Pressing enter only results in inserting a newline after more than half a minute

[Wodann]

After installing the latest version of rust analyzer, I noticed that pressing Enter (either the default or numpad Enter) doesn't result in a newline. After a seemingly arbitrary delay of over 30 seconds, a new line is inserted after all.

I also tried copying and pasting a newline, which works without any trouble.

It seems like it is a regression from my previous install (last week). Currently I am on commit 91bd783273477d.

[memoryruins]

Assuming vscode, is there anything showing in the output / traces?
Was it a normal project and/or something similar to the case in #1259?

[DJMcNab]

I sometimes get this. A temporary workaround of using ctrl+enter rather than just ctrl has worked for me.

[Wodann]

@memoryruins Yes, it is vscode. Sorry for not mentioning that.

I had a look at issue #1259. I am not sure whether there is any difference between his project or mine. I have a workspace crate that contains four crates, which are used as dependencies amongst each other (very similar to RA's structure)

The reported error seems different from #1259 though. From what I could determine from the log, it consistently takes about 15 seconds for the server to respond to a request. Sometimes the server reports that the client cancelled a request. The reception of a response doesn't directly result in the addition of a newline. Eventually all enters are processed and cause newlines to occur at the original location of execution.

Some additional observations:

• Before the Start watching changes with cargo? pops up, I can briefly press enter.
• It does seem like RA is capable of "recovering" from this issue as after leaving RA unmanaged for some time it can randomly happen that enters start and keep responding directly.

This is just me hypothesizing, but it almost seems like some work is happening in the background that stalls requests. As requests start racking up, this causes further delays. When left for a while, the queue slowly empties. After this further requests can happen directly again.

Could it maybe be caused by the initial loading of modules, as that might take some time. It's weird that I can type other symbols than Enter without any issues though.

@DJMcNab Thank you! Pressing Ctrl + Enter actually works :)

The trace reports the following:

