Fix --tail panic on undecryptable events by macalinao · Pull Request #208 · 8go/matrix-commander-rs

macalinao · 2026-06-24T09:28:03Z

listen_tail() assumed every fetched timeline event was a Decrypted
variant and called panic!() for anything else (src/listen.rs:684). A
single unable-to-decrypt (UTD) or plaintext event in the tail window
therefore crashes the whole program.

This happens routinely on a verified device that is missing the room key for
some older event (e.g. a megolm session that was never in the key backup):

$ matrix-commander-rs --tail 8 --room '!room:server'
Message: type Text: body "...", ...
thread 'main' panicked at src/listen.rs:684:17:
explicit panic

Handle the non-Decrypted case gracefully instead: print a notice (in text
form, or the raw JSON for --output json), count it toward err_count, and
continue with the next event. --tail now prints what it can and skips what
it cannot decrypt.

listen_tail() assumed every timeline event was a Decrypted variant and called panic!() for anything else. A single unable-to-decrypt (UTD) or plaintext event in the tail window therefore crashed the whole program. Handle the non-Decrypted case gracefully instead: print a notice (in the same style as the messages() RoomEncrypted branch for text output, or the raw JSON for --output json), count it toward err_count, and continue with the next event.

kcexn · 2026-06-24T10:06:41Z

@macalinao Since you're already looking at this. Do you think you could add support for plain text events when tailing? I have a use-case where I'd like to use matrix-commander-rs to administer a Tuwunel homeserver on the host via the built-in (unencrypted) admin room.

Benjamin-Loison · 2026-06-24T19:18:34Z

I do not notice any string typo and the code seems to quickly make sense.

I am testing these changes.

Improve_websites_thanks_to_open_source/issues/3771 would have helped.

Benjamin-Loison · 2026-06-24T19:44:47Z

@macalinao Any reason to use unwrap_or_default instead of unwrap?

Personal notes:

Before this pull request:

cargo run -- --tail

Output:

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.27s
     Running `target/debug/matrix-commander-rs --tail`
error: a value is required for '--tail <TAIL>' but none was supplied

cargo run -- --tail 1

Output:

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.27s
     Running `target/debug/matrix-commander-rs --tail 1`

echo $?

cargo run -- --tail 1 --room '!sNARMdEsFZERaQAJzl:matrix.org'

Output:

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.27s
     Running `target/debug/matrix-commander-rs --tail 1 --room ''\!'sNARMdEsFZERaQAJzl:matrix.org'`
Message: type Text: body "c", room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event id "$2CGM1oUriVNr-RcleAFnKlVpaFhjizdopvrW8236cLM", formatted None,

It seems that I had to start typing on my receiver side for the command to emit and stop.

cargo run -- --tail 20 --room '!sNARMdEsFZERaQAJzl:matrix.org'

Output:

    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.28s
     Running `target/debug/matrix-commander-rs --tail 20 --room ''\!'sNARMdEsFZERaQAJzl:matrix.org'`

thread 'main' (384276) panicked at src/listen.rs:684:17:
explicit panic
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

--room is not necessary to reproduce the issue and the wanted behavior.

With this pull request changes:

cargo run -- --tail 20

Output:

   Compiling matrix-commander v1.0.1 (/home/ubuntu/matrix-commander-rs)
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 25.99s
     Running `target/debug/matrix-commander-rs --tail 20`
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@overclock3000:matrix.org", event_id "$MeBYv1xgfSJ9h1FLFoqRIldjpiNUm1Ahc72ZN4hGpBk", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@overclock3000:matrix.org", event_id "$EVBodDnk_KA65gPOneqdw0Rzw8DN1-2WlBCAMhhdJjE", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event_id "$gC_umVkXT4IrnI2cZtOwDgHRx5BxZ3SyTrlkkMkWm0o", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event_id "$xFzqRlw6MYKNOrprWhNyP2pKC6vY95fdavZ1UCQJLl4", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event_id "$N4opf7pYH_efkTrKx5CWusawzlffsNYg6v4N-L8ohB8", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@overclock3000:matrix.org", event_id "$D23cWkuXZqe8v-_4b2pzWyU5SVF4fHpVfGfJouiZiAc", message could not be decrypted
Message: type Encrypted: room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event_id "$WiADAB8d9-eXSh6QfRPcArc0ARjMKxWmxZ3FFfZkbXU", message could not be decrypted
Message: type Text: body "C", room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event id "$tRFx-UDQlk7cmeJtzeUAbXy303xdTtdrHJwaQtfO-JA", formatted None, 
Message: type Text: body "c", room "!sNARMdEsFZERaQAJzl:matrix.org", sender "@benjamin_loison:matrix.org", event id "$2CGM1oUriVNr-RcleAFnKlVpaFhjizdopvrW8236cLM", formatted None, 
2026-06-24T19:34:41.739310Z ERROR matrix_commander_rs: Error: crate::listen_tail reported Not Implemented Yet
2026-06-24T19:34:41.740971Z ERROR matrix_commander_rs: Encountered 1 error.
Error: NotImplementedYet

