Extensions can reverse order of TextDocumentChangeEvent.contentChanges causing other extensions documents to become out of sync

[bmewburn]

Version: 1.41.1
Commit: 26076a4
Date: 2019-12-18T15:04:31.999Z
Electron: 6.1.5
Chrome: 76.0.3809.146
Node.js: 12.4.0
V8: 7.6.303.31-electron.0
OS: Linux x64 4.19.0-6-amd64

Steps to Reproduce:

1. Install https://marketplace.visualstudio.com/items?itemName=austenc.laravel-blade-spacer
2. Install another extension that has TextDocumentSyncKind.Incremental support. eg https://marketplace.visualstudio.com/items?itemName=bmewburn.vscode-intelephense-client
3. Turn server trace to verbose.
4. Edit the document then undo those changes.
5. Spurious errors can be observed indicating document is out of sync if diagnostics are supported.
6. Try same edits without the extension in step 1 and compare server traces and observe that changes sent to the server are reversed.

See https://github.com/austenc/vscode-blade-spacer/blob/ae88ae1e82719c7b9fc088b93903285ac61b283a/src/extension.ts#L35 . Expected result would be that an extension doing this would not be able to affect other extensions.

According to the LSP spec the order is important.
https://microsoft.github.io/language-server-protocol/specifications/specification-3-14/#textDocument_didChange

/**
	 * The actual content changes. The content changes describe single state changes
	 * to the document. So if there are two content changes c1 and c2 for a document
	 * in state S then c1 move the document to S' and c2 to S''.
	 */

server trace

**REVERSED**
[Trace - 9:07:06 am] Sending notification 'textDocument/didChange'.
Params: {
    "textDocument": {
        "uri": "file:///home/ben/Projects/laravel-test/app/User.php",
        "version": 19
    },
    "contentChanges": [
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 31
                },
                "end": {
                    "line": 13,
                    "character": 32
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 32
                },
                "end": {
                    "line": 13,
                    "character": 33
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 33
                },
                "end": {
                    "line": 13,
                    "character": 34
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 34
                },
                "end": {
                    "line": 13,
                    "character": 35
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 35
                },
                "end": {
                    "line": 13,
                    "character": 36
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 13,
                    "character": 36
                },
                "end": {
                    "line": 13,
                    "character": 37
                }
            },
            "rangeLength": 1,
            "text": ""
        }
    ]
}

**NOT REVERSED**
[Trace - 9:11:25 am] Sending notification 'textDocument/didChange'.
Params: {
    "textDocument": {
        "uri": "file:///home/ben/Projects/laravel-test/app/User.php",
        "version": 25
    },
    "contentChanges": [
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 36
                },
                "end": {
                    "line": 15,
                    "character": 37
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 35
                },
                "end": {
                    "line": 15,
                    "character": 36
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 34
                },
                "end": {
                    "line": 15,
                    "character": 35
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 33
                },
                "end": {
                    "line": 15,
                    "character": 34
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 32
                },
                "end": {
                    "line": 15,
                    "character": 33
                }
            },
            "rangeLength": 1,
            "text": ""
        },
        {
            "range": {
                "start": {
                    "line": 15,
                    "character": 31
                },
                "end": {
                    "line": 15,
                    "character": 32
                }
            },
            "rangeLength": 1,
            "text": ""
        }
    ]
}

Does this issue occur when all extensions are disabled?: Extensions are needed to observe error.

[dbaeumer]

@bmewburn good catch.

@jrieken very interesting case. Can we freeze the array to avoid that extensions mess with the event?

[dbaeumer]

@alexdima FYI.