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📄 no-unnecessary-type-arguments.ts

📊 Analysis Summary

Metric Count
🔧 Functions 15
📦 Imports 6
📊 Variables & Constants 2
📑 Type Aliases 2

📚 Table of Contents

🛠️ File Location:

📂 packages/eslint-plugin/src/rules/no-unnecessary-type-arguments.ts

📦 Imports

Name Source
TSESTree @typescript-eslint/utils
AST_NODE_TYPES @typescript-eslint/utils
createRule ../util
findFirstResult ../util
getParserServices ../util
isTypeReferenceType ../util

Variables & Constants

Name Type Kind Value Exported
i number const esParameters.params.length - 1 ✗
arg any const esParameters.params[i] ✗

Functions

`getTypeForComparison(type: ts.Type): {

  type: ts.Type;
  typeArguments: readonly ts.Type[];
}`
Code 
function getTypeForComparison(type: ts.Type): {
      type: ts.Type;
      typeArguments: readonly ts.Type[];
    } {
      if (isTypeReferenceType(type)) {
        return {
          type: type.target,
          typeArguments: checker.getTypeArguments(type),
        };
      }
      return {
        type,
        typeArguments: [],
      };
    }
  • Parameters:
  • type: ts.Type
  • Return Type: { type: ts.Type; typeArguments: readonly ts.Type[]; }
  • Calls:
  • isTypeReferenceType (from ../util)
  • checker.getTypeArguments

checkTSArgsAndParameters(esParameters: TSESTree.TSTypeParameterInstantiation, typeParameters: readonly ts.TypeParameterDeclaration[]): void

Code 
function checkTSArgsAndParameters(
      esParameters: TSESTree.TSTypeParameterInstantiation,
      typeParameters: readonly ts.TypeParameterDeclaration[],
    ): void {
      // Just check the last one. Must specify previous type parameters if the last one is specified.
      const i = esParameters.params.length - 1;
      const arg = esParameters.params[i];
      const param = typeParameters.at(i);
      if (!param?.default) {
        return;
      }

      // TODO: would like checker.areTypesEquivalent. https://github.com/Microsoft/TypeScript/issues/13502
      const defaultType = checker.getTypeAtLocation(param.default);
      const argType = services.getTypeAtLocation(arg);
      // this check should handle some of the most simple cases of like strings, numbers, etc
      if (defaultType !== argType) {
        // For more complex types (like aliases to generic object types) - TS won't always create a
        // global shared type object for the type - so we need to resort to manually comparing the
        // reference type and the passed type arguments.
        // Also - in case there are aliases - we need to resolve them before we do checks
        const defaultTypeResolved = getTypeForComparison(defaultType);
        const argTypeResolved = getTypeForComparison(argType);
        if (
          // ensure the resolved type AND all the parameters are the same
          defaultTypeResolved.type !== argTypeResolved.type ||
          defaultTypeResolved.typeArguments.length !==
            argTypeResolved.typeArguments.length ||
          defaultTypeResolved.typeArguments.some(
            (t, i) => t !== argTypeResolved.typeArguments[i],
          )
        ) {
          return;
        }
      }

      context.report({
        node: arg,
        messageId: 'unnecessaryTypeParameter',
        fix: fixer =>
          fixer.removeRange(
            i === 0
              ? esParameters.range
              : [esParameters.params[i - 1].range[1], arg.range[1]],
          ),
      });
    }
  • Parameters:
  • esParameters: TSESTree.TSTypeParameterInstantiation
  • typeParameters: readonly ts.TypeParameterDeclaration[]
  • Return Type: void
  • Calls:
  • typeParameters.at
  • checker.getTypeAtLocation
  • services.getTypeAtLocation
  • getTypeForComparison
  • defaultTypeResolved.typeArguments.some
  • context.report
  • fixer.removeRange
  • Internal Comments: 
    // Just check the last one. Must specify previous type parameters if the last one is specified. (x2)
// TODO: would like checker.areTypesEquivalent. https://github.com/Microsoft/TypeScript/issues/13502 (x2)
// this check should handle some of the most simple cases of like strings, numbers, etc
// For more complex types (like aliases to generic object types) - TS won't always create a (x2)
// global shared type object for the type - so we need to resort to manually comparing the (x2)
// reference type and the passed type arguments. (x2)
// Also - in case there are aliases - we need to resolve them before we do checks (x2)
// ensure the resolved type AND all the parameters are the same (x5)

fix(fixer: any): any

Code 
fixer =>
          fixer.removeRange(
            i === 0
              ? esParameters.range
              : [esParameters.params[i - 1].range[1], arg.range[1]],
          )
  • Parameters:
  • fixer: any
  • Return Type: any
  • Calls:
  • fixer.removeRange

fix(fixer: any): any

Code 
fixer =>
          fixer.removeRange(
            i === 0
              ? esParameters.range
              : [esParameters.params[i - 1].range[1], arg.range[1]],
          )
  • Parameters:
  • fixer: any
  • Return Type: any
  • Calls:
  • fixer.removeRange

