Option to treat all as a warning (aka eslint only-warn)

[fudom]

It would be great if we could set the linter to treat everything as warning. I can set all my rules to "warn" instead "error". But this is not possible with recommended rules. Otherwise I have to declare every recommended rule again, which makes no sense.

Why only warn?

• Don't waste time thinking or discussing about if it should be an error or a warning, focus on enabling of disabling a rule.

• Warnings look different in editors, this allows you to quickly see that some tweaking is required, but your code still runs (eslint rules generally don't block the code from executing and fatal errors are still reported as error). Often you play with code for debugging etc. Prototyping etc. Blocked by linter is annyoing. Only warn which should be fixed convention.

Later on Git hook and/or CI pipelines we use --error-on-warnings (eslint: --max-warnings=0) because we don't want linter warnings remain. I think this is a good way how to use a linter. The developer is not blocked during coding, but forced to fix the warning before commit.

https://www.npmjs.com/package/eslint-plugin-only-warn

Implementation:

biome.json

{
 "linter": {
    "onlyWarn": true
  }
}

[Conaclos]

We could address this when we will revamp our configuration #689. Notably if we associate the severity level to the group, a user could set the severity level of every group to warn.

[fudom]

Ok, but this needs to cover "recommended" (external) rules. Not just your own. I'm not sure what the revamp will look like or what the plan is. But if you still set rules like "someRule": "error" etc, it could be confusing. It needs to be clear that you can set an option "onlyWarn" (or whatever it's called) that the maximum severity level will be "warn" (override). Levels below that are not affected (e.g. info).

Coming from ESLint, I was looking for a better, modern alternative as the new flat config (breaking change) was a terrible challenge. I think it will be less confusing for ESLint users if Biome uses this (warn-only) like in ESLint.

For inspiration see the tiny code:
https://github.com/bfanger/eslint-plugin-only-warn/blob/main/src/only-warn.js

I haven't switched to Biome yet due to conflicts and config issues. Because it's a larger real project. But it looks very interessting. I will try to use it for our projects. Btw. does it have unit testing or any plant for it. Otherwise I will use Vitest. Another new insteressing thing. Currently I use Jest. But anyway... off topic. ^^

[ematipico]

There's also to note that you're referring to an eslint plugin, maintained by people that might have different opinions from eslint core.

I would like to see other tools that do that, like clippy or Ruff

[AVGVSTVS96]

There's also to note that you're referring to an eslint plugin, maintained by people that might have different opinions from eslint core.

I would like to see other tools that do that, like clippy or Ruff

This is also available as a setting in the ESLint VSCode extension.

"eslint.rules.customizations": [{ "rule": "*", "severity": "warn" }],

[colelawrence]

I also want this feature. I find "error"s in VS Code highly distracting when "errors" in the IDE usually mean "this will not compile" or "this has a bug and will not work".

I would feel excellent about this being a fix for the VS Code extension side, though, since it's entirely about the editing experience for me and my team.

[AVGVSTVS96]

Agreed, I know a lot of people are fine with it as is, but I think this is an essential feature for a linter, and should be prioritized as such.

In my opinion, this should be considered a best/standard practice to visually separate linting and LSP errors. I'm not sure why this isn't the case.

[Conaclos]

I also want this feature. I find "error"s in VS Code highly distracting when "errors" in the IDE usually mean "this will not compile" or "this has a bug and will not work".

Currently, recommended rules emit errors and other rules emit warnings. I personally want to propose the following change for Biome 2.0: rules of the correctness group emit errors and other rules emit warnings. This should satisfy most of the requests and avoid the need for an option to turn errors into warnings. Rules from the correctness group report only invalid code.

[AVGVSTVS96]

I also want this feature. I find "error"s in VS Code highly distracting when "errors" in the IDE usually mean "this will not compile" or "this has a bug and will not work".

Currently, recommended rules emit errors and other rules emit warnings. I personally want to propose the following change for Biome 2.0: rules of the correctness group emit errors and other rules emit warnings. This should satisfy most of the requests and avoid the need for an option to turn errors into warnings. Rules from the correctness group report only invalid code.

