Introduction

This module is intended for parsing connection strings in a manner that is consistent with .NET's DbConnectionStringBuilder class.

The syntax of a connection string appears quite simple at first glance, and consists of a list of key-value pairs separated by semicolons:

>>> toList <$> parse "key=value; key2 = value2" Right [("key","value"),("key2","value2")] 

However, the format can be more complicated than expected.

Examples

A value may be single-quoted (single quotes can be escaped inside a single-quoted string by doubling them):

>>> toList <$> parse "squote='value with '' quotes'" Right [("squote","value with ' quotes")] 

Or double-quoted (double quotes can also be escaped inside a double-quoted string by doubling them):

>>> let (Right quoted) = parse "dquote=\"value with \"\" quotes\"" >>> toList quoted [("dquote","value with \" quotes")] >>> quoted "dquote='value with \" quotes'" 

• - ^ TODO: Note that this is for exact compatibility

Quotes of both kinds may be present in keys:

>>> toList <$> parse "'quote\"=value" Right [("'quote\"","value")] 

Whitespace is ignored everywhere except in quoted strings and inside keys or unquoted values:

>>> toList <$> parse "; a key = v v\t\n;\t key 2 = \"v v\"\n;\t key 3 = 'v v'; " Right [("a key","v v"),("key 2","v v"),("key 3","v v")] 

Equals signs may be escaped in keys by doubling them:

>>> toList <$> parse "1==2=false" Right [("1=2","false")] 

Keys are case-insensitive (and converted to lower-case on output):

>>> toList <$> parse "BIG=small" Right [("big","small")] 

Later values override earlier ones:

>>> toList <$> parse "key=value;key=value2" Right [("key","value2")] 

Assigning a key no value will remove it:

>>> toList <$> parse "key=value;key=" Right [] 

However, you can assign an empty value by giving it a quoted value:

>>> toList <$> parse "key=value;key=''" Right [("key","")] 

• - TODO ^ there appears to be a bug here in .NET

On the other hand, not providing a key doesn't make any sense:

>>> parse "key=value;=value" Left "1:11:\nunexpected '='\nexpecting ';', end of input, or white space\n" 

>>> parse "=value" Left "1:1:\nunexpected '='\nexpecting ';', end of input, or white space\n" 

Another quirk is that keys can contain semicolons:

>>> toList <$> parse "key=value;key2;extended=value" Right [("key","value"),("key2;extended","value")] 

This module implements all of these quirks for you!