fix(fixer: any): any

Code 
fixer =>
          fixer.removeRange(
            i === 0
              ? esParameters.range
              : [esParameters.params[i - 1].range[1], arg.range[1]],
          )
  • Parameters:
  • fixer: any
  • Return Type: any
  • Calls:
  • fixer.removeRange

fix(fixer: any): any

Code 
fixer =>
          fixer.removeRange(
            i === 0
              ? esParameters.range
              : [esParameters.params[i - 1].range[1], arg.range[1]],
          )
  • Parameters:
  • fixer: any
  • Return Type: any
  • Calls:
  • fixer.removeRange

getTypeParametersFromNode(node: TSESTree.TSTypeParameterInstantiation, tsNode: ParameterCapableTSNode, checker: ts.TypeChecker): readonly ts.TypeParameterDeclaration[] | undefined

Code 
function getTypeParametersFromNode(
  node: TSESTree.TSTypeParameterInstantiation,
  tsNode: ParameterCapableTSNode,
  checker: ts.TypeChecker,
): readonly ts.TypeParameterDeclaration[] | undefined {
  if (ts.isExpressionWithTypeArguments(tsNode)) {
    return getTypeParametersFromType(node, tsNode.expression, checker);
  }

  if (ts.isTypeReferenceNode(tsNode)) {
    return getTypeParametersFromType(node, tsNode.typeName, checker);
  }

  if (
    ts.isCallExpression(tsNode) ||
    ts.isNewExpression(tsNode) ||
    ts.isTaggedTemplateExpression(tsNode) ||
    ts.isJsxOpeningElement(tsNode) ||
    ts.isJsxSelfClosingElement(tsNode)
  ) {
    return getTypeParametersFromCall(node, tsNode, checker);
  }

  return undefined;
}
  • Parameters:
  • node: TSESTree.TSTypeParameterInstantiation
  • tsNode: ParameterCapableTSNode
  • checker: ts.TypeChecker
  • Return Type: readonly ts.TypeParameterDeclaration[] | undefined
  • Calls:
  • ts.isExpressionWithTypeArguments
  • getTypeParametersFromType
  • ts.isTypeReferenceNode
  • ts.isCallExpression
  • ts.isNewExpression
  • ts.isTaggedTemplateExpression
  • ts.isJsxOpeningElement
  • ts.isJsxSelfClosingElement
  • getTypeParametersFromCall

getTypeParametersFromType(node: TSESTree.TSTypeParameterInstantiation, type: ts.ClassDeclaration | ts.EntityName | ts.Expression, checker: ts.TypeChecker): readonly ts.TypeParameterDeclaration[] | undefined

Code 
function getTypeParametersFromType(
  node: TSESTree.TSTypeParameterInstantiation,
  type: ts.ClassDeclaration | ts.EntityName | ts.Expression,
  checker: ts.TypeChecker,
): readonly ts.TypeParameterDeclaration[] | undefined {
  const symAtLocation = checker.getSymbolAtLocation(type);
  if (!symAtLocation) {
    return undefined;
  }

  const sym = getAliasedSymbol(symAtLocation, checker);
  const declarations = sym.getDeclarations();

  if (!declarations) {
    return undefined;
  }

  const sortedDeclaraions = sortDeclarationsByTypeValueContext(
    node,
    declarations,
  );
  return findFirstResult(sortedDeclaraions, decl => {
    if (
      ts.isTypeAliasDeclaration(decl) ||
      ts.isInterfaceDeclaration(decl) ||
      ts.isClassLike(decl)
    ) {
      return decl.typeParameters;
    }
    if (ts.isVariableDeclaration(decl)) {
      return getConstructSignatureDeclaration(symAtLocation, checker)
        ?.typeParameters;
    }
    return undefined;
  });
}
  • Parameters:
  • node: TSESTree.TSTypeParameterInstantiation
  • type: ts.ClassDeclaration | ts.EntityName | ts.Expression
  • checker: ts.TypeChecker
  • Return Type: readonly ts.TypeParameterDeclaration[] | undefined
  • Calls:
  • checker.getSymbolAtLocation
  • getAliasedSymbol
  • sym.getDeclarations
  • sortDeclarationsByTypeValueContext
  • findFirstResult (from ../util)
  • ts.isTypeAliasDeclaration
  • ts.isInterfaceDeclaration
  • ts.isClassLike
  • ts.isVariableDeclaration
  • getConstructSignatureDeclaration

