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prettier

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Prettier is the industry-standard opinionated code formatter that brings consistency to YAML files by enforcing a unified style across projects. It eliminates formatting debates by automatically reformatting code according to its proven formatting principles.

Key Features:

  • Opinionated Formatting: Zero-configuration approach with sensible defaults that work well for most projects
  • Consistent Output: Deterministic formatting ensures identical results regardless of environment or developer
  • YAML Optimization: Specialized handling of YAML syntax including proper indentation, spacing, and structure
  • Multi-Language Support: Part of a comprehensive formatting ecosystem covering 20+ languages
  • Parse Safety: Validates that formatted code maintains semantic equivalence to the original
  • Configuration Flexibility: Supports project-specific settings through .prettierrc files when customization is needed
  • Fast Performance: High-speed formatting suitable for large YAML files
  • Team Standardization: Eliminates style discussions and ensures consistent formatting across team members

prettier documentation

prettier - GitHub

Configuration in MegaLinter

Variable Description Default value
YAML_PRETTIER_ARGUMENTS User custom arguments to add in linter CLI call
Ex: -s --foo "bar"
YAML_PRETTIER_COMMAND_REMOVE_ARGUMENTS User custom arguments to remove from command line before calling the linter
Ex: -s --foo "bar"
YAML_PRETTIER_FILTER_REGEX_INCLUDE Custom regex including filter
Ex: (src\|lib)
⚠️ Not available with YAML_PRETTIER_CLI_LINT_MODE = project		 Exclude no file
YAML_PRETTIER_FILTER_REGEX_EXCLUDE Custom regex excluding filter
Ex: (test\|examples)
⚠️ Not available with YAML_PRETTIER_CLI_LINT_MODE = project		 Exclude no file
YAML_PRETTIER_CLI_LINT_MODE Override default CLI lint mode
- file: Calls the linter for each file
- list_of_files: Call the linter with the list of files as argument
- project: Call the linter from the root of the project		 list_of_files
YAML_PRETTIER_FORWARD_EXCLUDED_DIRECTORIES In project CLI lint mode, forward excluded directories (EXCLUDED_DIRECTORIES + ADDITIONAL_EXCLUDED_DIRECTORIES) to the linter through its native exclusion arguments or generated ignore/config files true
YAML_PRETTIER_FILE_EXTENSIONS Allowed file extensions. "*" matches any extension, "" matches empty extension. Empty list excludes all files
Ex: [".py", ""]		 [".yml", ".yaml"]
YAML_PRETTIER_FILE_NAMES_REGEX File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files
Ex: ["Dockerfile(-.+)?", "Jenkinsfile"]		 Include every file
YAML_PRETTIER_PRE_COMMANDS List of bash commands to run before the linter None
YAML_PRETTIER_POST_COMMANDS List of bash commands to run after the linter None
YAML_PRETTIER_UNSECURED_ENV_VARIABLES List of env variables explicitly not filtered before calling YAML_PRETTIER and its pre/post commands None
YAML_PRETTIER_CONFIG_FILE prettier configuration file name
Use LINTER_DEFAULT to let the linter find it		 .prettierrc.json
YAML_PRETTIER_RULES_PATH Path where to find linter configuration file Workspace folder, then MegaLinter default rules
YAML_PRETTIER_DISABLE_ERRORS Run linter but consider errors as warnings true
YAML_PRETTIER_DISABLE_ERRORS_IF_LESS_THAN Maximum number of errors allowed 0
YAML_PRETTIER_TIMEOUT_SECONDS Maximum duration in seconds of the linter run, after which the linter process and its child processes are killed and reported as an error (exit code 124). Overrides LINTER_TIMEOUT_SECONDS. 0 disables the timeout 300
YAML_PRETTIER_CLI_EXECUTABLE Override CLI executable ['prettier']

IDE Integration

Use prettier in your favorite IDE to catch errors before MegaLinter !

IDE Extension Name Install
Emacs prettier-emacs Visit Web Site
Emacs prettier.el Visit Web Site
Emacs apheleia Visit Web Site
IDEA Prettier
Sublime Text JsPrettier Visit Web Site
vim vim-prettier Visit Web Site
visual_studio JavaScriptPrettier Visit Web Site
Visual Studio Code prettier-vscode Install in VSCode