EDIT(@matklad): hide the trace under <details>

``` [Trace - 18:23:04] Sending request 'rust-analyzer/onEnter - (38)'. Params: { "textDocument": { "uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs" }, "position": { "line": 26, "character": 5 } }

[Trace - 18:23:16] Received response 'textDocument/codeAction - (29)' in 13268ms. Request failed: canceled by client (-32800).
[Trace - 18:23:16] Received response 'textDocument/foldingRange - (24)' in 14608ms. Request failed: canceled by client (-32800).
[Trace - 18:23:16] Received response 'textDocument/codeAction - (30)' in 12909ms. Request failed: canceled by client (-32800).
[Trace - 18:23:18] Received response 'textDocument/documentSymbol - (28)' in 16663ms.
Result: [
{
"deprecated": false,
"kind": 2,
"name": "tests",
"range": {
"end": {
"character": 12,
"line": 41
},
"start": {
"character": 0,
"line": 40
}
},
"selectionRange": {
"end": {
"character": 9,
"line": 41
},
"start": {
"character": 4,
"line": 41
}
}
},
{
"children": [
{
"deprecated": false,
"detail": "fn(&self, name: &str, user: &str, pwd: &str) -> DbResult",
"kind": 12,
"name": "auth_db",
"range": {
"end": {
"character": 5,
"line": 37
},
"start": {
"character": 4,
"line": 31
}
},
"selectionRange": {
"end": {
"character": 18,
"line": 31
},
"start": {
"character": 11,
"line": 31
}
}
},
{
"deprecated": false,
"detail": "fn(address: &str, port: u16, options: Option) -> DbResult",
"kind": 12,
"name": "connect",
"range": {
"end": {
"character": 5,
"line": 26
},
"start": {
"character": 4,
"line": 19
}
},
"selectionRange": {
"end": {
"character": 18,
"line": 19
},
"start": {
"character": 11,
"line": 19
}
}
}
],
"deprecated": false,
"kind": 19,
"name": "impl DbServer",
"range": {
"end": {
"character": 1,
"line": 38
},
"start": {
"character": 0,
"line": 18
}
},
"selectionRange": {
"end": {
"character": 13,
"line": 18
},
"start": {
"character": 5,
"line": 18
}
}
},
{
"children": [
{
"deprecated": false,
"detail": "gridfs::Store",
"kind": 8,
"name": "fs",
"range": {
"end": {
"character": 25,
"line": 15
},
"start": {
"character": 4,
"line": 15
}
},
"selectionRange": {
"end": {
"character": 10,
"line": 15
},
"start": {
"character": 8,
"line": 15
}
}
},
{
"deprecated": false,
"detail": "mongodb::db::Database",
"kind": 8,
"name": "db",
"range": {
"end": {
"character": 33,
"line": 14
},
"start": {
"character": 4,
"line": 14
}
},
"selectionRange": {
"end": {
"character": 10,
"line": 14
},
"start": {
"character": 8,
"line": 14
}
}
}
],
"deprecated": false,
"kind": 23,
"name": "DbClient",
"range": {
"end": {
"character": 1,
"line": 16
},
"start": {
"character": 0,
"line": 13
}
},
"selectionRange": {
"end": {
"character": 19,
"line": 13
},
"start": {
"character": 11,
"line": 13
}
}
},
{
"children": [
{
"deprecated": false,
"detail": "Client",
"kind": 8,
"name": "client",
"range": {
"end": {
"character": 18,
"line": 10
},
"start": {
"character": 4,
"line": 10
}
},
"selectionRange": {
"end": {
"character": 10,
"line": 10
},
"start": {
"character": 4,
"line": 10
}
}
}
],
"deprecated": false,
"kind": 23,
"name": "DbServer",
"range": {
"end": {
"character": 1,
"line": 11
},
"start": {
"character": 0,
"line": 9
}
},
"selectionRange": {
"end": {
"character": 19,
"line": 9
},
"start": {
"character": 11,
"line": 9
}
}
}
]

[Trace - 18:23:18] Received response 'textDocument/codeLens - (27)' in 16760ms.
Result: [
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 9
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 11
},
"start": {
"character": 0,
"line": 9
}
}
},
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 13
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 16
},
"start": {
"character": 0,
"line": 13
}
}
}
]

[Trace - 18:23:18] Received response 'textDocument/codeLens - (26)' in 16762ms.
Result: [
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 9
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 11
},
"start": {
"character": 0,
"line": 9
}
}
},
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 13
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 16
},
"start": {
"character": 0,
"line": 13
}
}
}
]

[Trace - 18:23:18] Received response 'codeLens/resolve - (25)' in 16762ms. Request failed: canceled by client (-32800).
[Trace - 18:23:18] Received response 'textDocument/foldingRange - (31)' in 14816ms.
Result: [
{
"endCharacter": 0,
"endLine": 5,
"kind": "imports",
"startCharacter": 0,
"startLine": 2
},
{
"endCharacter": 20,
"endLine": 11,
"startCharacter": 20,
"startLine": 9
},
{
"endCharacter": 20,
"endLine": 16,
"startCharacter": 20,
"startLine": 13
},
{
"endCharacter": 14,
"endLine": 35,
"startCharacter": 14,
"startLine": 18
},
{
"endCharacter": 99,
"endLine": 26,
"startCharacter": 99,
"startLine": 19
},
{
"endCharacter": 83,
"endLine": 34,
"startCharacter": 83,
"startLine": 28
}
]

[Trace - 18:23:18] Received response 'textDocument/codeLens - (33)' in 14768ms.
Result: [
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 9
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 11
},
"start": {
"character": 0,
"line": 9
}
}
},
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 13
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 16
},
"start": {
"character": 0,
"line": 13
}
}
}
]

[Trace - 18:23:18] Received response 'textDocument/codeLens - (35)' in 14765ms.
Result: [
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 9
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 11
},
"start": {
"character": 0,
"line": 9
}
}
},
{
"data": {
"impls": {
"position": {
"character": 0,
"line": 13
},
"textDocument": {
"uri": "file:///e%3A/dev/src/se4_core/crates/se4_db/src/lib.rs"
}
}
},
"range": {
"end": {
"character": 1,
"line": 16
},
"start": {
"character": 0,
"line": 13
}
}
}
]

[Trace - 18:23:18] Received response 'rust-analyzer/onEnter - (37)' in 14589ms.
No result returned.

[Trace - 18:23:18] Received response 'rust-analyzer/onEnter - (38)' in 14357ms.
No result returned.

</details>

[DJMcNab]

No problem! I'm afraid I can't really help with the underlying issue.

[matklad]

It's a know problem, I hope to look into this soon.

The crux of the issue is that we don't implement any kind of request prioritization, so things like "handle enter" could be blocked on the background analysis

[sophiajt]

@matklad - I'm still seeing this issue with the latest rust-analyzer

[kiljacken]

I'm also experiencing this issue quite commonly. Will gladly help if pointed in the right direction :)

[matklad]

@kiljacken the steps to handle this problem:

• find out why it is slow, by inserting profile("foo") calls
• write a heavy test that shows the issue
• implement a fix

#1334 contains all those steps

Docs for our profiling infra are here: https://github.com/rust-analyzer/rust-analyzer/blob/master/docs/dev/README.md#profiling

[matklad]

To clarify, on the high level, the problem isn't that handling Enter is slow, the problem is that handling Enter is blocked on some other stuff, and we should make sure that "other stuff" is properly canceled or does not block high-priority operations in the first place.

Another pointer would be our main loop:

https://github.com/rust-analyzer/rust-analyzer/blob/9eef546ca2f59d0ebc0e5dc443fc1a5d93926030/crates/ra_lsp_server/src/main_loop.rs#L172

Here, you can see on the highest level the order and timings of various events.