fix(no-topromise): don't try to fix zero import files

Likely someone is spoofing Observable or maybe RxJS has been embedded in the file?  Weird edge case that we don't need to handle.

Author: JasonWeinzierl

src/rules/no-topromise.ts

@@ -35,14 +35,12 @@ export const noTopromiseRule = ruleCreator({
       conversion: 'lastValueFrom' | 'firstValueFrom',
       callExpression: es.CallExpression,
       observableNode: es.Node,
+      importDeclarations: es.ImportDeclaration[],
     ) {
       return function* fix(fixer: TSESLint.RuleFixer) {
         let namespace = '';
         let functionName: string = conversion;
 
-        const { body } = context.sourceCode.ast;
-        const importDeclarations = body.filter(isImportDeclaration);
-
         const rxjsImportDeclaration = importDeclarations.find(node => node.source.value === 'rxjs');
 
         if (rxjsImportDeclaration?.specifiers?.every(isImportNamespaceSpecifier)) {
@@ -69,11 +67,8 @@ export const noTopromiseRule = ruleCreator({
             `\nimport { ${functionName} } from ${quote}rxjs${quote};`,
           );
         } else {
-          // No imports. Add to top of file.
-          yield fixer.insertTextBefore(
-            body[0],
-            `import { ${functionName} } from "rxjs";\n`,
-          );
+          console.warn('No import declarations found. Unable to suggest a fix.');
+          return;
         }
 
         yield fixer.replaceText(
@@ -91,17 +86,25 @@ export const noTopromiseRule = ruleCreator({
         if (!couldBeObservable(memberExpression.object)) {
           return;
         }
+
+        const { body } = context.sourceCode.ast;
+        const importDeclarations = body.filter(isImportDeclaration);
+        if (!importDeclarations.length) {
+          // couldBeObservable yet no imports? Skip.
+          return;
+        }
+
         context.report({
           messageId: 'forbidden',
           node: memberExpression.property,
           suggest: [
             {
               messageId: 'suggestLastValueFrom',
-              fix: createFix('lastValueFrom', node, memberExpression.object),
+              fix: createFix('lastValueFrom', node, memberExpression.object, importDeclarations),
             },
             {
               messageId: 'suggestFirstValueFrom',
-              fix: createFix('firstValueFrom', node, memberExpression.object),
+              fix: createFix('firstValueFrom', node, memberExpression.object, importDeclarations),
             },
           ],
         });

tests/rules/no-topromise.test.ts

@@ -20,6 +20,16 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
       };
       a.toPromise().then(value => console.log(value));
     `,
+    stripIndent`
+      // no imports
+      class Observable {
+        toPromise() {
+          return Promise.resolve("a");
+        }
+      }
+      const a = new Observable();
+      a.toPromise().then(value => console.log(value));
+    `,
   ],
   invalid: [
     fromFixture(
@@ -220,50 +230,5 @@ ruleTester({ types: true }).run('no-topromise', noTopromiseRule, {
         ],
       },
     ),
-    fromFixture(
-      stripIndent`
-        // no imports
-        class Observable {
-          toPromise() {
-            return Promise.resolve("a");
-          }
-        }
-        const a = new Observable();
-        a.toPromise().then(value => console.log(value));
-          ~~~~~~~~~ [forbidden suggest 0 1]
-      `,
-      {
-        suggestions: [
-          {
-            messageId: 'suggestLastValueFrom',
-            output: stripIndent`
-              // no imports
-              import { lastValueFrom } from "rxjs";
-              class Observable {
-                toPromise() {
-                  return Promise.resolve("a");
-                }
-              }
-              const a = new Observable();
-              lastValueFrom(a).then(value => console.log(value));
-            `,
-          },
-          {
-            messageId: 'suggestFirstValueFrom',
-            output: stripIndent`
-              // no imports
-              import { firstValueFrom } from "rxjs";
-              class Observable {
-                toPromise() {
-                  return Promise.resolve("a");
-                }
-              }
-              const a = new Observable();
-              firstValueFrom(a).then(value => console.log(value));
-            `,
-          },
-        ],
-      },
-    ),
   ],
 });