsupported functions;
• missing or unexpected function parameters;
• an input-dependent expression validated as closed.

It does not execute the expression, so it cannot detect failures that depend on a runtime value.

Read diagnostics

Syntax diagnostics identify the source position:

Syntax error [EXPR1001] at line <line>, column <column>:
  <source line>
  ^^^
Unexpected '<token>'.

Binding diagnostics use EXPR2001 and explain what could not be resolved. Several syntax errors are separated by a blank line.

Use validation in continuous integration

Validation is a fast compile gate for checked-in expressions:

expressif validate --file ./expressions/transform.expr --closed
case $? in
  0) echo 'valid' ;;
  2) echo 'invalid expression or invocation' >&2; exit 2 ;;
  1) echo 'unexpected CLI failure' >&2; exit 1 ;;
  *) echo 'unexpected status' >&2; exit 1 ;;
esac

Use inspection when you need to understand how the source was parsed or bound. See Automation and exit codes for the complete stream and status contract.