fix casing from canonical uri

src/helper/paths.ts

@@ -1,15 +1,36 @@
 import * as os from 'os';
 import * as path from 'path';
+import * as fs from 'fs';
+import { URI } from 'vscode-uri';
 import { upath } from '../core';
 import { pathRelativeToWorkspace, getWorkspaceFolders } from '../host';
 
+// from https://github.com/microsoft/vscode-eslint/blob/d97a8b5e99ad30d2ce32ffa5646447202f873413/server/src/eslintServer.ts#L816
+function getFileSystemPath(uri: URI): string {
+	let result = uri.fsPath;
+	if (process.platform === 'win32' && result.length >= 2 && result[1] === ':') {
+		// Node by default uses an upper case drive letter and ESLint uses
+		// === to compare paths which results in the equal check failing
+		// if the drive letter is lower case in th URI. Ensure upper case.
+		result = result[0].toUpperCase() + result.substr(1);
+	}
+	if (process.platform === 'win32' || process.platform === 'darwin') {
+		const realpath = fs.realpathSync.native(result);
+		// Only use the real path if only the casing has changed.
+		if (realpath.toLowerCase() === result.toLowerCase()) {
+			result = realpath;
+		}
+	}
+	return result;
+}
+
 export function simplifyPath(absolutePath: string) {
   return pathRelativeToWorkspace(absolutePath);
 }
 
 // FIXME: use fs.pathResolver instead of upath
 export function toRemotePath(localPath: string, localContext: string, remoteContext: string) {
-  return upath.join(remoteContext, path.relative(localContext, localPath));
+  return upath.join(remoteContext, path.relative(getFileSystemPath(localContext), getFileSystemPath(localPath)));
 }
 
 // FIXME: use fs.pathResolver instead of upath