That would be better, as long as we can set the Biome extension to display all lint rules as errors.

At the same time, at this point why not make it all configurable by the user? This is pretty subjective so it would be best if it were fully configurable, maybe by rule group.

The ESLint VSC extension has this option:

"eslint.rules.customizations": [{ "rule": "*", "severity": "warn" }],

This would be helpful, so at a glance I can tell if something is a lint rule or a real error that would stop the code from working. But it would also be nice to customize how different groups show up when running biome in the cli.

[pedramardakani]

OK, I know this is definitely nothing more than an ugly temporary solution, but some might find it helpful:

TL;DR

Copy this to reduce severity of most of the rules as warn

{
  "$schema": "https://biomejs.dev/schemas/1.8.3/schema.json",
  "formatter": { "enabled": false },
  "organizeImports": { "enabled": true },
  "linter": {
    "enabled": true,
    "rules": {
      "complexity": {
        "noUselessSwitchCase": "warn",
        "noUselessFragments": "warn",
        "noThisInStatic": "warn",
        "useSimpleNumberKeys": "warn",
        "noUselessCatch": "warn",
        "noEmptyTypeParameters": "warn",
        "noUselessThisAlias": "warn",
        "noUselessConstructor": "warn",
        "noUselessLoneBlockStatements": "warn",
        "useFlatMap": "warn",
        "useRegexLiterals": "warn",
        "noStaticOnlyClass": "warn",
        "useOptionalChain": "warn",
        "noUselessEmptyExport": "warn",
        "noExtraBooleanCast": "warn",
        "noUselessTypeConstraint": "warn",
        "noForEach": "warn",
        "noBannedTypes": "warn",
        "noMultipleSpacesInRegularExpressionLiterals": "warn",
        "noWith": "warn",
        "useLiteralKeys": "warn",
        "noUselessTernary": "warn",
        "noUselessRename": "warn",
        "useArrowFunction": "warn",
        "noExcessiveNestedTestSuites": "warn",
        "noUselessLabel": "warn"
      },
      "correctness": {
        "noUnreachable": "warn",
        "noSetterReturn": "warn",
        "useYield": "warn",
        "noSwitchDeclarations": "warn",
        "noUnusedLabels": "warn",
        "noUnsafeFinally": "warn",
        "noChildrenProp": "warn",
        "useIsNan": "warn",
        "noEmptyPattern": "warn",
        "noInvalidConstructorSuper": "warn",
        "noRenderReturnValue": "warn",
        "noSelfAssign": "warn",
        "noConstAssign": "warn",
        "noFlatMapIdentity": "warn",
        "noStringCaseMismatch": "warn",
        "noPrecisionLoss": "warn",
        "noGlobalObjectCalls": "warn",
        "noUnreachableSuper": "warn",
        "noConstructorReturn": "warn",
        "noNonoctalDecimalEscape": "warn",
        "useJsxKeyInIterable": "warn",
        "noEmptyCharacterClassInRegex": "warn",
        "noInnerDeclarations": "warn",
        "noConstantCondition": "warn",
        "noVoidElementsWithChildren": "warn",
        "noUnsafeOptionalChaining": "warn",
        "useExhaustiveDependencies": "warn",
        "useValidForDirection": "warn",
        "noInvalidUseBeforeDeclaration": "warn",
        "noUnnecessaryContinue": "warn",