`getTypeParametersFromCall(node: TSESTree.TSTypeParameterInstantiation, tsNode: | ts.CallExpression

| ts.JsxOpeningElement
| ts.JsxSelfClosingElement
| ts.NewExpression
| ts.TaggedTemplateExpression, checker: ts.TypeChecker): readonly ts.TypeParameterDeclaration[] | undefined`
Code 
function getTypeParametersFromCall(
  node: TSESTree.TSTypeParameterInstantiation,
  tsNode:
    | ts.CallExpression
    | ts.JsxOpeningElement
    | ts.JsxSelfClosingElement
    | ts.NewExpression
    | ts.TaggedTemplateExpression,
  checker: ts.TypeChecker,
): readonly ts.TypeParameterDeclaration[] | undefined {
  const sig = checker.getResolvedSignature(tsNode);
  const sigDecl = sig?.getDeclaration();
  if (!sigDecl) {
    return ts.isNewExpression(tsNode)
      ? getTypeParametersFromType(node, tsNode.expression, checker)
      : undefined;
  }

  return sigDecl.typeParameters;
}
  • Parameters:
  • node: TSESTree.TSTypeParameterInstantiation
  • tsNode: | ts.CallExpression | ts.JsxOpeningElement | ts.JsxSelfClosingElement | ts.NewExpression | ts.TaggedTemplateExpression
  • checker: ts.TypeChecker
  • Return Type: readonly ts.TypeParameterDeclaration[] | undefined
  • Calls:
  • checker.getResolvedSignature
  • sig?.getDeclaration
  • ts.isNewExpression
  • getTypeParametersFromType

getAliasedSymbol(symbol: ts.Symbol, checker: ts.TypeChecker): ts.Symbol

Code 
function getAliasedSymbol(
  symbol: ts.Symbol,
  checker: ts.TypeChecker,
): ts.Symbol {
  return tsutils.isSymbolFlagSet(symbol, ts.SymbolFlags.Alias)
    ? checker.getAliasedSymbol(symbol)
    : symbol;
}
  • Parameters:
  • symbol: ts.Symbol
  • checker: ts.TypeChecker
  • Return Type: ts.Symbol
  • Calls:
  • tsutils.isSymbolFlagSet
  • checker.getAliasedSymbol

isInTypeContext(node: TSESTree.TSTypeParameterInstantiation): boolean

Code 
function isInTypeContext(node: TSESTree.TSTypeParameterInstantiation) {
  return (
    node.parent.type === AST_NODE_TYPES.TSInterfaceHeritage ||
    node.parent.type === AST_NODE_TYPES.TSTypeReference ||
    node.parent.type === AST_NODE_TYPES.TSClassImplements
  );
}
  • Parameters:
  • node: TSESTree.TSTypeParameterInstantiation
  • Return Type: boolean

isTypeContextDeclaration(decl: ts.Declaration): any

Code 
function isTypeContextDeclaration(decl: ts.Declaration) {
  return ts.isTypeAliasDeclaration(decl) || ts.isInterfaceDeclaration(decl);
}
  • Parameters:
  • decl: ts.Declaration
  • Return Type: any
  • Calls:
  • ts.isTypeAliasDeclaration
  • ts.isInterfaceDeclaration

typeFirstCompare(declA: ts.Declaration, declB: ts.Declaration): number

Code 
function typeFirstCompare(declA: ts.Declaration, declB: ts.Declaration) {
  const aIsType = isTypeContextDeclaration(declA);
  const bIsType = isTypeContextDeclaration(declB);

  return Number(bIsType) - Number(aIsType);
}
  • Parameters:
  • declA: ts.Declaration
  • declB: ts.Declaration
  • Return Type: number
  • Calls:
  • isTypeContextDeclaration
  • Number

sortDeclarationsByTypeValueContext(node: TSESTree.TSTypeParameterInstantiation, declarations: ts.Declaration[]): ts.Declaration[]

Code 
function sortDeclarationsByTypeValueContext(
  node: TSESTree.TSTypeParameterInstantiation,
  declarations: ts.Declaration[],
) {
  const sorted = [...declarations].sort(typeFirstCompare);
  if (isInTypeContext(node)) {
    return sorted;
  }
  return sorted.reverse();
}
  • Parameters:
  • node: TSESTree.TSTypeParameterInstantiation
  • declarations: ts.Declaration[]
  • Return Type: ts.Declaration[]
  • Calls:
  • [...declarations].sort
  • isInTypeContext
  • sorted.reverse

getConstructSignatureDeclaration(symbol: ts.Symbol, checker: ts.TypeChecker): ts.SignatureDeclaration | undefined

Code 
function getConstructSignatureDeclaration(
  symbol: ts.Symbol,
  checker: ts.TypeChecker,
): ts.SignatureDeclaration | undefined {
  const type = checker.getTypeOfSymbol(symbol);
  const sig = type.getConstructSignatures();
  return sig.at(0)?.getDeclaration();
}
  • Parameters:
  • symbol: ts.Symbol
  • checker: ts.TypeChecker
  • Return Type: ts.SignatureDeclaration | undefined
  • Calls:
  • checker.getTypeOfSymbol
  • type.getConstructSignatures
  • sig.at(0)?.getDeclaration

Type Aliases

ParameterCapableTSNode

type ParameterCapableTSNode = | ts.CallExpression
  | ts.ExpressionWithTypeArguments
  | ts.ImportTypeNode
  | ts.JsxOpeningElement
  | ts.JsxSelfClosingElement
  | ts.NewExpression
  | ts.TaggedTemplateExpression
  | ts.TypeQueryNode
  | ts.TypeReferenceNode;

MessageIds

type MessageIds = 'unnecessaryTypeParameter';