implement

README.md

@@ -320,6 +320,7 @@ These rules relate to possible syntax or logic errors in Svelte code:
 | [svelte/require-store-callbacks-use-set-param](https://sveltejs.github.io/eslint-plugin-svelte/rules/require-store-callbacks-use-set-param/) | store callbacks must use `set` param |  |
 | [svelte/require-store-reactive-access](https://sveltejs.github.io/eslint-plugin-svelte/rules/require-store-reactive-access/) | disallow to use of the store itself as an operand. Need to use $ prefix or get function. | :wrench: |
 | [svelte/valid-compile](https://sveltejs.github.io/eslint-plugin-svelte/rules/valid-compile/) | disallow warnings when compiling. | :star: |
+| [svelte/valid-context-access](https://sveltejs.github.io/eslint-plugin-svelte/rules/valid-context-access/) | context functions must be called during component initialization. |  |
 | [svelte/valid-prop-names-in-kit-pages](https://sveltejs.github.io/eslint-plugin-svelte/rules/valid-prop-names-in-kit-pages/) | disallow props other than data or errors in Svelte Kit page components. |  |
 
 ## Security Vulnerability

docs/rules.md

@@ -33,6 +33,7 @@ These rules relate to possible syntax or logic errors in Svelte code:
 | [svelte/require-store-callbacks-use-set-param](./rules/require-store-callbacks-use-set-param.md)               | store callbacks must use `set` param                                                                                                   |                |
 | [svelte/require-store-reactive-access](./rules/require-store-reactive-access.md)                               | disallow to use of the store itself as an operand. Need to use $ prefix or get function.                                               | :wrench:       |
 | [svelte/valid-compile](./rules/valid-compile.md)                                                               | disallow warnings when compiling.                                                                                                      | :star:         |
+| [svelte/valid-context-access](./rules/valid-context-access.md)                                                 | context functions must be called during component initialization.                                                                      |                |
 | [svelte/valid-prop-names-in-kit-pages](./rules/valid-prop-names-in-kit-pages.md)                               | disallow props other than data or errors in Svelte Kit page components.                                                                |                |
 
 ## Security Vulnerability

docs/rules/valid-context-access.md

@@ -0,0 +1,67 @@
+---
+pageClass: "rule-details"
+sidebarDepth: 0
+title: "svelte/valid-context-access"
+description: "context functions must be called during component initialization."
+---
+
+# svelte/valid-context-access
+
+> context functions must be called during component initialization.
+
+- :exclamation: <badge text="This rule has not been released yet." vertical="middle" type="error"> **_This rule has not been released yet._** </badge>
+
+## :book: Rule Details
+
+This rule reports where context API is called except during component initialization.
+
+<ESLintCodeBlock>
+
+<!--eslint-skip-->
+
+```svelte
+<script>
+  /* eslint svelte/valid-context-access: "error" */
+  import { setContext, onMount } from "svelte"
+
+  /** ✓ GOOD */
+  setContext("answer", 42)
+  ;(() => {
+    setContext("answer", 42)
+  })()
+
+  const init = () => {
+    setContext("answer", 42)
+  }
+
+  init()
+
+  /** ✗ BAD */
+  const update = () => {
+    setContext("answer", 42)
+  }
+
+  onMount(() => {
+    update()
+    setContext("answer", 42)
+  })
+</script>
+```
+
+</ESLintCodeBlock>
+
+## :wrench: Options
+
+Nothing.
+
+## :books: Further Reading
+
+- [Svelte - Docs > RUN TIME > svelte > setContext](https://svelte.dev/docs#run-time-svelte-setcontext)
+- [Svelte - Docs > RUN TIME > svelte > getContext](https://svelte.dev/docs#run-time-svelte-getContext)
+- [Svelte - Docs > RUN TIME > svelte > hasContext](https://svelte.dev/docs#run-time-svelte-hasContext)
+- [Svelte - Docs > RUN TIME > svelte > getAllContexts](https://svelte.dev/docs#run-time-svelte-getAllContexts)
+
+## :mag: Implementation
+
+- [Rule source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/src/rules/valid-context-access.ts)
+- [Test source](https://github.com/sveltejs/eslint-plugin-svelte/blob/main/tests/src/rules/valid-context-access.ts)

