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Merge pull request #32 from buildo/prefer-bimap
Add prefer-bimap
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‎README.md

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Original file line numberDiff line numberDiff line change
@@ -40,14 +40,16 @@ and enable the rules you want, for example
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'fp-ts/lib' (autofixable 🔧)
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- [fp-ts/no-pipeable](docs/rules/no-pipeable.md): Disallow imports from the
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'pipeable' module (autofixable 🔧)
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- [fp-ts/prefer-traverse](docs/rules/prefer-traverse.md): Replace map + sequence
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with traverse (autofixable 🔧)
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- [fp-ts/no-module-imports](docs/rules/no-module-imports.md): Disallow imports
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from fp-ts modules (autofixable 🔧)
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- [fp-ts/no-redundant-flow](docs/rules/no-redundant-flow.md): Remove redundant
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uses of flow (autofixable 🔧)
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- [fp-ts/prefer-traverse](docs/rules/prefer-traverse.md): Replace map + sequence
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with traverse (autofixable 🔧)
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- [fp-ts/prefer-chain](docs/rules/prefer-chain.md): Replace map + flatten with
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chain (autofixable 🔧)
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- [fp-ts/no-module-imports](docs/rules/no-module-imports.md): Disallow imports
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from fp-ts modules (autofixable 🔧)
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- [fp-ts/prefer-bimap](docs/rules/prefer-bimap.md): Replace map + mapLeft with
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bimap (autofixable 🔧)
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## Configurations
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‎docs/rules/prefer-bimap.md

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@@ -0,0 +1,48 @@
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# Replace map + mapLeft with bimap (fp-ts/prefer-chain)
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Suggest replacing the combination of `map` followed by `mapLeft` (or vice-versa)
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with `bimap`.
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**Fixable**: This rule is automatically fixable using the `--fix` flag on the
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command line.
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## Rule Details
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Examples of **incorrect** code for this rule:
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```ts
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import { pipe } from "fp-ts/function";
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import { either } from "fp-ts";
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pipe(
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getResult(),
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either.map((a) => a + 1),
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either.mapLeft((e) => e + 1)
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);
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```
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```ts
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import { pipe } from "fp-ts/function";
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import { either } from "fp-ts";
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pipe(
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getResult(),
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either.mapLeft((e) => e + 1),
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either.map((a) => a + 1)
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);
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```
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Example of **correct** code for this rule:
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```ts
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import { pipe } from "fp-ts/function";
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import { either } from "fp-ts";
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pipe(
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getResult(),
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either.bimap(
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(e) => e + 1,
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(a) => a + 1
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)
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);
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```

‎src/index.ts

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@@ -11,6 +11,7 @@ const suggestions = {
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"prefer-traverse": require("./rules/prefer-traverse").default,
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"no-redundant-flow": require("./rules/no-redundant-flow").default,
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"prefer-chain": require("./rules/prefer-chain").default,
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"prefer-bimap": require("./rules/prefer-bimap").default,
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};
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export const rules = {

