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Serge van den Oever
Serge van den Oever

Posted on • Originally published at sergevandenoever.nl

Prevent useless npm error output in your project

#npm

When you write a node script that can be executed through npm, is is convenient to have an error exit code when for example a validation error occurs.

Assume we have an npm script validate as follows:

 "scripts": { "validate": "node validate.js" }
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If we run npm run validate We get output like:

Development mode: false Current working directory: C:\P\competenceframework\packages\content ERROR: C:\P\competenceframework\packages\content\src\competenceframework-settings.json(1,1): SchemaValidationError - rings is not allowed. npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! @competenceframework/content@1.0.0 validate: `validate` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the @competenceframework/content@1.0.0 validate script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above. npm ERR! A complete log of this run can be found in: npm ERR! C:\Users\serge\AppData\Roaming\npm-cache\_logs\2022-02-15T23_23_29_477Z-debug.log npm ERR! code ELIFECYCLE npm ERR! errno 1 npm ERR! competenceframework@1.0.0 validate: `cd packages && cd content && npm run validate` npm ERR! Exit status 1 npm ERR! npm ERR! Failed at the competenceframework@1.0.0 validate script. npm ERR! This is probably not a problem with npm. There is likely additional logging output above. npm ERR! A complete log of this run can be found in: npm ERR! C:\Users\serge\AppData\Roaming\npm-cache\_logs\2022-02-15T23_23_29_526Z-debug.log
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A large part of the error output is useless, it is npm related.

To skip this output use the --silent flag when calling npm:

npm run validate --silent
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The output will now be:

Development mode: false Current working directory: C:\P\competenceframework\packages\content ERROR: C:\P\competenceframework\packages\content\src\competenceframework-settings.json(1,1): SchemaValidationError - rings is not allowed.
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If you run the script from a VSCode task validate, configured in .vscode/tasks.json it is possible to prevent the output as follows using the --silent flag:

{ "version": "2.0.0", "tasks": [ { "label": "Validate", "detail": "Validate all content and parse errors from output", "type": "npm", "script": "validate --silent", "problemMatcher": [ { "owner": "content-linter", "fileLocation": ["autoDetect", "${workspaceFolder}"], "pattern": { "regexp": "^(ERROR|WARNING):\\s*(.*)\\((\\d+),(\\d+)\\):\\s+(.*)$", "file": 2, "line": 3, "column": 4, "severity": 1, "message": 5 } } ], "options": { "statusbar": { "label": "$(check-all) Validate", "color": "#00FF00" } } } ] }
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It is also possible to suppress the npm error output in your project by adding a file .npmrc with the following content:

loglevel=silent
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Using the above configuration the --silent flag is not required in the task configuration.

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