防止别名后红色素yaml.dump对标识语的评论阻塞

Question

在尝试使用ruamel.yaml加载带有注释和别名的yaml时，我得到了换行符。如何防止这种情况发生？

import ruamel.yaml


yaml_conetent = \
"""
entities:
  leg0: &leg0
    claws:
      leg0claw0: {}
      leg0claw1: {}
  leg1: &leg1
    claws:
      leg1claw0: {}
      leg1claw1: {}
  leg2: &leg2
    claws:
      leg2claw0: {}
      leg2claw1: {}
  leg3: &leg3
    claws:
      leg3claw0: {}
      leg3claw1: {}
anchors:
  cat_with_4_legs: &cat_with_4_legs
    legs:
      leg0: *leg0
      leg1: *leg1
      leg2: *leg2
      leg3: *leg3
cats:
  athena: *cat_with_4_legs      # RED
  ares: *cat_with_4_legs      # WHITE
"""

yaml = ruamel.yaml.YAML()
data = yaml.load(yaml_conetent)
yaml.dump(data, sys.stdout)

，其结果是：

...
cats:
  athena: *cat_with_4_legs
                                # RED
  ares: *cat_with_4_legs
                              # WHITE

预期输出：

...
cats:
  athena: *cat_with_4_legs      # RED
  ares: *cat_with_4_legs      # WHITE

Answer 1

这是ruamel.yaml中的一个bug，目前还不清楚是什么原因造成的。

我建议您现在对输出进行后处理：

import sys
import ruamel.yaml

yaml_str = """\
entities:
  leg0: &leg0
    claws:
      leg0claw0: {}
      leg0claw1: {}
  leg1: &leg1
    claws:
      leg1claw0: {}
      leg1claw1: {}
  leg2: &leg2
    claws:
      leg2claw0: {}
      leg2claw1: {}
  leg3: &leg3
    claws:
      leg3claw0: {}
      leg3claw1: {}
anchors:
  cat_with_4_legs: &cat_with_4_legs
    legs:
      leg0: leg0
      leg1: leg1
      leg2: leg2
      leg3: leg3
cats:
  athena: *cat_with_4_legs      # RED
  ares: *cat_with_4_legs      # WHITE
"""

def fix_alias_comment(s):
    res = []
    alias_line = None
    for line in s.splitlines(True):
        if ': *' in line:
            alias_line = len(line) - 1
            res.append(line)
            continue
        if alias_line is not None and line.startswith(' ' * alias_line):
            res[-1] = res[-1][:-1] + line[alias_line:]
            continue
        res.append(line)
    return ''.join(res)
    
yaml = ruamel.yaml.YAML()
data = yaml.load(yaml_str)
yaml.dump(data, sys.stdout, transform=fix_alias_comment)

这意味着：

entities:
  leg0:
    claws:
      leg0claw0: {}
      leg0claw1: {}
  leg1:
    claws:
      leg1claw0: {}
      leg1claw1: {}
  leg2:
    claws:
      leg2claw0: {}
      leg2claw1: {}
  leg3:
    claws:
      leg3claw0: {}
      leg3claw1: {}
anchors:
  cat_with_4_legs: &cat_with_4_legs
    legs:
      leg0: leg0
      leg1: leg1
      leg2: leg2
      leg3: leg3
cats:
  athena: *cat_with_4_legs      # RED
  ares: *cat_with_4_legs      # WHITE

很丑，但它能完成任务