        "noVoidTypeReturn": "warn"
      },
      "nursery": {},
      "performance": { "noDelete": "warn", "noAccumulatingSpread": "warn" },
      "security": {
        "noDangerouslySetInnerHtmlWithChildren": "warn",
        "noGlobalEval": "warn",
        "noDangerouslySetInnerHtml": "warn"
      },
      "style": {
        "useSelfClosingElements": "warn",
        "noCommaOperator": "warn",
        "noInferrableTypes": "warn",
        "useConst": "warn",
        "useShorthandFunctionType": "warn",
        "noArguments": "warn",
        "useDefaultParameterLast": "warn",
        "noUnusedTemplateLiteral": "warn",
        "useExponentiationOperator": "warn",
        "useEnumInitializers": "warn",
        "useAsConstAssertion": "warn",
        "useNodejsImportProtocol": "warn",
        "useNumberNamespace": "warn",
        "noNonNullAssertion": "warn",
        "useWhile": "warn",
        "useLiteralEnumMembers": "warn",
        "noUselessElse": "warn",
        "useSingleVarDeclarator": "warn",
        "noParameterAssign": "warn",
        "useNumericLiterals": "warn",
        "useExportType": "warn",
        "useImportType": "warn",
        "noVar": "warn",
        "useTemplate": "warn"
      },
      "suspicious": {
        "noAsyncPromiseExecutor": "warn",
        "noLabelVar": "warn",
        "noDuplicateObjectKeys": "warn",
        "noUnsafeDeclarationMerging": "warn",
        "noDoubleEquals": "warn",
        "noDuplicateParameters": "warn",
        "noFocusedTests": "warn",
        "noFunctionAssign": "warn",
        "noGlobalIsNan": "warn",
        "noConfusingVoidType": "warn",
        "useDefaultSwitchClauseLast": "warn",
        "useIsArray": "warn",
        "noImplicitAnyLet": "warn",
        "noEmptyInterface": "warn",
        "noExplicitAny": "warn",
        "noAssignInExpressions": "warn",
        "useGetterReturn": "warn",
        "useValidTypeof": "warn",
        "useNamespaceKeyword": "warn",
        "noControlCharactersInRegex": "warn",
        "noMisleadingCharacterClass": "warn",
        "noImportAssign": "warn",
        "noExtraNonNullAssertion": "warn",
        "noCommentText": "warn",
        "noFallthroughSwitchClause": "warn",
        "noShadowRestrictedNames": "warn",
        "noArrayIndexKey": "warn",
        "noRedeclare": "warn",
        "noConfusingLabels": "warn",
        "noCompareNegZero": "warn",
        "noConstEnum": "warn",
        "noMisrefactoredShorthandAssign": "warn",
        "noCatchAssign": "warn",
        "noSelfCompare": "warn",
        "noGlobalAssign": "warn",
        "noPrototypeBuiltins": "warn",
        "noClassAssign": "warn",
        "noDuplicateCase": "warn",
        "noApproximativeNumericConstant": "warn",
        "noDebugger": "warn",
        "noGlobalIsFinite": "warn",
        "noDuplicateTestHooks": "warn",
        "noMisleadingInstantiator": "warn",
        "noRedundantUseStrict": "warn",
        "noThenProperty": "warn",
        "noDuplicateClassMembers": "warn",
        "noSuspiciousSemicolonInJsx": "warn",
        "noUnsafeNegation": "warn",
        "noSparseArray": "warn",
        "noDuplicateJsxProps": "warn",
        "noExportsInTest": "warn"
      }
    }
  }
}

