docker-compose.yml报yaml.parser.ParserError块映射解析错误如何解决

报错信息：yaml.parser.ParserError: while parsing a block mapping in "./docker-compose.yml", line 6, column 5 expected , but found '' in "./docker-compose.yml", line 15, column 6

错误成因 #

YAML 语法对缩进要求极其严格，必须使用空格且同层级属性缩进完全一致。本次报错的核心原因是db服务下的networks属性缩进错误：
db节点下的同级属性（image/volumes/restart/environment）统一缩进4个空格，而第15行的networks仅缩进了3个空格，YAML解析器会误认为该属性属于上层的environment块映射，导致映射结构解析失败。

修复方案 #

• 调整db服务下networks属性的缩进，和同层级其他属性保持一致
• 可选：统一规范volumes下挂载路径的缩进，避免后续潜在解析异常

修复后的完整配置如下：

version: '3'

services:
  # Database
  db:
    image: mysql:5.7
    volumes:
      - db_data:/var/lib/mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: password
      MYSQL_DATABASE: wordpress
      MYSQL_USER: wordpress
      MYSQL_PASSWORD: wordpress
    networks:
      - wpsite
  # Wordpress
  wordpress:
    depends_on:
      - db
    image: wordpress:latest
    ports:
      - 8080:80
    restart: always
    volumes: ['./:/var/www/html']
    environment:
      WORDPRESS_DB_HOST: db:3306
      WORDPRESS_DB_USER: wordpress
      WORDPRESS_DB_PASSWORD: wordpress
    networks:
      - wpsite
networks:
  wpsite:
volumes:
  db_data:

内容的提问来源于stack exchange，提问作者Hari Shankar