src/rules/reference-helpers/svelte-context.ts

@@ -0,0 +1,42 @@
+import type { TSESTree } from "@typescript-eslint/types"
+import { ReferenceTracker } from "@eslint-community/eslint-utils"
+import type { RuleContext } from "../../types"
+
+type ContextName = "setContext" | "getContext" | "hasContext" | "getAllContexts"
+
+/** Extract svelte's context API references */
+export function* extractContextReferences(
+  context: RuleContext,
+  contextNames: ContextName[] = [
+    "setContext",
+    "getContext",
+    "hasContext",
+    "getAllContexts",
+  ],
+): Generator<{ node: TSESTree.CallExpression; name: string }, void> {
+  const referenceTracker = new ReferenceTracker(
+    context.getSourceCode().scopeManager.globalScope!,
+  )
+  for (const { node, path } of referenceTracker.iterateEsmReferences({
+    svelte: {
+      [ReferenceTracker.ESM]: true,
+      setContext: {
+        [ReferenceTracker.CALL]: contextNames.includes("setContext"),
+      },
+      getContext: {
+        [ReferenceTracker.CALL]: contextNames.includes("getContext"),
+      },
+      hasContext: {
+        [ReferenceTracker.CALL]: contextNames.includes("hasContext"),
+      },
+      getAllContexts: {
+        [ReferenceTracker.CALL]: contextNames.includes("getAllContexts"),
+      },
+    },
+  })) {
+    yield {
+      node: node as TSESTree.CallExpression,
+      name: path[path.length - 1],
+    }
+  }
+}

src/rules/valid-context-access.ts

@@ -0,0 +1,113 @@
+import { createRule } from "../utils"
+import { extractContextReferences } from "./reference-helpers/svelte-context"
+import type { TSESTree } from "@typescript-eslint/types"
+
+export default createRule("valid-context-access", {
+  meta: {
+    docs: {
+      description:
+        "context functions must be called during component initialization.",
+      category: "Possible Errors",
+      // TODO Switch to recommended in the major version.
+      recommended: false,
+    },
+    schema: [],
+    messages: {
+      unexpected:
+        "Do not call {{function}} except during component initialization.",
+    },
+    type: "problem",
+  },
+  create(context) {
+    const scopeManager = context.getSourceCode().scopeManager
+    const toplevelScope =
+      scopeManager.globalScope?.childScopes.find(
+        (scope) => scope.type === "module",
+      ) || scopeManager.globalScope
+
+    /** report ESLint error */
+    function report(node: TSESTree.CallExpression) {
+      context.report({
+        loc: node.loc,
+        messageId: "unexpected",
+        data: {
+          function:
+            node.callee.type === "Identifier"
+              ? node.callee.name
+              : "context function",
+        },
+      })
+    }
+
+    /** Get nodes where the variable is used */
+    function getReferences(id: TSESTree.Identifier | TSESTree.BindingName) {
+      const variable = toplevelScope?.variables.find((v) => {
+        if (id.type === "Identifier") {
+          return v.identifiers.includes(id)
+        }
+        return false
+      })
+      if (variable) {
+        return variable.references.filter((r) => r.identifier !== id)
+      }
+      return []
+    }
+
+    /** Let's lint! */
+    function doLint(
+      visitedCallExpressions: TSESTree.CallExpression[],
+      contextCallExpression: TSESTree.CallExpression,
+      currentNode: TSESTree.CallExpression,
+    ) {
+      let { parent } = currentNode
+      if (parent?.type !== "ExpressionStatement") {
+        report(contextCallExpression)
+        return
+      }
+      while (parent) {
+        parent = parent.parent
+        if (
+          parent?.type === "VariableDeclaration" ||
+          parent?.type === "FunctionDeclaration"
+        ) {
+          const references =
+            parent.type === "VariableDeclaration"
+              ? getReferences(parent.declarations[0].id)
+              : parent.id
+              ? getReferences(parent.id)
+              : []
+
+          for (const reference of references) {
+            if (reference.identifier?.parent?.type === "CallExpression") {
+              if (
+                !visitedCallExpressions.includes(reference.identifier.parent)
+              ) {
+                visitedCallExpressions.push(reference.identifier.parent)
+                doLint(
+                  visitedCallExpressions,
+                  contextCallExpression,
+                  reference.identifier?.parent,
+                )
+              }
+            }
+          }
+        } else if (parent?.type === "ExpressionStatement") {
+          if (parent.expression.type !== "CallExpression") {
+            report(contextCallExpression)
+          } else if (parent.expression.callee.type === "Identifier") {
+            report(contextCallExpression)
+          }
+        }
+      }
+    }
+
+    return {
+      Program() {
+        for (const { node } of extractContextReferences(context)) {
+          const visitedCallExpressions: TSESTree.CallExpression[] = []
+          doLint(visitedCallExpressions, node, node)
+        }
+      },
+    }
+  },
+})

src/utils/rules.ts

@@ -57,6 +57,7 @@ import sortAttributes from "../rules/sort-attributes"
 import spacedHtmlComment from "../rules/spaced-html-comment"
 import system from "../rules/system"
 import validCompile from "../rules/valid-compile"
+import validContextAccess from "../rules/valid-context-access"
 import validEachKey from "../rules/valid-each-key"
 import validPropNamesInKitPages from "../rules/valid-prop-names-in-kit-pages"
 