MegaLinter Flavors

This linter is available in the following flavors

Flavor Description Embedded linters Info
all Default MegaLinter Flavor 132 Docker Image Size (tag) Docker Pulls
c_cpp Optimized for pure C/C++ projects 60 Docker Image Size (tag) Docker Pulls
ci_light Optimized for CI items (Dockerfile, Jenkinsfile, JSON/YAML schemas,XML 23 Docker Image Size (tag) Docker Pulls
cupcake MegaLinter for the most commonly used languages 98 Docker Image Size (tag) Docker Pulls
documentation MegaLinter for documentation projects 53 Docker Image Size (tag) Docker Pulls
dotnet Optimized for C, C++, C# or VB based projects 67 Docker Image Size (tag) Docker Pulls
dotnetweb Optimized for C, C++, C# or VB based projects with JS/TS 83 Docker Image Size (tag) Docker Pulls
formatters Contains only formatters 19 Docker Image Size (tag) Docker Pulls
go Optimized for GO based projects 55 Docker Image Size (tag) Docker Pulls
java Optimized for JAVA based projects 58 Docker Image Size (tag) Docker Pulls
javascript Optimized for JAVASCRIPT or TYPESCRIPT based projects 70 Docker Image Size (tag) Docker Pulls
php Optimized for PHP based projects 58 Docker Image Size (tag) Docker Pulls
python Optimized for PYTHON based projects 70 Docker Image Size (tag) Docker Pulls
ruby Optimized for RUBY based projects 54 Docker Image Size (tag) Docker Pulls
rust Optimized for RUST based projects 54 Docker Image Size (tag) Docker Pulls
salesforce Optimized for Salesforce based projects 58 Docker Image Size (tag) Docker Pulls
swift Optimized for SWIFT based projects 54 Docker Image Size (tag) Docker Pulls
terraform Optimized for TERRAFORM based projects 56 Docker Image Size (tag) Docker Pulls

Behind the scenes

How are identified applicable files

  • File extensions: .yml, .yaml

How the linting is performed

prettier is called once on the whole project directory (project CLI lint mode)

  • filtering can not be done using MegaLinter configuration variables,it must be done using prettier configuration or ignore file (if existing)
  • VALIDATE_ALL_CODEBASE: false doesn't make prettier analyze only updated files

Example calls

prettier --check myfile.yml

prettier --config .prettierrc.json --check myfile.yml

prettier --config .prettierrc.json --write myfile.yml

Help content

Usage: prettier [options] [file/dir/glob ...]

By default, output is written to stdout.
Stdin is read if it is piped to Prettier and no files are given.

Output options:

  -c, --check              Check if the given files are formatted, print a human-friendly summary
                           message and paths to unformatted files (see also --list-different).
  -l, --list-different     Print the names of files that are different from Prettier's formatting (see also --check).
  -w, --write              Edit files in-place. (Beware!)

Format options:

  --arrow-parens <always|avoid>
                           Include parentheses around a sole arrow function parameter.
                           Defaults to always.
  --bracket-same-line      Put > of opening tags on the last line instead of on a new line.
                           Defaults to false.
  --no-bracket-spacing     Do not print spaces between brackets.
  --embedded-language-formatting <auto|off>
                           Control how Prettier formats quoted code embedded in the file.
                           Defaults to auto.
  --end-of-line <lf|crlf|cr|auto>
                           Which end of line characters to apply.
                           Defaults to lf.
  --experimental-operator-position <start|end>
                           Where to print operators when binary expressions wrap lines.
                           Defaults to end.
  --no-experimental-ternaries
                           Default behavior of ternaries; keep question marks on the same line as the consequent.
  --html-whitespace-sensitivity <css|strict|ignore>
                           How to handle whitespaces in HTML.
                           Defaults to css.
  --jsx-single-quote       Use single quotes in JSX.
                           Defaults to false.
  --object-wrap <preserve|collapse>
                           How to wrap object literals.
                           Defaults to preserve.
  --parser <flow|babel|babel-flow|babel-ts|typescript|acorn|espree|meriyah|css|less|scss|json|json5|jsonc|json-stringify|graphql|markdown|mdx|vue|yaml|glimmer|html|angular|lwc|mjml>
                           Which parser to use.
  --print-width <int>      The line length where Prettier will try wrap.
                           Defaults to 80.
  --prose-wrap <always|never|preserve>
                           How to wrap prose.
                           Defaults to preserve.
  --quote-props <as-needed|consistent|preserve>
                           Change when properties in objects are quoted.
                           Defaults to as-needed.
  --no-semi                Do not print semicolons, except at the beginning of lines which may need them.
  --single-attribute-per-line
                           Enforce single attribute per line in HTML, Vue and JSX.
                           Defaults to false.
  --single-quote           Use single quotes instead of double quotes.
                           Defaults to false.
  --tab-width <int>        Number of spaces per indentation level.
                           Defaults to 2.
  --trailing-comma <all|es5|none>
                           Print trailing commas wherever possible when multi-line.
                           Defaults to all.
  --use-tabs               Indent with tabs instead of spaces.
                           Defaults to false.
  --vue-indent-script-and-style
                           Indent script and style tags in Vue files.
                           Defaults to false.

