Spans for nested map values are needlessly multi-line

[kevmoo]

Accessing the span for a node in a nested map renders it (needlessly) multiline if it's the LAST item in a map.

Not an issue for root items, though...

import 'dart:convert';

import 'package:yaml/yaml.dart';

void main() {
  final yaml = loadYaml(const JsonEncoder.withIndent(' ').convert({
    'num': 42,
    'nested': {
      'null': null,
      'num': 42,
    },
    'null': null,
  })) as YamlMap;

  print(yaml.nodes['num'].span.message('hello'));

  final nestedNode = yaml.nodes['nested'] as YamlMap;

  print(nestedNode.nodes['null'].span.message('prints fine. not last'));
  print(nestedNode.nodes['num'].span.message('last value prints multi-line'));

  print(yaml.nodes['null'].span.message('top-level last value prints fine'));
}

output

line 2, column 9: hello
  ╷
2 │  "num": 42,
  │         ^^
  ╵
line 4, column 11: prints fine. not last
  ╷
4 │   "null": null,
  │           ^^^^
  ╵
line 5, column 10: last value prints multi-line
  ╷
5 │     "num": 42
  │ ┌──────────^
6 │ │  },
  │ └─^
  ╵
line 7, column 10: top-level last value prints fine
  ╷
7 │  "null": null
  │          ^^^^
  ╵

[kevmoo]

Fix was reverted in a0ecc98

[adarshm-26]

Hi @kevmoo, the bug seems to be due to scanner returning a token with incorrect span. The _scanPlainScalar moves ahead after finding a blank or break and modifies the 'end' variable responsible for identifying total span of the token. I have tried to break out of the _scanPlainScalar while loop if no plain character is found (adarshm-26@e816122) and it does fix this issue.
Also a beginner contributing to open source, so are there any particular steps I should follow before posting a PR in this repository ?? I messed up the last time 😛 .

[kevmoo]

Include tests, make sure travis is green, that's a good start

[adarshm-26]

The bug is more pronounced when using a raw yaml string,
Code:

import 'package:yaml/yaml.dart';
void main() {
  const dtr = 
  '''
  'nested_0': {
    'nested_1': {
      'nested_2': {
        'n2k1': null
        ,
        'n2k2': a
        ,
        'n2k3':                        4     
      },
      'n1k2': 425
    },
    'n0k2': aval      

                      ,
  }
  'rk2': 44
        ,
  ''';

  final yaml = loadYaml(dtr) as YamlMap;
  final yaml_n1 = yaml.nodes['nested_0'] as YamlMap;
  final yaml_n2 = yaml_n1.nodes['nested_1'] as YamlMap;
  final yaml_n3 = yaml_n2.nodes['nested_2'] as YamlMap;
  print(yaml.nodes['rk2'].span.message('Root last entry span, trailing space upto next line'));
  print(yaml_n1.nodes['n0k2'].span.message('Level 1 nested last entry span, trailing space upto comma(,)'));
  print(yaml_n2.nodes['n1k2'].span.message('Level 2 nested last entry span, trailing space upto curly brace(})'));
  print(yaml_n3.nodes['n2k1'].span.message('Level 3 nested first entry span, trailing space upto comma(,)'));
  print(yaml_n3.nodes['n2k2'].span.message('Level 3 nested mid entry span, trailing space upto comma(,)'));
  print(yaml_n3.nodes['n2k3'].span.message('Level 3 nested last entry span, trailing space upto curly brace(})'));
}

Output

line 16, column 10: Root last entry span, trailing space upto next line
   ╷
16 │     'rk2': 44
   │ ┌──────────^
17 │ └         ,
   ╵
line 12, column 13: Level 1 nested last entry span, trailing space upto comma(,)
   ╷
12 │       'n0k2': aval      
   │ ┌─────────────^
13 │ │ 
14 │ │                       ,
   │ └──────────────────────^
   ╵
line 10, column 15: Level 2 nested last entry span, trailing space upto curly brace(})
   ╷
10 │         'n1k2': 425
   │ ┌───────────────^
11 │ │     },
   │ └────^
   ╵
line 4, column 17: Level 3 nested first entry span, trailing space upto comma(,)
  ╷
4 │           'n2k1': null
  │ ┌─────────────────^
5 │ │         ,
  │ └────────^
  ╵
line 6, column 17: Level 3 nested mid entry span, trailing space upto comma(,)
  ╷
6 │           'n2k2': a
  │ ┌─────────────────^
7 │ │         ,
  │ └────────^
  ╵
line 8, column 40: Level 3 nested last entry span, trailing space upto curly brace(})
  ╷
8 │           'n2k3':                        4     
  │ ┌────────────────────────────────────────^
9 │ │       },
  │ └──────^
  ╵

the spec says - "Flow collections entries are terminated by the "," indicator. The final "," may be omitted". This might imply that their span should extend to the "," indicator, but in its absence it extends upto curly braces. The fix I suggested is wrong in this case, removing the PR. Treating the last entry separately could help.