Explain how to install Prettier plugins when they fail to resolve - #8721
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Prettier v3 loads plugins with a native ESM import() resolved from its current working directory (the workspace) and ignores NODE_PATH. Plugins installed by a pre-command with the default cwd: root are redirected to /node-deps/node_modules, where Prettier never looks, so the install succeeds but the lint still fails with "Cannot find package '...' imported from noop.js". Add a <LINTER_KEY>_ERROR_PLUGIN_NOT_FOUND common_linter_errors entry to the 4 prettier linters. It detects the ESM resolution failures and points to installing the plugins with cwd: workspace, which keeps plain package names in .prettierrc so the same config still works when running Prettier locally without MegaLinter. Fixes #6980
nvuillam
requested review from
Kurt-von-Laven,
bdovaz and
echoix
as code owners
August 12, 2026 07:20
Contributor
✅
|
Contributor
This might be unexpected, I will get back after getting the syntax right |
Contributor
The fix seems to work! |
Member
Author
I'm not sure mega-linter-runner works with standalone images when mentioned in .mega-linter.yml, little bug i should add on my todo ^^ |
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Fixes #6980
Problem
Installing a Prettier plugin via
*_PRE_COMMANDSappears to succeed (added 3 packages), but the lint still fails:Adding
cwd: root— the resolution that works for stylelint and ESLint — does not help either.Root cause
Prettier v3 resolves plugins declared in
.prettierrcwith a native ESMimport(), from a virtualnoop.jsplaced inprocess.cwd()(src/main/plugins/load-plugin.js):MegaLinter runs linters with
cwd= the workspace, so ESM resolution walks/tmp/lint/node_modules→/tmp/node_modules→/node_modules.Two things then collide:
pre_post_factory.complete_command()rewrites anynpm i…pre-command with the defaultcwd: rootintocd /node-deps && npm i…, so the plugin lands in/node-deps/node_modules.NODE_PATH=/node-deps/node_modules, butNODE_PATHis a CommonJS-only mechanism — ESMimport()ignores it entirely.So
/node-deps/node_modulesis invisible to Prettier, which is why the advice that works for stylelint/ESLint (CJSrequire) is exactly wrong for Prettier.Fix
Documentation only — a
<LINTER_KEY>_ERROR_PLUGIN_NOT_FOUNDcommon_linter_errorsentry on the 4 prettier linters (JSON_,YAML_,JAVASCRIPT_,TYPESCRIPT_PRETTIER). It detects the three ESM resolution failure shapes and surfaces the resolution in the failing log, plus a "Known errors and resolutions" section on the generated doc pages.The recommended resolution installs the plugins in the workspace:
This deliberately keeps plain package names in
.prettierrc, so the very same config keeps working when running Prettier locally without MegaLinter. Referencing plugins by absolute/node-deps/...path also works inside the image, but it breaks local runs, so it is explicitly discouraged in the message rather than offered as an alternative.--no-saveleaves an existingpackage.jsonuntouched, andnode_modulesis already in MegaLinter's default excluded directories.Validation
Run against
ghcr.io/oxsecurity/megalinter-only-json_prettier:betawith a workspace declaring"plugins": ["prettier-plugin-toml"]:Cannot find package 'prettier-plugin-toml' imported from /tmp/lint/noop.js(issue reproduced)cwd: rootadded 3 packagesthen same error (matches the report)cwd: workspaceSuccessfully linted all files without errorsThe new message was rendered in the real image by mounting the updated descriptor over
/megalinter-descriptors/json.megalinter-descriptor.yml.Also checked: the regex matches the 3 real failure strings (
Cannot find package,Cannot find module,Directory import … is not supported) and none of normal Prettier output (Checking formatting...,[warn] file, a genuineSyntaxError); all 132 linters still pass the identifier-prefix validation; the 4 descriptors are prettier-clean.Notes
.claude/rules/descriptors.md, which putscommon_linter_errorswith linter-key-prefixed identifiers in the per-descriptor entry rather than the sharedprettier.megalinter-linter.yml.docs/).complete_command()routenpm i prettier-plugin-*to the workspace instead of/node-deps— but that changes pre-command behaviour for everyone, so it is left out of this documentation-only change.