Module expression 

Expression parsing for computed values in ceremony DSL.

This module provides types and functions for parsing pipeline expressions that compute values at runtime, such as ${artifact.ksr | sha256 | hex}.

Syntax

Expressions use Unix-style pipes:

${artifact.ksr | sha256 | hex}
${artifact.keypair.public | fingerprint | hex | upper}
${concat(artifact.a | sha256, artifact.b | sha256) | hex}

Design Principles

• Bytes-first: Hash functions return raw bytes; encoding is explicit
• Left-to-right: Data flows through transformations naturally
• Safe: All functions are total and terminate (no user-defined functions)

Grammar

The formal grammar is documented in docs/dsl/grammar.md (not yet published).

Structs

InvalidExpression

A ${...} occurrence that does not parse as an expression.

LocatedExpression

An expression with its location in the source string.

PipeStage

A stage in a pipeline.

Reference

A reference to a ceremony value: ${type.name} or ${type.name.property}.

Enums

ExprError

Why a ${...} occurrence is not a usable expression.

ExprValue

A value that may contain deferred expressions (parsed, not yet evaluated).

Expression

A parsed expression from ceremony YAML.

Literal

A literal value in an expression.

RefType

The type/namespace of a reference.

StringPart

A part of an interpolated string.

Value

A runtime value in the expression system.

Functions

find_expressions

Find all expressions in a string.

find_invalid_expressions

Find every ${...} in s that does not parse as an expression.

parse_expr_value

Parse a JSON value into an ExprValue, extracting all ${...} expressions.

parse_expression

Parse an expression string.

parse_expression_detailed

Parse an expression string, reporting why it is not one.