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feat(spawn-usage): throw error if spawn-usage is used with xstate > 4
Using the rule no longer makes sense in XState v5 since the new API makes it impossible to call it outside of an assign function.
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‎README.md

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@@ -96,7 +96,7 @@ The default shareable configurations are for XState v5. If you use the older XSt
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| Rule | Description | Recommended |
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| ---------------------------------------------------------------------------------- | ------------------------------------------------------------------ | ------------------ |
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| [spawn-usage](docs/rules/spawn-usage.md) | Enforce correct usage of `spawn` | :heavy_check_mark: |
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| [spawn-usage](docs/rules/spawn-usage.md) | Enforce correct usage of `spawn`. **Only for XState v4!** | :heavy_check_mark: |
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| [no-infinite-loop](docs/rules/no-infinite-loop.md) | Detect infinite loops with eventless transitions | :heavy_check_mark: |
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| [no-imperative-action](docs/rules/no-imperative-action.md) | Forbid using action creators imperatively | :heavy_check_mark: |
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| [no-ondone-outside-compound-state](docs/rules/no-ondone-outside-compound-state.md) | Forbid onDone transitions on `atomic`, `history` and `final` nodes | :heavy_check_mark: |

‎docs/rules/spawn-usage.md

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@@ -2,10 +2,16 @@
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Ensure that the `spawn` function imported from xstate is used correctly.
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** This rule is compatible with XState v4 only! **
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## Rule Details
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The `spawn` function has to be used in the context of an assignment function. Failing to do so creates an orphaned actor which has no effect.
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### XState v5
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XState v5 changed the way the `spawn` function is accessed. This effectively eliminated the possibility of using the `spawn` function outside of the `assign` function. Therefore, this rule becomes obsolete in XState v5. Do not use it with XState v5.
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Examples of **incorrect** code for this rule:
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```javascript

‎lib/index.js

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@@ -38,7 +38,6 @@ module.exports = {
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},
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plugins: ['xstate'],
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rules: {
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'xstate/spawn-usage': 'error',
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'xstate/no-infinite-loop': 'error',
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'xstate/no-imperative-action': 'error',
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'xstate/no-ondone-outside-compound-state': 'error',
@@ -62,7 +61,6 @@ module.exports = {
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},
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plugins: ['xstate'],
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rules: {
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'xstate/spawn-usage': 'error',
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'xstate/no-infinite-loop': 'error',
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'xstate/no-imperative-action': 'error',
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'xstate/no-ondone-outside-compound-state': 'error',

‎lib/rules/spawn-usage.js

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@@ -1,8 +1,17 @@
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'use strict'
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/**
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* This rule is relevant only for XState v4.
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*
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*/
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const getDocsUrl = require('../utils/getDocsUrl')
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const { isFunctionExpression, isIIFE } = require('../utils/predicates')
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const XStateDetector = require('../utils/XStateDetector')
10+
const getSettings = require('../utils/getSettings')
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12+
// TODO instead of the detector, consider using:
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// context.getDeclaredVariables(node)
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// context.sourceCode.getScope(node).variables
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function isAssignCall(node) {
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return node.type === 'CallExpression' && node.callee.name === 'assign'
@@ -30,8 +39,6 @@ function isInsideAssignerFunction(node) {
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if (isAssignCall(parent)) {
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return false
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}
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// TODO it's possible that a function expression inside assigner function
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// does not get called, so nothing is ever spawned
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parent = parent.parent
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}
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return false
@@ -55,6 +62,18 @@ module.exports = {
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create: function (context) {
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const xstateDetector = new XStateDetector()
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const { version } = getSettings(context)
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if (version !== 4) {
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throw new Error(`Rule "spawn-usage" should be used with XState v4 only! Your XState version: ${version}. Either remove this rule from your ESLint config or set the correct version of XState in the config:
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{
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"settings": {
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"xstate": {
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"version": 4
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}
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}
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}
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`)
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}
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return {
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...xstateDetector.visitors,

