Fexpr

A Crystal port of ganigeorgiev/fexpr, a filter expression parser that generates AST structures from user input for safe creation of SQL, Elasticsearch, and other queries.

Installation

1. Add the dependency to your shard.yml:

   dependencies:
     fexpr:
       github: rubyattack3r/fexpr
   

2. Run shards install

Usage

require "fexpr"

Basic Example

# Input: "id > 1"
result = Fexpr.parse("id > 1")
# => [ExpressionGroup.new(
#   item: Expression.new(
#     left: Token.new(type: TokenType::Identifier, literal: "id"),
#     operation: SignOperation::SignGt,
#     right: Token.new(type: TokenType::Number, literal: "1")
#   ),
#   join: JoinOperation::JoinAnd
# )]

Supported Operators

• Comparison Operators:

  • = Equal
  • != NOT Equal
  • > Greater than
  • >= Greater than or equal
  • < Less than
  • <= Less than or equal
  • ~ Like/Contains
  • !~ NOT Like/Contains

• Array Operators:

  • ?= Array/Any equal
  • ?!= Array/Any NOT Equal
  • ?> Array/Any Greater than
  • ?>= Array/Any Greater than or equal
  • ?< Array/Any Less than
  • ?<= Array/Any Less than or equal
  • ?~ Array/Any Like/Contains
  • ?!~ Array/Any NOT Like/Contains

• Logical Operators:

  • && AND join operator
  • || OR join operator
  • () Parenthesis for grouping

Token Types

Numbers

Number tokens can be integer or decimal numbers:

"123"    # Integer
"10.50"  # Decimal
"-14"    # Negative

Identifiers

Identifiers start with a letter, _, @ or # and can contain letters, digits, . or ::

"id"                     # Simple identifier
"a.b.c"                  # Nested field
"field123"               # With numbers
"@request.method"        # With @ prefix
"author.name:length"     # With modifier

Quoted Text

Text can be wrapped in single or double quotes:

"'Lorem ipsum dolor 123!'"        # Single quotes
"\"escaped \\\"word\\\"\""        # Escaped quotes
"\"mixed 'quotes' are fine\""     # Mixed quotes

Comments

Single line comments start with // and are ignored by the parser:

"// This is a comment"

Contributing

1. Fork it (https://github.com/rubyattack3r/fexpr/fork)
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• rubyattack3r - creator and maintainer