@@ -116,6 +117,7 @@ export const rules = [
   spacedHtmlComment,
   system,
   validCompile,
+  validContextAccess,
   validEachKey,
   validPropNamesInKitPages,
 ] as RuleModule[]

tests/fixtures/rules/valid-context-access/invalid/case01-errors.yaml

@@ -0,0 +1,36 @@
+- message: Do not call setContext except during component initialization.
+  line: 11
+  column: 5
+- message: Do not call getContext except during component initialization.
+  line: 12
+  column: 5
+- message: Do not call hasContext except during component initialization.
+  line: 13
+  column: 5
+- message: Do not call getAllContexts except during component initialization.
+  line: 14
+  column: 5
+- message: Do not call setContext except during component initialization.
+  line: 18
+  column: 5
+- message: Do not call getContext except during component initialization.
+  line: 19
+  column: 5
+- message: Do not call hasContext except during component initialization.
+  line: 20
+  column: 5
+- message: Do not call getAllContexts except during component initialization.
+  line: 21
+  column: 5
+- message: Do not call setContext except during component initialization.
+  line: 25
+  column: 5
+- message: Do not call getContext except during component initialization.
+  line: 26
+  column: 5
+- message: Do not call hasContext except during component initialization.
+  line: 27
+  column: 5
+- message: Do not call getAllContexts except during component initialization.
+  line: 28
+  column: 5

tests/fixtures/rules/valid-context-access/invalid/case01-input.svelte

@@ -0,0 +1,36 @@
+<script>
+  import {
+    setContext,
+    getContext,
+    hasContext,
+    getAllContexts,
+    onMount,
+  } from "svelte"
+
+  const update1 = () => {
+    setContext("answer", 42)
+    getContext("answer")
+    hasContext("answer")
+    getAllContexts()
+  }
+
+  const update2 = function () {
+    setContext("answer", 42)
+    getContext("answer")
+    hasContext("answer")
+    getAllContexts()
+  }
+
+  function update3() {
+    setContext("answer", 42)
+    getContext("answer")
+    hasContext("answer")
+    getAllContexts()
+  }
+
+  onMount(() => {
+    update1()
+    update2()
+    update3()
+  })
+</script>

tests/fixtures/rules/valid-context-access/invalid/case02-errors.yaml

@@ -0,0 +1,3 @@
+- message: Do not call setContext except during component initialization.
+  line: 5
+  column: 5

tests/fixtures/rules/valid-context-access/invalid/case02-input.svelte

@@ -0,0 +1,7 @@
+<script>
+  import { setContext, onMount } from "svelte"
+
+  onMount(() => {
+    setContext("answer", 42)
+  })
+</script>

tests/fixtures/rules/valid-context-access/invalid/case03-errors.yaml

@@ -0,0 +1,4 @@
+- message: Do not call setContext except during component initialization.
+  line: 4
+  column: 5
+  suggestions: null

tests/fixtures/rules/valid-context-access/invalid/case03-input.svelte

@@ -0,0 +1,10 @@
+<script>
+  import { setContext, onMount } from "svelte"
+  const something = () => {
+    setContext("answer", 42)
+  }
+
+  something()
+</script>
+
+<button on:click={() => something()}>Click Me</button>

tests/fixtures/rules/valid-context-access/invalid/case04-errors.yaml

@@ -0,0 +1,4 @@
+- message: Do not call setContext except during component initialization.
+  line: 4
+  column: 5
+  suggestions: null

tests/fixtures/rules/valid-context-access/invalid/case04-input.svelte

@@ -0,0 +1,13 @@
+<script>
+  import { setContext, onMount } from "svelte"
+  const something = () => {
+    setContext("answer", 42)
+  }
+
+  something()
+</script>
+
+{#if true}
+  {@const foo = something()}
+  <button>Click Me</button>
+{/if}

tests/fixtures/rules/valid-context-access/invalid/case05-errors.yaml

@@ -0,0 +1,4 @@
+- message: Do not call setContext except during component initialization.
+  line: 4
+  column: 5
+  suggestions: null

tests/fixtures/rules/valid-context-access/invalid/case05-input.svelte

@@ -0,0 +1,12 @@
+<script>
+  import { setContext, onMount } from "svelte"
+  const something = () => {
+    setContext("answer", 42)
+  }
+
+  something()
+</script>
+
+{#if something()}
+  <button>Click Me</button>
+{/if}