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/
callableTypesRule.ts
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/
callableTypesRule.ts
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/**
* @license
* Copyright 2013 Palantir Technologies, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
import {
getChildOfKind,
isCallSignatureDeclaration,
isConstructSignatureDeclaration,
isIdentifier,
isInterfaceDeclaration,
isTypeLiteralNode,
} from "tsutils";
import * as ts from "typescript";
import * as Lint from "../index";
export class Rule extends Lint.Rules.AbstractRule {
/* tslint:disable:object-literal-sort-keys */
public static metadata: Lint.IRuleMetadata = {
ruleName: "callable-types",
description:
"An interface or literal type with just a call signature can be written as a function type.",
rationale: "style",
optionsDescription: "Not configurable.",
options: null,
type: "style",
typescriptOnly: true,
hasFix: true,
};
/* tslint:enable:object-literal-sort-keys */
public static FAILURE_STRING_FACTORY(type: string, sigSuggestion: string) {
return `${type} has only a call signature — use \`${sigSuggestion}\` instead.`;
}
public apply(sourceFile: ts.SourceFile): Lint.RuleFailure[] {
return this.applyWithFunction(sourceFile, walk);
}
}
function walk(ctx: Lint.WalkContext<void>) {
return ts.forEachChild(ctx.sourceFile, function cb(node: ts.Node): void {
if (
((isInterfaceDeclaration(node) && noSupertype(node)) || isTypeLiteralNode(node)) &&
node.members.length === 1
) {
const member = node.members[0];
if (
(isConstructSignatureDeclaration(member) || isCallSignatureDeclaration(member)) &&
// avoid bad parse
member.type !== undefined
) {
const suggestion = renderSuggestion(member, node, ctx.sourceFile);
const fixStart =
node.kind === ts.SyntaxKind.TypeLiteral
? node.getStart(ctx.sourceFile)
: getChildOfKind(node, ts.SyntaxKind.InterfaceKeyword)!.getStart(
ctx.sourceFile,
);
ctx.addFailureAtNode(
member,
Rule.FAILURE_STRING_FACTORY(
node.kind === ts.SyntaxKind.TypeLiteral ? "Type literal" : "Interface",
suggestion,
),
Lint.Replacement.replaceFromTo(fixStart, node.end, suggestion),
);
}
}
return ts.forEachChild(node, cb);
});
}
/** True if there is no supertype or if the supertype is `Function`. */
function noSupertype(node: ts.InterfaceDeclaration): boolean {
if (node.heritageClauses === undefined) {
return true;
}
if (node.heritageClauses.length !== 1) {
return false;
}
const expr = node.heritageClauses[0].types[0].expression;
return isIdentifier(expr) && expr.text === "Function";
}
function renderSuggestion(
call: ts.CallSignatureDeclaration | ts.ConstructSignatureDeclaration,
parent: ts.InterfaceDeclaration | ts.TypeLiteralNode,
sourceFile: ts.SourceFile,
): string {
const start = call.getStart(sourceFile);
const colonPos = call.type!.pos - 1 - start;
const text = sourceFile.text.substring(start, call.end);
let suggestion = `${text.substr(0, colonPos)} =>${text.substr(colonPos + 1)}`;
if (shouldWrapSuggestion(parent.parent)) {
suggestion = `(${suggestion})`;
}
if (parent.kind === ts.SyntaxKind.InterfaceDeclaration) {
if (parent.typeParameters !== undefined) {
return `type${sourceFile.text.substring(
parent.name.pos,
parent.typeParameters.end + 1,
)} = ${suggestion}`;
} else {
return `type ${parent.name.text} = ${suggestion}`;
}
}
return suggestion.endsWith(";") ? suggestion.slice(0, -1) : suggestion;
}
function shouldWrapSuggestion(parent: ts.Node) {
switch (parent.kind) {
case ts.SyntaxKind.UnionType:
case ts.SyntaxKind.IntersectionType:
case ts.SyntaxKind.ArrayType:
return true;
default:
return false;
}
}