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fix(eslint-plugin): [prefer-function-type] handle this type #1783

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fix(eslint-plugin): [prefer-function-type] handle this type #1783

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8207dca
fix: no check for this return type (fix #1756)
anikethsaha Mar 23, 2020
409b7df
Merge remote-tracking branch 'upstream/master' into fixes-1756
anikethsaha Mar 24, 2020
364ed4e
chore: fixed the fixer for this (refs #1783)
anikethsaha Mar 24, 2020
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63 changes: 60 additions & 3 deletions packages/eslint-plugin/src/rules/prefer-function-type.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,13 @@ import {
} from '@typescript-eslint/experimental-utils';
import * as util from '../util';

const possibleReturnThisTypeHolders = new Set([
AST_NODE_TYPES.TSTypeReference,
AST_NODE_TYPES.TSThisType,
AST_NODE_TYPES.TSFunctionType,
AST_NODE_TYPES.TSTypeAnnotation,
]);

export default util.createRule({
name: 'prefer-function-type',
meta: {
Expand All @@ -26,6 +33,35 @@ export default util.createRule({
create(context) {
const sourceCode = context.getSourceCode();

/**
* Get the range of the `this` which is being used as a type annotation else returns null
* @param node The node being checked
* @returns {Array<number> | null} the range or null if no `this` type annotation are found
*/
function getReturnType(
node: TSESTree.TSTypeAnnotation,
): Array<number> | null {
if (!possibleReturnThisTypeHolders.has(node.type)) {
return null;
}

if (node.type === AST_NODE_TYPES.TSThisType) {
return node.range;
}
Comment on lines +48 to +50
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There are few overlapping issue while comparing which is why I think the CI is failing, should I turn off the rule there ?

This is failing the typecheck because it can never be true.
Your argument is of type TSESTree.TypeAnnotation, which is a container node.

See my other comment for a suggestion of how to structure the function.


if (node.type === AST_NODE_TYPES.TSTypeAnnotation) {
if (node.typeAnnotation.type === AST_NODE_TYPES.TSThisType) {
return node.typeAnnotation.range;
}
}

if (node.type === AST_NODE_TYPES.TSFunctionType) {
return getReturnType(node?.returnType);
}

return null;
}
Comment on lines +41 to +63
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Suggested change
function getReturnType(
node: TSESTree.TSTypeAnnotation,
): Array<number> | null {
if (!possibleReturnThisTypeHolders.has(node.type)) {
return null;
}
if (node.type === AST_NODE_TYPES.TSThisType) {
return node.range;
}
if (node.type === AST_NODE_TYPES.TSTypeAnnotation) {
if (node.typeAnnotation.type === AST_NODE_TYPES.TSThisType) {
return node.typeAnnotation.range;
}
}
if (node.type === AST_NODE_TYPES.TSFunctionType) {
return getReturnType(node?.returnType);
}
return null;
}
function getReturnType(
node: TSESTree.TSTypeAnnotation,
): Array<number> | null {
if (node.typeAnnotation.type === AST_NODE_TYPES.TSThisType) {
return node.range;
}
if (node.typeAnnotation.type === AST_NODE_TYPES.TSFunctionType) {
return getReturnType(node?.returnType);
}
// etc
return null;
}

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I tried this

    function getReturnType(
      node: TSESTree.TSTypeAnnotation,
    ): Array<number> | null {
      if (!possibleReturnThisTypeHolders.has(node.type)) {
        return null;
      }

      if (node.typeAnnotation.type === AST_NODE_TYPES.TSThisType) {
        return node.range;
      }

      if (node.typeAnnotation.type === AST_NODE_TYPES.TSTypeAnnotation) { // <--- type error
        if (node.typeAnnotation.type === AST_NODE_TYPES.TSThisType) {  // <--- type error
          return node.typeAnnotation.range;
        }
      }

      if (node.typeAnnotation.type === AST_NODE_TYPES.TSFunctionType) {
        return getReturnType(node?.returnType);
      }

      return null;
    }

Still no luck, even tests are failing cause of this !


/**
* Checks if there the interface has exactly one supertype that isn't named 'Function'
* @param node The node being checked
Expand Down Expand Up @@ -76,11 +112,32 @@ export default util.createRule({
const start = call.range[0];
const colonPos = call.returnType!.range[0] - start;
const text = sourceCode.getText().slice(start, call.range[1]);
const returnType = getReturnType(call.returnType?.typeAnnotation);
let lhs = text.slice(0, colonPos);
let rhs = text.slice(colonPos + 1);

let suggestion = `${text.slice(0, colonPos)} =>${text.slice(
colonPos + 1,
)}`;
if (returnType !== null && returnType.length === 2) {
if (
sourceCode.getText().slice(returnType[0], returnType[1]) === 'this'
) {
// safe to change
rhs = rhs.replace('this', parent.id.name);
}
}

if (call.params.length > 0) {
call.params.forEach(param => {
if (
param.typeAnnotation?.typeAnnotation?.type ===
AST_NODE_TYPES.TSThisType
) {
// replacing each first occurance of `this`
lhs = lhs.replace('this', parent.id.name);
}
});
}

let suggestion = `${lhs} =>${rhs}`;
if (shouldWrapSuggestion(parent.parent)) {
suggestion = `(${suggestion})`;
}
Expand Down
61 changes: 61 additions & 0 deletions packages/eslint-plugin/tests/rules/prefer-function-type.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,7 @@ interface Foo {
interface Bar extends Function, Foo {
(): void;
}`,
'interface Interface {(arg: this): this, [key : number] : string}',
],

invalid: [
Expand Down Expand Up @@ -129,5 +130,65 @@ interface Foo<T> {
output: `
type Foo<T> = (bar: T) => string;`,
},
{
code: 'interface Foo { (): () => this; }',
errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Foo = () => () => Foo;`,
},
{
code: 'interface Foo { (): () => string; }',
errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Foo = () => () => string;`,
},
{
code: 'interface Interface {(): this}',
errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Interface = () => Interface`,
},
{
code: 'interface Interface {(): Object<this>}',
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@bradzacher this ( generic types ) will fail as the latest commit is still WIP.

errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Foo = () => () => this;`,
},
{
code: 'interface Interface {() : string}',
errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Interface = () => string`,
},
{
code: 'interface Interface {(arg: this): this}',
errors: [
{
messageId: 'functionTypeOverCallableType',
tyoe: AST_NODE_TYPES.TSCallSignatureDeclaration,
},
],
output: `type Interface = (arg: Interface) => Interface`,
},
],
});