[Fix] no-duplicates: ensure autofix avoids excessive newlines

Fixes #2027

Author: ertrzyiks

Diff for: CHANGELOG.md

@@ -31,6 +31,7 @@ This change log adheres to standards from [Keep a CHANGELOG](http://keepachangel
 - [`newline-after-import`]: respect decorator annotations ([#1985], thanks [@lilling])
 - [`no-restricted-paths`]: enhance performance for zones with `except` paths ([#2022], thanks [@malykhinvi])
 - [`no-unresolved`]: check import() ([#2026], thanks [@aladdin-add])
+- [`no-duplicates`]: ensure autofix avoids excessive newlines ([#2028], thanks [@ertrzyiks])
 
 ### Changed
 - [Generic Import Callback] Make callback for all imports once in rules ([#1237], thanks [@ljqx])
@@ -770,6 +771,7 @@ for info on changes for earlier releases.
 [`memo-parser`]: ./memo-parser/README.md
 
 [#2034]: https://github.com/benmosher/eslint-plugin-import/pull/2034
+[#2028]: https://github.com/benmosher/eslint-plugin-import/pull/2028
 [#2026]: https://github.com/benmosher/eslint-plugin-import/pull/2026
 [#2022]: https://github.com/benmosher/eslint-plugin-import/pull/2022
 [#2021]: https://github.com/benmosher/eslint-plugin-import/pull/2021
@@ -1368,4 +1370,5 @@ for info on changes for earlier releases.
 [@aladdin-add]: https://github.com/aladdin-add
 [@davidbonnet]: https://github.com/davidbonnet
 [@hayes]: https://github.com/hayes
-[@edemaine]: https://github.com/edemaine
+[@edemaine]: https://github.com/edemaine
+[@ertrzyiks]: https://github.com/ertrzyiks

Diff for: src/rules/no-duplicates.js

@@ -150,14 +150,27 @@ function getFix(first, rest, sourceCode) {
 
     // Remove imports whose specifiers have been moved into the first import.
     for (const specifier of specifiers) {
-      fixes.push(fixer.remove(specifier.importNode));
+      const importNode = specifier.importNode;
+      fixes.push(fixer.remove(importNode));
+
+      const charAfterImportRange = [importNode.range[1], importNode.range[1] + 1]
+      const charAfterImport = sourceCode.text.substring(charAfterImportRange[0], charAfterImportRange[1]);
+      if (charAfterImport === '\n') {
+        fixes.push(fixer.removeRange(charAfterImportRange));
+      }
     }
 
     // Remove imports whose default import has been moved to the first import,
     // and side-effect-only imports that are unnecessary due to the first
     // import.
     for (const node of unnecessaryImports) {
       fixes.push(fixer.remove(node));
+
+      const charAfterImportRange = [node.range[1], node.range[1] + 1];
+      const charAfterImport = sourceCode.text.substring(charAfterImportRange[0], charAfterImportRange[1]);
+      if (charAfterImport === '\n') {
+        fixes.push(fixer.removeRange(charAfterImportRange));
+      }
     }
 
     return fixes;

Diff for: tests/src/rules/no-duplicates.js

@@ -400,6 +400,21 @@ ruleTester.run('no-duplicates', rule, {
       `,
       errors: ['\'./foo\' imported multiple times.', '\'./foo\' imported multiple times.'],
     }),
+
+
+    // #2027 long import list generate empty lines
+    test({
+      code: "import { Foo } from './foo';\nimport { Bar } from './foo';\nexport const value = {}",
+      output: "import { Foo , Bar } from './foo';\nexport const value = {}",
+      errors: ['\'./foo\' imported multiple times.', '\'./foo\' imported multiple times.'],
+    }),
+
+    // #2027 long import list generate empty lines
+    test({
+      code: "import { Foo } from './foo';\nimport Bar from './foo';\nexport const value = {}",
+      output: "import Bar, { Foo } from './foo';\nexport const value = {}",
+      errors: ['\'./foo\' imported multiple times.', '\'./foo\' imported multiple times.'],
+    }),
   ],
 });
 
@@ -430,4 +445,3 @@ context('TypeScript', function() {
       });
     });
 });
-