goImports: avoid collapsing new imports into pseudo import line (#3045)

* goImports: avoid collapsing new imports into pseudo import line

getTextEditForAddImport tries to insert a newly added package
into an existing import group. If no import group exists, it
tries to merge single line import statements and create a group.

In this process, import statements like

  import "C"

are pseudo imports and shouldn't be grouped with other imports.
This CL changes parseFilePrelude to detect such pseudo imports
and excludes such imports from the grouping logic.

Fixes #1701

* correct the file name

mac and vsccode ignored casing, but linux and git were unhappy.

src/goImport.ts

@@ -83,6 +83,8 @@ export function getTextEditForAddImport(arg: string): vscode.TextEdit[] {
 	}
 
 	const multis = imports.filter((x) => x.kind === 'multi');
+	const minusCgo = imports.filter((x) => x.kind !== 'pseudo');
+
 	if (multis.length > 0) {
 		// There is a multiple import declaration, add to the last one
 		const lastImportSection = multis[multis.length - 1];
@@ -92,12 +94,12 @@ export function getTextEditForAddImport(arg: string): vscode.TextEdit[] {
 		}
 		// Add import at the start of the block so that goimports/goreturns can order them correctly
 		return [vscode.TextEdit.insert(new vscode.Position(lastImportSection.start + 1, 0), '\t"' + arg + '"\n')];
-	} else if (imports.length > 0) {
+	} else if (minusCgo.length > 0) {
 		// There are some number of single line imports, which can just be collapsed into a block import.
 		const edits = [];
 
-		edits.push(vscode.TextEdit.insert(new vscode.Position(imports[0].start, 0), 'import (\n\t"' + arg + '"\n'));
-		imports.forEach((element) => {
+		edits.push(vscode.TextEdit.insert(new vscode.Position(minusCgo[0].start, 0), 'import (\n\t"' + arg + '"\n'));
+		minusCgo.forEach((element) => {
 			const currentLine = vscode.window.activeTextEditor.document.lineAt(element.start).text;
 			const updatedLine = currentLine.replace(/^\s*import\s*/, '\t');
 			edits.push(
@@ -107,7 +109,7 @@ export function getTextEditForAddImport(arg: string): vscode.TextEdit[] {
 				)
 			);
 		});
-		edits.push(vscode.TextEdit.insert(new vscode.Position(imports[imports.length - 1].end + 1, 0), ')\n'));
+		edits.push(vscode.TextEdit.insert(new vscode.Position(minusCgo[minusCgo.length - 1].end + 1, 0), ')\n'));
 
 		return edits;
 	} else if (pkg && pkg.start >= 0) {

src/util.ts

@@ -156,11 +156,12 @@ export function parseFilePrelude(text: string): Prelude {
 		}
 		if (line.match(/^(\s)*import(\s)+\(/)) {
 			ret.imports.push({ kind: 'multi', start: i, end: -1, pkgs: [] });
-		}
-		if (line.match(/^(\s)*import(\s)+[^\(]/)) {
+		} else if (line.match(/^\s*import\s+"C"/)) {
+			ret.imports.push({ kind: 'pseudo', start: i, end: i, pkgs: [] });
+		} else if (line.match(/^(\s)*import(\s)+[^\(]/)) {
 			ret.imports.push({ kind: 'single', start: i, end: i, pkgs: [] });
 		}
-		if (line.match(/^(\s)*(\/\*.*\*\/)*\s*\)/)) {
+		if (line.match(/^(\s)*(\/\*.*\*\/)*\s*\)/)) {  // /* comments */
 			if (ret.imports[ret.imports.length - 1].end === -1) {
 				ret.imports[ret.imports.length - 1].end = i;
 			}

test/fixtures/importTest/cgoImports.go

@@ -0,0 +1,10 @@
+package main
+
+//#include <stdlib.h>
+import "C"
+
+import "math"
+
+func main() {
+	_ = math.Max(1, 2)
+}

test/integration/extension.test.ts

@@ -162,6 +162,10 @@ suite('Go Extension Tests', function () {
 			path.join(fixtureSourcePath, 'importTest', 'singleImports.go'),
 			path.join(fixturePath, 'importTest', 'singleImports.go')
 		);
+		fs.copySync(
+			path.join(fixtureSourcePath, 'importTest', 'cgoImports.go'),
+			path.join(fixturePath, 'importTest', 'cgoImports.go')
+		);
 		fs.copySync(
 			path.join(fixtureSourcePath, 'fillStruct', 'input_1.go'),
 			path.join(fixturePath, 'fillStruct', 'input_1.go')
@@ -1590,6 +1594,24 @@ encountered.
 		assert.equal(vscode.window.activeTextEditor && vscode.window.activeTextEditor.document.getText(), expectedText);
 	});
 
+	test('Add imports and avoid pseudo package imports for cgo', async () => {
+		const uri = vscode.Uri.file(path.join(fixturePath, 'importTest', 'cgoImports.go'));
+		const document = await vscode.workspace.openTextDocument(uri);
+		await vscode.window.showTextDocument(document);
+
+		const expectedText = document
+			.getText()
+			.replace(
+				'import "math"',
+				'import (\n\t"bytes"\n\t"math"\n)'
+			);
+		const edits = getTextEditForAddImport('bytes');
+		const edit = new vscode.WorkspaceEdit();
+		edit.set(document.uri, edits);
+		await vscode.workspace.applyEdit(edit);
+		assert.equal(vscode.window.activeTextEditor && vscode.window.activeTextEditor.document.getText(), expectedText);
+	});
+
 	test('Fill struct', async () => {
 		const uri = vscode.Uri.file(path.join(fixturePath, 'fillStruct', 'input_1.go'));
 		const golden = fs.readFileSync(path.join(fixturePath, 'fillStruct', 'golden_1.go'), 'utf-8');