Fix microsoft#2551 : Code coverage disappears when typing a character

This also preserves an earlier fix to keep coverage when the modifications
are only due to comment edits.

Supersedes microsoft#2586

src/goCover.ts

@@ -29,6 +29,10 @@ let decoratorConfig: {
 	coveredGutterStyle: string;
 	uncoveredGutterStyle: string;
 };
+// a list of modified, unsaved go files with actual code edits (rather than comment edits)
+let modifiedFiles: {
+	[key: string]: boolean;
+};
 
 /**
  * Initializes the decorators used for Code coverage.
@@ -255,12 +259,33 @@ export function applyCodeCoverage(editor: vscode.TextEditor) {
 	}
 }
 
+/**
+ * Listener for file save
+ * A save in a Go file means the coverage data is stale, if it is dirty and the diff
+ * is in code and not comments. Therefore it should be cleared.
+ * @param e TextDocument
+ */
+export function removeCodeCoverageOnFileSave(e: vscode.TextDocument) {
+	if (e.languageId !== 'go' || !isCoverageApplied || !e.isDirty) {
+		return;
+	}
+
+	if (vscode.window.visibleTextEditors.every(editor => editor.document !== e)) {
+		return;
+	}
+
+	if (modifiedFiles[e.fileName]) {
+		clearCoverage();
+		modifiedFiles = {}; // reset the list of modified files
+	}
+}
+
 /**
  * Listener for change in the editor.
- * A change in a Go file means the coverage data is stale. Therefore it should be cleared.
+ * A change in a Go file means the coverage data is stale. Therefore it should be cleared on save.
  * @param e TextDocumentChangeEvent
  */
-export function removeCodeCoverageOnFileChange(e: vscode.TextDocumentChangeEvent) {
+export function trackCodeCoverageRemovalOnFileChange(e: vscode.TextDocumentChangeEvent) {
 	if (e.document.languageId !== 'go' || !e.contentChanges.length || !isCoverageApplied) {
 		return;
 	}
@@ -273,7 +298,7 @@ export function removeCodeCoverageOnFileChange(e: vscode.TextDocumentChangeEvent
 		return;
 	}
 
-	clearCoverage();
+	modifiedFiles[e.document.fileName] = true;
 }
 
 /**

src/goMain.ts

@@ -10,7 +10,7 @@ import { browsePackages } from './goBrowsePackage';
 import { buildCode } from './goBuild';
 import { check, notifyIfGeneratedFile, removeTestStatus } from './goCheck';
 import { GoCodeActionProvider } from './goCodeAction';
-import { applyCodeCoverage, initCoverageDecorators, removeCodeCoverageOnFileChange, toggleCoverageCurrentPackage, updateCodeCoverageDecorators } from './goCover';
+import { applyCodeCoverage, initCoverageDecorators, trackCodeCoverageRemovalOnFileChange, removeCodeCoverageOnFileSave, toggleCoverageCurrentPackage, updateCodeCoverageDecorators } from './goCover';
 import { GoDebugConfigurationProvider } from './goDebugConfiguration';
 import { extractFunction, extractVariable } from './goDoctor';
 import { runFillStruct } from './goFillStruct';
@@ -385,6 +385,7 @@ function runBuilds(document: vscode.TextDocument, goConfig: vscode.WorkspaceConf
 }
 
 function addOnSaveTextDocumentListeners(ctx: vscode.ExtensionContext) {
+	vscode.workspace.onDidSaveTextDocument(removeCodeCoverageOnFileSave, null, ctx.subscriptions);
 	vscode.workspace.onDidSaveTextDocument(document => {
 		if (document.languageId !== 'go') {
 			return;
@@ -400,7 +401,7 @@ function addOnSaveTextDocumentListeners(ctx: vscode.ExtensionContext) {
 }
 
 function addOnChangeTextDocumentListeners(ctx: vscode.ExtensionContext) {
-	vscode.workspace.onDidChangeTextDocument(removeCodeCoverageOnFileChange, null, ctx.subscriptions);
+	vscode.workspace.onDidChangeTextDocument(trackCodeCoverageRemovalOnFileChange, null, ctx.subscriptions);
 	vscode.workspace.onDidChangeTextDocument(removeTestStatus, null, ctx.subscriptions);
 	vscode.workspace.onDidChangeTextDocument(notifyIfGeneratedFile, ctx, ctx.subscriptions);
 }