How to avoid ambiguity – parsing quoted, unquoted and strings containing quotes

I want to able to parse all three variations:

• a string quoted using single quotes, e.g. 'foo'
• a string quoted using double quotes, e.g. "foo"
• a string that contains single/ double quotes, e.g. foo', fo'o, etc.

I have written the following grammar:

@{%
  const appendItem = (a, b) => d => d[a].concat([d[b]]);
%}

subroutines ->
    subroutines _ "|" _ subroutine {% appendItem(0, 4) %}
  | subroutine

subroutine ->
    subroutineName " " parameters {% d => ({subroutine: d[0], values: d[2]}) %}
  | subroutineName {% d => ({subroutine: d[0], values: []}) %}

subroutineName ->
  [a-zA-Z0-9\-_]:+ {% d => d[0].join('') %}

parameters ->
    parameters " " parameter {% appendItem(0, 2) %}
  | parameter

parameter ->
  	sqstring {% id %}
  | dqstring {% id %}
  | nqstring {% id %}

dqstring ->
  "\"" dstrchar:* "\"" {% d => d[1].join('') %}

dstrchar ->
    [^"] {% id %}
  | "\\\"" {% d => '"' %}

sqstring ->
  "'" sstrchar:* "'" {% d => d[1].join('') %}

sstrchar ->
    [^'] {% id %}
  | "\\'" {% d => '\'' %}
  
nqstring ->
  [^| ]:+

_ ->
  [ ]:* {% d => null %}

And testing it using nearley-playground with the following inputs:

• foo "a b
• foo a b"
• foo "a"

However, I cannot figure out how to avoid ambiguity between nqstring and dqstring/ sqstring?

Related issue: https://github.com/gajus/pianola/issues/1

[kach]

Do you mean

subroutine: foo
  - bar["    <---- bar, not foo
  - "]baz

in the test case?

[kach]

I think the right answer here is for you to use a lexer. @tjvr ?