fix(eslint-plugin): [init-declarations] refine report locations (#8893)

[init-declarations] refine report loc
typescript-eslint · Jun 5, 2024 · fbff4ce · fbff4ce
1 parent a87ce50
commit fbff4ce
Show file tree

Hide file tree

Showing 2 changed files with 196 additions and 35 deletions.
diff --git a/packages/eslint-plugin/src/rules/init-declarations.ts b/packages/eslint-plugin/src/rules/init-declarations.ts
@@ -28,7 +28,51 @@ export default createRule<Options, MessageIds>({
   },
   defaultOptions: ['always'],
   create(context, [mode]) {
-    const rules = baseRule.create(context);
+    // Make a custom context to adjust the the loc of reports where the base
+    // rule's behavior is a bit too aggressive with TS-specific syntax (namely,
+    // type annotations).
+    function getBaseContextOverride(): typeof context {
+      const reportOverride: typeof context.report = descriptor => {
+        if ('node' in descriptor && descriptor.loc == null) {
+          const { node, ...rest } = descriptor;
+          // We only want to special case the report loc when reporting on
+          // variables declarations that are not initialized. Declarations that
+          // _are_ initialized get reported by the base rule due to a setting to
+          // prohibit initializing variables entirely, in which case underlining
+          // the whole node including the type annotation and initializer is
+          // appropriate.
+          if (
+            node.type === AST_NODE_TYPES.VariableDeclarator &&
+            node.init == null
+          ) {
+            context.report({
+              ...rest,
+              loc: getReportLoc(node),
+            });
+            return;
+          }
+        }
+
+        context.report(descriptor);
+      };
+
+      // `return { ...context, report: reportOverride }` isn't safe because the
+      // `context` object has some getters that need to be preserved.
+      //
+      // `return new Proxy(context, ...)` doesn't work because `context` has
+      // non-configurable properties that throw when constructing a Proxy.
+      //
+      // So, we'll just use Proxy on a dummy object and use the `get` trap to
+      // proxy `context`'s properties.
+      return new Proxy({} as typeof context, {
+        get: (target, prop, receiver): unknown =>
+          prop === 'report'
+            ? reportOverride
+            : Reflect.get(context, prop, receiver),
+      });
+    }
+
+    const rules = baseRule.create(getBaseContextOverride());
 
     return {
       'VariableDeclaration:exit'(node: TSESTree.VariableDeclaration): void {
@@ -65,3 +109,26 @@ export default createRule<Options, MessageIds>({
     }
   },
 });
+
+/**
+ * When reporting an uninitialized variable declarator, get the loc excluding
+ * the type annotation.
+ */
+function getReportLoc(
+  node: TSESTree.VariableDeclarator,
+): TSESTree.SourceLocation {
+  const start: TSESTree.Position = structuredClone(node.loc.start);
+  const end: TSESTree.Position = {
+    line: node.loc.start.line,
+    // `if (id.type === AST_NODE_TYPES.Identifier)` is a condition for
+    // reporting in the base rule (as opposed to things like destructuring
+    // assignment), so the type assertion should always be valid.
+    column:
+      node.loc.start.column + (node.id as TSESTree.Identifier).name.length,
+  };
+
+  return {
+    start,
+    end,
+  };
+}