ANTLR rules to match unquoted or quoted multiline string

Question

I would like my grammar to be able to match either a single line string assignment terminated by a newline (\r\n or \n), possibly with a comment at the end, or a multiline assignment, denoted by double quotes. So for example:

key = value
key = spaces are allowed
key = until a new line or a comment # this is a comment
key = "you can use quotes as well" # this is a comment
key = "and
with quotes 
you can also do 
multiline"

Is that doable? I've been bashing my head on this, and got everything working except the multiline. It seems so simple, but the rules simply won't match appropriately.

Add on: this is just a part of a bigger grammar.

Answer 1

Looking at your example input:

# This is the most simple configuration
title = "FML rulez"

# We use ISO notations only, so no local styles
releaseDateTime = 2020-09-12T06:34

# Multiline strings
description = "So,
I'm curious 
where this will end."

# Shorcut string; no quotes are needed in a simple property style assignment
# Or if a string is just one word. These strings are trimmed.
protocol = http

# Conditions allow for overriding, best match wins (most conditions)
# If multiple condition sets equally match, the first one will win.
title[env=production] = "One config file to rule them all"
title[env=production & os=osx] = "Even on Mac"

# Lists
hosts = [alpha, beta]

# Hierarchy is implemented using groups denoted by curly brackets
database {

    # indenting is allowed and encouraged, but has no semantic meaning
    url = jdbc://...
    user = "admin"

    # Strings support default encryption with a external key file, like maven
    password = "FGFGGHDRG#$BRTHT%G%GFGHFH%twercgfg"

    # groups can nest
    dialect {
        database = postgres
    }
}

servers {
    # This is a table:
    # - the first row is a header, containing the id's
    # - the remaining rows are values
    | name     | datacenter | maxSessions | settings                    |
    | alpha    | A          | 12          |                             |
    | beta     | XYZ        | 24          |                             |
    | "sys 2"  | B          | 6           |                             |
    # you can have sub blocks, which are id-less groups (id is the column)
    | gamma    | C          | 12          | {breaker:true, timeout: 15} |
    # or you reference to another block
    | tango    | D          | 24          | $environment                |
}

# environments can be easily done using conditions
environment[env=development] {
    datasource = tst
}
environment[env=production] {
    datesource = prd
}

I'd go for something like this:

grammar TECL;

input_file
 : configs EOF
 ;

configs
 : NL* ( config ( NL+ config )* NL* )?
 ;

config
 : property
 | group
 | table
 ;

property
 : WORD conditions? ASSIGN value
 ;

group
 : WORD conditions? NL* OBRACE configs CBRACE
 ;

conditions
 : OBRACK property ( AMP property )* CBRACK
 ;

table
 : row ( NL+ row )*
 ;

row
 : PIPE ( col_value PIPE )+
 ;

col_value
 : ~( PIPE | NL )*
 ;

value
 : WORD
 | VARIABLE
 | string
 | list
 ;

string
 : STRING
 | WORD+
 ;

list
 : OBRACK ( value ( COMMA value )* )? CBRACK
 ;

ASSIGN : '=';
OBRACK : '[';
CBRACK : ']';
OBRACE : '{';
CBRACE : '}';
COMMA  : ',';
PIPE   : '|';
AMP    : '&';

VARIABLE
 : '$' WORD
 ;

NL
 : [\r\n]+
 ;

STRING
 : '"' ( ~[\\"] | '\\' . )* '"'
 ;

WORD
 : ~[ \t\r\n[\]{}=,|&]+
 ;

COMMENT
 : '#' ~[\r\n]* -> skip
 ;

SPACES
 : [ \t]+ -> skip
 ;

which will parse the example in the following parse tree:

And the input:

key = value
key = spaces are allowed
key = until a new line or a comment # this is a comment
key = "you can use quotes as well" # this is a comment
key = "and
with quotes 
you can also do 
multiline"

into the following:

For now: multiline quoted works, spaces in unquoted string not.

As you can see in the tree above, it does work. I suspect you used part of the grammar in your existing one and that doesn't work.

[...] and am I the process inserting the actions.

I would not embed actions (target code) inside your grammar: it makes it hard to read, and making changes to the grammar will be harder to do. And of course, your grammar will only work for 1 language. Better use a listener or visitor instead of these actions.

Good luck!