‎tests/lib/rules/spawn-usage.js

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@@ -1,84 +1,120 @@
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const RuleTester = require('eslint').RuleTester
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const rule = require('../../../lib/rules/spawn-usage')
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const { withVersion } = require('../utils/settings')
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const tests = {
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valid: [
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// not imported from xstate - ignore the rule
7-
`
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withVersion(
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4,
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`
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spawn(x)
9-
`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign({
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ref: () => spawn(x)
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign({
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ref: () => spawn(x)
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign({
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ref: () => spawn(x)
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign(() => ({
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ref: spawn(x, 'id')
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}))
33-
`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign(() => {
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return {
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ref: spawn(x)
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}
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign(() => {
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const ref = spawn(x)
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return {
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ref,
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}
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign(() => {
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const start = () => spawn(x)
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return {
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ref: start()
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}
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})
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`,
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`
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),
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withVersion(
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4,
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`
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import { spawn } from 'xstate'
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assign({
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ref: function() { return spawn(x) }
6491
})
65-
`,
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`
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),
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withVersion(
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4,
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`
6797
import { spawn } from 'xstate'
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assign(function() {
6999
return {
70100
ref: spawn(x, 'id')
71101
}
72102
})
73-
`,
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// other import types
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`
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),
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// other import types
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withVersion(
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4,
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`
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import { spawn as foo } from 'xstate'
77110
assign({
78111
ref: () => foo(x)
79112
})
80-
`,
81113
`
114+
),
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withVersion(
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4,
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`
82118
import xs from 'xstate'
83119
const { spawn } = xs
84120
const foo = xs.spawn
@@ -89,8 +125,11 @@ const tests = {
89125
ref3: () => xs.spawn(x),
90126
ref4: () => xs['spawn'](x),
91127
})
92-
`,
93128
`
129+
),
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withVersion(
131+
4,
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`
94133
import * as xs from 'xstate'
95134
const { spawn } = xs
96135
const foo = xs.spawn
@@ -101,50 +140,51 @@ const tests = {
101140
ref3: () => xs.spawn(x),
102141
ref4: () => xs['spawn'](x),
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})
104-
`,
143+
`
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),
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],
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invalid: [
107-
{
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withVersion(4, {
108148
code: `
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import { spawn } from 'xstate'
110150
spawn(x)
111151
`,
112152
errors: [{ messageId: 'invalidCallContext' }],
113-
},
114-
{
153+
}),
154+
withVersion(4, {
115155
code: `
116156
import { spawn } from 'xstate'
117157
assign(spawn(x))
118158
`,
119159
errors: [{ messageId: 'invalidCallContext' }],
120-
},
121-
{
160+
}),
161+
withVersion(4, {
122162
code: `
123163
import { spawn } from 'xstate'
124164
assign({
125165
ref: spawn(x)
126166
})
127167
`,
128168
errors: [{ messageId: 'invalidCallContext' }],
129-
},
130-
{
169+
}),
170+
withVersion(4, {
131171
code: `
132172
import { spawn } from 'xstate'
133173
assign((() => ({
134174
ref: spawn(x)
135175
}))())
136176
`,
137177
errors: [{ messageId: 'invalidCallContext' }],
138-
},
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}),
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// test other import types with a single invalid call
140-
{
180+
withVersion(4, {
141181
code: `
142182
import { spawn as foo } from 'xstate'
143183
foo(x)
144184
`,
145185
errors: [{ messageId: 'invalidCallContext' }],
146-
},
147-
{
186+
}),
187+
withVersion(4, {
148188
code: `
149189
import xs from 'xstate'
150190
const { spawn } = xs
@@ -162,8 +202,8 @@ const tests = {
162202
{ messageId: 'invalidCallContext' },
163203
{ messageId: 'invalidCallContext' },
164204
],
165-
},
166-
{
205+
}),
206+
withVersion(4, {
167207
code: `
168208
import * as xs from 'xstate'
169209
const { spawn } = xs
@@ -181,54 +221,35 @@ const tests = {
181221
{ messageId: 'invalidCallContext' },
182222
{ messageId: 'invalidCallContext' },
183223
],
184-
},
185-
{
224+
}),
225+
withVersion(4, {
186226
code: `
187227
const { spawn } = require('xstate')
188228
spawn(x)
189229
`,
190230
errors: [{ messageId: 'invalidCallContext' }],
191-
},
192-
{
231+
}),
232+
withVersion(4, {
193233
code: `
194234
const spawn = require('xstate').spawn
195235
spawn(x)
196236
`,
197237
errors: [{ messageId: 'invalidCallContext' }],
198-
},
199-
{
238+
}),
239+
withVersion(4, {
200240
code: `
201241
const spawn = require('xstate')['spawn']
202242
spawn(x)
203243
`,
204244
errors: [{ messageId: 'invalidCallContext' }],
205-
},
206-
{
245+
}),
246+
withVersion(4, {
207247
code: `
208248
const xs = require('xstate')
209249
xs.spawn(x)
210250
`,
211251
errors: [{ messageId: 'invalidCallContext' }],
212-
},
213-
// {
214-
// code: `
215-
// import xs from 'xstate'
216-
// xs.spawn(x)
217-
// `,
218-
// errors: [{ messageId: 'invalidCallContext' }],
219-
// },
220-
// TODO extend the rule to catch this use case
221-
// {
222-
// code: `
223-
// assign(() => {
224-
// const start = () => spawn(x)
225-
// return {
226-
// ref: start
227-
// }
228-
// })
229-
// `,
230-
// errors: [{ messageId: 'spawnNeverCalled' }],
231-
// },
252+
}),
232253
],
233254
}
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