Config options:

  --config <path>          Path to a Prettier configuration file (.prettierrc, package.json, prettier.config.js).
  --no-config              Do not look for a configuration file.
  --config-precedence <cli-override|file-override|prefer-file>
                           Define in which order config files and CLI options should be evaluated.
                           Defaults to cli-override.
  --no-editorconfig        Don't take .editorconfig into account when parsing configuration.
  --find-config-path <path>
                           Find and print the path to a configuration file for the given input file.
  --ignore-path <path>     Path to a file with patterns describing files to ignore.
                           Multiple values are accepted.
                           Defaults to [.gitignore, .prettierignore].
  --plugin <path>          Add a plugin. Multiple plugins can be passed as separate `--plugin`s.
                           Defaults to [].
  --with-node-modules      Process files inside 'node_modules' directory.

Editor options:

  --cursor-offset <int>    Print (to stderr) where a cursor at the given position would move to after formatting.
                           Defaults to -1.
  --range-end <int>        Format code ending at a given character offset (exclusive).
                           The range will extend forwards to the end of the selected statement.
                           Defaults to Infinity.
  --range-start <int>      Format code starting at a given character offset.
                           The range will extend backwards to the start of the first line containing the selected statement.
                           Defaults to 0.

Other options:

  --cache                  Only format changed files. Cannot use with --stdin-filepath.
                           Defaults to false.
  --cache-location <path>  Path to the cache file.
  --cache-strategy <metadata|content>
                           Strategy for the cache to use for detecting changed files.
  --check-ignore-pragma    Check whether the file's first docblock comment contains '@noprettier' or '@noformat' to determine if it should be formatted.
                           Defaults to false.
  --no-color               Do not colorize error messages.
  --no-error-on-unmatched-pattern
                           Prevent errors when pattern is unmatched.
  --file-info <path>       Extract the following info (as JSON) for a given file path. Reported fields:
                           * ignored (boolean) - true if file path is filtered by --ignore-path
                           * inferredParser (string | null) - name of parser inferred from file path
  -h, --help <flag>        Show CLI usage, or details about the given flag.
                           Example: --help write
  -u, --ignore-unknown     Ignore unknown files.
  --insert-pragma          Insert @format pragma into file's first docblock comment.
                           Defaults to false.
  --log-level <silent|error|warn|log|debug>
                           What level of logs to report.
                           Defaults to log.
  --require-pragma         Require either '@prettier' or '@format' to be present in the file's first docblock comment in order for it to be formatted.
                           Defaults to false.
  --stdin-filepath <path>  Path to the file to pretend that stdin comes from.
  --support-info           Print support information as JSON.
  -v, --version            Print Prettier version.

Installation on mega-linter Docker image

  • Dockerfile commands : 
    # Parent descriptor install
# renovate: datasource=npm depName=typescript
ARG NPM_TYPESCRIPT_VERSION=6.0.3
# Linter install
# renovate: datasource=npm depName=prettier
ARG NPM_PRETTIER_VERSION=3.9.6

Known errors and resolutions

When this linter fails for a known non-lint reason (remote service unavailable, malformed config, missing credentials, etc.), MegaLinter detects the pattern below in the linter output and surfaces the matching guidance.

YAML_PRETTIER_ERROR_PLUGIN_NOT_FOUND

Detection pattern (regex):

(Cannot find (package|module) '[^']+' imported from|Directory import '[^']+' is not supported resolving ES modules)

Resolution guidance:

Prettier could not load a plugin declared in the `plugins` array of your `.prettierrc.*` (e.g. `prettier-plugin-toml`, `prettier-plugin-sh`, `@prettier/plugin-xml`).
Prettier v3 loads plugins with a native ESM `import()` resolved from its current working directory, which MegaLinter sets to the workspace. ESM ignores `NODE_PATH`, so plugins installed in MegaLinter's bundled npm root (`/node-deps/node_modules`) are invisible to Prettier, unlike for ESLint or stylelint.
Resolution: install the plugins in the workspace with a pre-command. `cwd: workspace` is required: with the default `cwd: root`, MegaLinter redirects `npm install` to `/node-deps`, where Prettier will not find them.
    YAML_PRETTIER_PRE_COMMANDS:
      - command: npm install --no-save prettier-plugin-toml prettier-plugin-sh
        cwd: workspace
        continue_if_failed: false
If the plugins are already listed in your `package.json`, run `npm ci` (or `npm install`) with the same `cwd: workspace` instead.
Keep plain package names in the `plugins` array of `.prettierrc.*`, so the very same config keeps working when you run Prettier locally without MegaLinter. Do not replace them with absolute `/node-deps/...` paths: those resolve only inside the MegaLinter image.
Also check that each package name matches the published npm package exactly (e.g. `@prettier/plugin-xml`, not `prettier-plugin-xml`).