Complete but broken version

This one is generated based on the ones already there on biomejs website. However, the server would complain that the json is misconfigured - some unknown keywords 🤷‍♀️

{
  "$schema": "https://biomejs.dev/schemas/1.8.3/schema.json",
  "formatter": { "enabled": false },
  "organizeImports": { "enabled": true },
  "linter": {
    "enabled": true,
    "rules": {
      "accessibility": {
        "useMediaCaption": "warn",
        "noAutofocus": "warn",
        "noRedundantAlt": "warn",
        "noLabelWithoutControl": "warn",
        "useHtmlLang": "warn",
        "useAriaActivedescendantWithTabindex": "warn",
        "noAriaHiddenOnFocusable": "warn",
        "useIframeTitle": "warn",
        "noAccessKey": "warn",
        "noDistractingElements": "warn",
        "noRedundantRoles": "warn",
        "noNoninteractiveElementToInteractiveRole": "warn",
        "useAriaPropsForRole": "warn",
        "useGenericFontNames": "warn",
        "useFocusableInteractive": "warn",
        "noBlankTarget": "warn",
        "useValidAnchor": "warn",
        "noHeaderScope": "warn",
        "useValidLang": "warn",
        "useKeyWithMouseEvents": "warn",
        "noNoninteractiveTabindex": "warn",
        "useAltText": "warn",
        "noSvgWithoutTitle": "warn",
        "useHeadingContent": "warn",
        "noPositiveTabindex": "warn",
        "useAnchorContent": "warn",
        "useValidAriaRole": "warn",
        "useValidAriaValues": "warn",
        "useSemanticElements": "warn",
        "useButtonType": "warn",
        "useValidAriaProps": "warn",
        "useKeyWithClickEvents": "warn",
        "noAriaUnsupportedElements": "warn",
        "noInteractiveElementToNoninteractiveRole": "warn"
      },
      "complexity": {
        "noUselessSwitchCase": "warn",
        "noUselessFragments": "warn",
        "noThisInStatic": "warn",
        "noUselessUndefinedInitialization": "warn",
        "useSimpleNumberKeys": "warn",
        "noUselessCatch": "warn",
        "noEmptyTypeParameters": "warn",
        "noUselessThisAlias": "warn",
        "noVoid": "warn",
        "noUselessConstructor": "warn",
        "noUselessLoneBlockStatements": "warn",
        "useFlatMap": "warn",
        "noExcessiveCognitiveComplexity": "warn",
        "useRegexLiterals": "warn",
        "useDateNow": "warn",
        "noStaticOnlyClass": "warn",
        "useOptionalChain": "warn",
        "noUselessEmptyExport": "warn",
        "noExtraBooleanCast": "warn",
        "noUselessTypeConstraint": "warn",
        "noForEach": "warn",
        "noBannedTypes": "warn",
        "noMultipleSpacesInRegularExpressionLiterals": "warn",
        "noWith": "warn",
        "useLiteralKeys": "warn",
        "noUselessTernary": "warn",
        "noUselessRename": "warn",
        "noUselessStringConcat": "warn",
        "useSimplifiedLogicExpression": "warn",
        "useArrowFunction": "warn",
        "noExcessiveNestedTestSuites": "warn",
        "noUselessLabel": "warn"
      },
      "correctness": {
        "noUnreachable": "warn",
        "noInvalidBuiltinInstantiation": "warn",
        "noUnknownMediaFeatureName": "warn",
        "noNodejsModules": "warn",
        "noUnknownUnit": "warn",
        "noSetterReturn": "warn",
        "useImportExtensions": "warn",
        "noInvalidPositionAtImportRule": "warn",
        "useYield": "warn",
        "noSwitchDeclarations": "warn",
        "noUnknownFunction": "warn",
        "noUnusedLabels": "warn",
        "noUnusedPrivateClassMembers": "warn",
        "noUnsafeFinally": "warn",
        "noChildrenProp": "warn",
        "noInvalidNewBuiltin": "warn",
        "useIsNan": "warn",
        "noEmptyPattern": "warn",
        "noInvalidConstructorSuper": "warn",
        "noInvalidDirectionInLinearGradient": "warn",
        "noRenderReturnValue": "warn",
        "noUnknownProperty": "warn",
        "noUnusedFunctionParameters": "warn",
        "noInvalidGridAreas": "warn",
        "noSelfAssign": "warn",
        "useArrayLiterals": "warn",
        "noConstAssign": "warn",
