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JasonWeinzierlJasonWeinzierl
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feat(no-topromise): suggest an exact replacement for toPromise() (#184)
This adds the "most correct" suggestion to `no-topromise` for replacing `toPromise()`. The old `toPromise()` would resolve to `undefined`, while the new `lastValueFrom` rejects with `EmptyError`. So if a user followed the old top suggestion and replaced `toPromise` with `lastValueFrom`, they might be surprised to find `EmptyError` now thrown instead. This wouldn't be a problem for someone using the `strict` config, which includes `no-ignored-default-value`, but users of the `recommended` config wouldn't get that lint notification. Resolves #168
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‎docs/rules/no-topromise.md‎

Lines changed: 7 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10,9 +10,10 @@
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This rule effects failures if the `toPromise` method is used.
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This rule provides two editor suggestions which replace `toPromise` with either:
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This rule provides three editor suggestions which replace `toPromise` with either:
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15-
- `lastValueFrom(...)`, which behaves closest to the behavior of `toPromise`,
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- `lastValueFrom(..., { defaultValue: undefined })`, which imitates the behavior of `toPromise`,
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- or `lastValueFrom(...)`, which throws `EmptyError` instead of defaulting to `undefined`,
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- or `firstValueFrom(...)`.
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## When Not To Use It
@@ -26,6 +27,10 @@ Type checked lint rules are more powerful than traditional lint rules, but also
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- [Conversion to Promises](https://rxjs.dev/deprecations/to-promise)
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## Related To
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- [`no-ignored-default-value`](./no-ignored-default-value.md)
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## Resources
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- [Rule source](https://github.com/JasonWeinzierl/eslint-plugin-rxjs-x/blob/main/src/rules/no-topromise.ts)

‎src/rules/no-topromise.ts‎

Lines changed: 7 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13,6 +13,7 @@ export const noTopromiseRule = ruleCreator({
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hasSuggestions: true,
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messages: {
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forbidden: 'The toPromise method is forbidden.',
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suggestLastValueFromWithDefault: 'Use lastValueFrom(..., { defaultValue: undefined }) instead.',
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suggestLastValueFrom: 'Use lastValueFrom instead.',
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suggestFirstValueFrom: 'Use firstValueFrom instead.',
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},
@@ -37,6 +38,7 @@ export const noTopromiseRule = ruleCreator({
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callExpression: es.CallExpression,
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observableNode: es.Node,
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importDeclarations: es.ImportDeclaration[],
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{ withDefault }: { withDefault?: boolean } = {},
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) {
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return function* fix(fixer: TSESLint.RuleFixer) {
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let namespace = '';
@@ -74,7 +76,7 @@ export const noTopromiseRule = ruleCreator({
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yield fixer.replaceText(
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callExpression,
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`${namespace}${functionName}(${context.sourceCode.getText(observableNode)})`,
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`${namespace}${functionName}(${context.sourceCode.getText(observableNode)}${withDefault ? ', { defaultValue: undefined }' : ''})`,
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);
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};
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}
@@ -99,6 +101,10 @@ export const noTopromiseRule = ruleCreator({
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messageId: 'forbidden',
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node: memberExpression.property,
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suggest: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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fix: createFix('lastValueFrom', node, memberExpression.object, importDeclarations, { withDefault: true }),
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},
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{
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messageId: 'suggestLastValueFrom',
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fix: createFix('lastValueFrom', node, memberExpression.object, importDeclarations),

‎tests/rules/no-topromise.test.ts‎

Lines changed: 64 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -38,10 +38,19 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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import { of } from "rxjs";
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const a = of("a");
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a.toPromise().then(value => console.log(value));
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~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// observable toPromise
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import { of, lastValueFrom } from "rxjs";
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const a = of("a");
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lastValueFrom(a, { defaultValue: undefined }).then(value => console.log(value));
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`,
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},
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{
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messageId: 'suggestLastValueFrom',
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output: stripIndent`
@@ -69,10 +78,19 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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import { Subject } from "rxjs";
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const a = new Subject<string>();
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a.toPromise().then(value => console.log(value));
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~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// subject toPromise
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import { Subject, lastValueFrom } from "rxjs";
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const a = new Subject<string>();
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lastValueFrom(a, { defaultValue: undefined }).then(value => console.log(value));
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`,
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},
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{
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messageId: 'suggestLastValueFrom',
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output: stripIndent`
@@ -102,11 +120,22 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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a
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.foo$
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.toPromise().then(value => console.log(value))
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~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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.catch(error => console.error(error));
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// weird whitespace
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import { of, lastValueFrom } from "rxjs";
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const a = { foo$: of("a") };
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lastValueFrom(a
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.foo$, { defaultValue: undefined }).then(value => console.log(value))
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.catch(error => console.error(error));
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`,
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},
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{
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messageId: 'suggestLastValueFrom',
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output: stripIndent`
@@ -138,10 +167,19 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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import { lastValueFrom as lvf, of } from "rxjs";
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const a = of("a");
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a.toPromise().then(value => console.log(value));
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~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// lastValueFrom already imported
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import { lastValueFrom as lvf, of } from "rxjs";
179+
const a = of("a");
180+
lvf(a, { defaultValue: undefined }).then(value => console.log(value));
181+
`,
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},
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{
146184
messageId: 'suggestLastValueFrom',
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output: stripIndent`
@@ -170,10 +208,21 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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171209
const a = fromFetch("https://api.some.com");
172210
a.toPromise().then(value => console.log(value));
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~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// rxjs not already imported
219+
import { fromFetch } from "rxjs/fetch";
220+
import { lastValueFrom } from "rxjs";
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222+
const a = fromFetch("https://api.some.com");
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lastValueFrom(a, { defaultValue: undefined }).then(value => console.log(value));
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`,
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},
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{
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messageId: 'suggestLastValueFrom',
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output: stripIndent`
@@ -205,10 +254,19 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
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import * as Rx from "rxjs";
206255
const a = Rx.of("a");
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a.toPromise().then(value => console.log(value));
208-
~~~~~~~~~ [forbidden suggest 0 1]
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~~~~~~~~~ [forbidden suggest 0 1 2]
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`,
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{
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suggestions: [
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{
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messageId: 'suggestLastValueFromWithDefault',
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output: stripIndent`
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// namespace import
265+
import * as Rx from "rxjs";
266+
const a = Rx.of("a");
267+
Rx.lastValueFrom(a, { defaultValue: undefined }).then(value => console.log(value));
268+
`,
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},
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{
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messageId: 'suggestLastValueFrom',
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output: stripIndent`

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