‎src/rules/prefer-bimap.ts

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import {
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AST_NODE_TYPES,
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TSESTree,
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} from "@typescript-eslint/experimental-utils";
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import { boolean, option, apply } from "fp-ts";
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import { constVoid, pipe } from "fp-ts/function";
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import {
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calleeIdentifier,
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contextUtils,
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createRule,
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getAdjacentCombinators,
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inferIndent,
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prettyPrint,
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} from "../utils";
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export default createRule({
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name: "prefer-bimap",
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meta: {
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type: "suggestion",
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fixable: "code",
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schema: [],
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docs: {
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category: "Best Practices",
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description: "Replace map + mapLeft with bimap",
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recommended: "warn",
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},
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messages: {
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mapMapLeftIsBimap:
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"{{firstNode}} followed by {{secondNode}} can be replaced by bimap",
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replaceMapMapLeftBimap:
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"replace {{firstNode}} and {{secondNode}} with bimap",
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},
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},
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defaultOptions: [],
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create(context) {
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const { isPipeOrFlowExpression } = contextUtils(context);
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return {
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CallExpression(node) {
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const mapThenMapLeft = () =>
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getAdjacentCombinators<
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TSESTree.CallExpression,
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TSESTree.CallExpression
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>(
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node,
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{
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name: "map",
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types: [AST_NODE_TYPES.CallExpression],
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},
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{
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name: "mapLeft",
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types: [AST_NODE_TYPES.CallExpression],
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},
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true
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);
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const mapLeftThenMap = () =>
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getAdjacentCombinators<
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TSESTree.CallExpression,
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TSESTree.CallExpression
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>(
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node,
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{
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name: "mapLeft",
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types: [AST_NODE_TYPES.CallExpression],
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},
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{
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name: "map",
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types: [AST_NODE_TYPES.CallExpression],
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},
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true
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);
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pipe(
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node,
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isPipeOrFlowExpression,
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boolean.fold(constVoid, () =>
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pipe(
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mapThenMapLeft(),
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option.alt(mapLeftThenMap),
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option.bindTo("combinators"),
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option.bind("calleeIdentifiers", ({ combinators }) =>
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apply.sequenceT(option.option)(
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calleeIdentifier(combinators[0]),
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calleeIdentifier(combinators[1])
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)
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),
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option.map(({ combinators, calleeIdentifiers }) => {
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context.report({
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loc: {
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start: combinators[0].loc.start,
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end: combinators[1].loc.end,
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},
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messageId: "mapMapLeftIsBimap",
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data: {
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firstNode: calleeIdentifiers[0].name,
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secondNode: calleeIdentifiers[1].name,
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},
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suggest: [
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{
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messageId: "replaceMapMapLeftBimap",
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data: {
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firstNode: calleeIdentifiers[0].name,
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secondNode: calleeIdentifiers[1].name,
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},
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fix(fixer) {
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const mapFirst = calleeIdentifiers[0].name === "map";
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const mapNode = mapFirst
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? combinators[0]
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: combinators[1];
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const mapLeftNode = mapFirst
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? combinators[1]
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: combinators[0];
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return [
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fixer.replaceTextRange(
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[combinators[0].range[0], combinators[1].range[1]],
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`${prettyPrint(mapNode.callee).replace(
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/map$/,
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"bimap"
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)}(\n${inferIndent(mapNode)} ${prettyPrint(
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mapLeftNode.arguments[0]!
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)},\n${inferIndent(mapNode)} ${prettyPrint(
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mapNode.arguments[0]!
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)}\n${inferIndent(mapNode)})`
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),
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];
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},
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},
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],
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});
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})
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)
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)
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);
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},
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};
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},
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});

‎src/utils.ts

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@@ -156,6 +156,10 @@ export function prettyPrint(node: TSESTree.Node): string {
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return generate(node as any);
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}
158158

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export function inferIndent(node: TSESTree.Node): string {
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return new Array(node.loc.start.column + 1).join(" ");
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}
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export const contextUtils = <
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TMessageIds extends string,
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TOptions extends readonly unknown[]

‎tests/rules/prefer-bimap.test.ts

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import rule from "../../src/rules/prefer-bimap";
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import { ESLintUtils } from "@typescript-eslint/experimental-utils";
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import { stripIndent } from "common-tags";
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const ruleTester = new ESLintUtils.RuleTester({
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parser: "@typescript-eslint/parser",
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});
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ruleTester.run("prefer-bimap", rule, {
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valid: [
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{
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code: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.bimap(e => e.toString(), a => a.toString())
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)
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`,
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},
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],
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invalid: [
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{
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code: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.map(
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a => a.toString()
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),
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either.mapLeft(
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e => e.toString()
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)
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)
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`,
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errors: [
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{
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messageId: "mapMapLeftIsBimap",
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suggestions: [
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{
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messageId: "replaceMapMapLeftBimap",
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output: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.bimap(
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e => e.toString(),
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a => a.toString()
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)
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)
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`,
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},
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],
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},
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],
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},
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{
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code: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.mapLeft(
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e => e.toString()
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),
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either.map(
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a => a.toString()
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)
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)
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`,
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errors: [
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{
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messageId: "mapMapLeftIsBimap",
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suggestions: [
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{
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messageId: "replaceMapMapLeftBimap",
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output: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.bimap(
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e => e.toString(),
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a => a.toString()
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)
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)
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`,
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},
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],
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},
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],
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},
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{
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code: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.mapLeft(e => e.toString()),
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either.map(a => a.toString())
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)
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`,
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errors: [
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{
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messageId: "mapMapLeftIsBimap",
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suggestions: [
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{
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messageId: "replaceMapMapLeftBimap",
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output: stripIndent`
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import { either } from "fp-ts"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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either.bimap(
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e => e.toString(),
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a => a.toString()
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)
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)
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`,
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},
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],
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},
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],
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},
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{
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code: stripIndent`
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import { mapLeft, map } from "fp-ts/Either"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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mapLeft(e => e.toString()),
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map(a => a.toString())
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)
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`,
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errors: [
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{
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messageId: "mapMapLeftIsBimap",
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suggestions: [
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{
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messageId: "replaceMapMapLeftBimap",
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output: stripIndent`
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import { mapLeft, map } from "fp-ts/Either"
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import { pipe } from "fp-ts/function"
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pipe(
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getResult(),
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bimap(
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e => e.toString(),
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a => a.toString()
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)
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)
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`,
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},
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],
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},
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],
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},
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],
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});

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