        "noFlatMapIdentity": "warn",
        "noStringCaseMismatch": "warn",
        "noUnusedImports": "warn",
        "noUndeclaredVariables": "warn",
        "noPrecisionLoss": "warn",
        "noGlobalObjectCalls": "warn",
        "noUnreachableSuper": "warn",
        "noConstructorReturn": "warn",
        "noNonoctalDecimalEscape": "warn",
        "useJsxKeyInIterable": "warn",
        "noEmptyCharacterClassInRegex": "warn",
        "noInnerDeclarations": "warn",
        "noConstantCondition": "warn",
        "noVoidElementsWithChildren": "warn",
        "noUnsafeOptionalChaining": "warn",
        "useExhaustiveDependencies": "warn",
        "useValidForDirection": "warn",
        "noUndeclaredDependencies": "warn",
        "noInvalidUseBeforeDeclaration": "warn",
        "noUnnecessaryContinue": "warn",
        "useHookAtTopLevel": "warn",
        "noVoidTypeReturn": "warn",
        "noUnmatchableAnbSelector": "warn",
        "noUnusedVariables": "warn",
        "noNewSymbol": "warn",
        "noConstantMathMinMaxClamp": "warn"
      },
      "nursery": {
        "useValidAutocomplete": "warn",
        "useAdjacentOverloadSignatures": "warn",
        "useDeprecatedReason": "warn",
        "noUnknownPseudoClass": "warn",
        "useStrictMode": "warn",
        "noUselessEscapeInRegex": "warn",
        "useConsistentCurlyBraces": "warn",
        "noDuplicatedFields": "warn",
        "noUnknownPseudoElement": "warn",
        "noExportedImports": "warn",
        "useSortedClasses": "warn",
        "noIrregularWhitespace": "warn",
        "noValueAtRule": "warn",
        "noRestrictedImports": "warn",
        "noProcessEnv": "warn",
        "noSecrets": "warn",
        "useConsistentMemberAccessibility": "warn",
        "useTrimStartEnd": "warn",
        "noCommonJs": "warn",
        "useAriaPropsSupportedByRole": "warn",
        "noDynamicNamespaceImportAccess": "warn",
        "noDuplicateCustomProperties": "warn",
        "noStaticElementInteractions": "warn",
        "noRestrictedTypes": "warn",
        "noDuplicateElseIf": "warn",
        "noEnum": "warn",
        "useImportRestrictions": "warn",
        "noSubstr": "warn"
      },
      "performance": {
        "noBarrelFile": "warn",
        "useTopLevelRegex": "warn",
        "noDelete": "warn",
        "noAccumulatingSpread": "warn",
        "noReExportAll": "warn"
      },
      "security": {
        "noDangerouslySetInnerHtmlWithChildren": "warn",
        "noGlobalEval": "warn",
        "noDangerouslySetInnerHtml": "warn"
      },
      "style": {
        "useSelfClosingElements": "warn",
        "noRestrictedGlobals": "warn",
        "useConsistentBuiltinInstantiation": "warn",
        "noCommaOperator": "warn",
        "noInferrableTypes": "warn",
        "noNamespaceImport": "warn",
        "useExplicitLengthCheck": "warn",
        "useFilenamingConvention": "warn",
        "useConst": "warn",
        "useShorthandFunctionType": "warn",
        "noArguments": "warn",
        "useDefaultParameterLast": "warn",
        "useFragmentSyntax": "warn",
        "noUnusedTemplateLiteral": "warn",
        "useExponentiationOperator": "warn",
        "useEnumInitializers": "warn",
        "useAsConstAssertion": "warn",
        "useNamingConvention": "warn",
        "noDoneCallback": "warn",
        "useNodejsImportProtocol": "warn",
        "useThrowNewError": "warn",
        "noNamespace": "warn",
        "noShoutyConstants": "warn",
        "useNumberNamespace": "warn",
        "noNonNullAssertion": "warn",
        "useForOf": "warn",
        "useBlockStatements": "warn",
        "noYodaExpression": "warn",
        "useCollapsedElseIf": "warn",
        "useDefaultSwitchClause": "warn",
        "useShorthandAssign": "warn",
        "useWhile": "warn",
        "useLiteralEnumMembers": "warn",
        "useShorthandArrayType": "warn",
        "noUselessElse": "warn",
        "noImplicitBoolean": "warn",
        "useNodeAssertStrict": "warn",
        "useThrowOnlyError": "warn",
        "useSingleVarDeclarator": "warn",
        "useSingleCaseStatement": "warn",
        "noParameterAssign": "warn",
        "noParameterProperties": "warn",
        "useNumericLiterals": "warn",
        "useExportType": "warn",
        "useImportType": "warn",
        "noVar": "warn",
        "useConsistentArrayType": "warn",
        "useTemplate": "warn",
        "noNegationElse": "warn",
        "noDefaultExport": "warn"
      },
      "suspicious": {
        "noAsyncPromiseExecutor": "warn",
        "noLabelVar": "warn",
        "noDuplicateAtImportRules": "warn",
        "noDuplicateObjectKeys": "warn",
        "noUnsafeDeclarationMerging": "warn",
        "noConsole": "warn",
        "noDoubleEquals": "warn",
        "noDuplicateParameters": "warn",
        "noFocusedTests": "warn",
        "noFunctionAssign": "warn",
        "noGlobalIsNan": "warn",
        "noSkippedTests": "warn",
        "noConfusingVoidType": "warn",
        "useAwait": "warn",
        "useDefaultSwitchClauseLast": "warn",
        "useIsArray": "warn",
        "noDuplicateSelectorsKeyframeBlock": "warn",
        "noConsoleLog": "warn",
        "noImplicitAnyLet": "warn",
        "noEmptyInterface": "warn",
        "noExplicitAny": "warn",
        "noAssignInExpressions": "warn",
        "noMisplacedAssertion": "warn",
        "useGetterReturn": "warn",
        "useValidTypeof": "warn",
        "useNamespaceKeyword": "warn",
        "useErrorMessage": "warn",
        "noControlCharactersInRegex": "warn",
        "noMisleadingCharacterClass": "warn",
        "useNumberToFixedDigitsArgument": "warn",
        "noImportAssign": "warn",
        "noExtraNonNullAssertion": "warn",
        "noImportantInKeyframe": "warn",
        "noCommentText": "warn",
        "noFallthroughSwitchClause": "warn",
        "noShadowRestrictedNames": "warn",
        "noArrayIndexKey": "warn",
        "noRedeclare": "warn",
        "noConfusingLabels": "warn",
        "noCompareNegZero": "warn",
        "noConstEnum": "warn",
        "noMisrefactoredShorthandAssign": "warn",
        "noCatchAssign": "warn",
        "noSelfCompare": "warn",
        "noEmptyBlockStatements": "warn",
        "noGlobalAssign": "warn",
        "noPrototypeBuiltins": "warn",
        "noClassAssign": "warn",
        "noDuplicateCase": "warn",
        "noApproximativeNumericConstant": "warn",
        "noDebugger": "warn",
        "noGlobalIsFinite": "warn",
        "noDuplicateTestHooks": "warn",
        "noMisleadingInstantiator": "warn",
        "noEvolvingTypes": "warn",
        "noRedundantUseStrict": "warn",
        "noThenProperty": "warn",
        "noDuplicateClassMembers": "warn",
        "noEmptyBlock": "warn",
        "noReactSpecificProps": "warn",
        "noSuspiciousSemicolonInJsx": "warn",
        "noUnsafeNegation": "warn",
        "noDuplicateFontNames": "warn",
        "noSparseArray": "warn",
        "noDuplicateJsxProps": "warn",
        "noExportsInTest": "warn",
        "noShorthandPropertyOverrides": "warn"
      }
    }
  }
}

How?

Use the following python code to generate the list yourselves - it needs beautiful soup 4 as a dependency:

from bs4 import BeautifulSoup
import requests as rq
request = rq.get("https://biomejs.dev/linter/rules/")
page = BeautifulSoup(request.content)
def rules_set(name: str):
    rules = page.find(id=name).parent.find_next_sibling("table")
    return set([item.text for item in rules.find_all("td")][::3])

rule_groups = ["accessibility", "complexity", "correctness", "nursery", "performance", "security", "style", "suspicious"]
recommended_rules = page.find(id="recommended-rules").parent.find_next_sibling("ul")
recommended_rules_set = set(item.text for item in recommended_rules)
recommended_rules_dict = {r: {s: "warn" for s in rules_set(r) if s in recommended_rules_set} for r in rule_groups}

# Only recommended rules
import json
print(json.dumps(recommended_rules_dict, indent=2))

## If you want to see all the rules
everything = {r: {s: "warn" for s in rules_set(r)} for r in rule_groups}
print(json.dumps(everything, indent=2))