Have to check #209 before merging due to:

files#diff-624021025ebdbf037d011a86160f2bd2bb2d97cea072753a5dae9526c580cafcR688-R690

DuckDuckGo search unwrap_or_default.

https://doc.rust-lang.org/std/option/enum.Option.html#method.unwrap_or_default

cargo run -- --tail 16 --output json

Output:

...
{"content":{"body":"From LemnosLife VPS `/var/www/notify.py`: benjamin-loison-framework benjamin_loison -c PERCENT=$(df -h / | tail -n 1 | tr -s   | cut -d   -f5 | sed s/%//g); if [[ $PERCENT -ge 98 ]]; then echo Running out of storage!; fi 0 Running out of storage!","msgtype":"m.text"},"event_id":"$2q40I0EHzlsrWbdnFF3JdjusYeemwKCaPUr-NMOkUG0","origin_server_ts":1782327614122,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":2474039,"membership":"join"}}
{"content":{"body":"a","msgtype":"m.text"},"event_id":"$J-DfDZLUPwn2Cyc5SsO5U_Y0e6B7xeN7aPnKDrK3cz8","origin_server_ts":1782329336128,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":752033,"membership":"join","transaction_id":"9a252dc851034d36ab0ed0762cdc7ffd"}}
{"content":{"body":"b","msgtype":"m.text"},"event_id":"$CyehA32Ye9M2ZZj91Hg_3eLNdFmipmXcAjKKctpJBzQ","origin_server_ts":1782329346528,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":741633,"membership":"join","transaction_id":"20258afcabf845df8b015967f587436d"}}
{"content":{"body":"c","m.mentions":{},"msgtype":"m.text"},"event_id":"$2CGM1oUriVNr-RcleAFnKlVpaFhjizdopvrW8236cLM","origin_server_ts":1782329500725,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@benjamin_loison:matrix.org","type":"m.room.message","unsigned":{"age":587436,"membership":"join"}}
2026-06-24T19:41:28.237789Z ERROR matrix_commander_rs: Error: crate::listen_tail reported Not Implemented Yet
2026-06-24T19:41:28.239469Z ERROR matrix_commander_rs: Encountered 1 error.
Error: NotImplementedYet

Unclear why I have Benjamin-Loison/element-android/issues/65 on my Fairphone 4 LineageOS 23.2 and Linux Mint 22.3 Cinnamon Framework 13, especially as this is not this matrix-commander-rs which sent this encrypted message, but it retrieves it correctly for the first one, but not without --output json.

DuckDuckGo search TimelineEventKind.

cargo run -- --tail 16 --output json --log-level debug

Output:

...
2026-06-24T21:04:32.451561Z DEBUG matrix_commander_rs::listen: rawevent = value is Raw::<ruma_events::enums::AnyTimelineEvent> { json: RawValue({"content":{"body":"From LemnosLife VPS `/var/www/notify.py`: benjamin-loison-framework benjamin_loison -c PERCENT=$(df -h / | tail -n 1 | tr -s   | cut -d   -f5 | sed s/%//g); if [[ $PERCENT -ge 98 ]]; then echo Running out of storage!; fi 0 Running out of storage!","msgtype":"m.text"},"event_id":"$2q40I0EHzlsrWbdnFF3JdjusYeemwKCaPUr-NMOkUG0","origin_server_ts":1782327614122,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":7458252,"membership":"join"}}) }

{"content":{"body":"From LemnosLife VPS `/var/www/notify.py`: benjamin-loison-framework benjamin_loison -c PERCENT=$(df -h / | tail -n 1 | tr -s   | cut -d   -f5 | sed s/%//g); if [[ $PERCENT -ge 98 ]]; then echo Running out of storage!; fi 0 Running out of storage!","msgtype":"m.text"},"event_id":"$2q40I0EHzlsrWbdnFF3JdjusYeemwKCaPUr-NMOkUG0","origin_server_ts":1782327614122,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":7458252,"membership":"join"}}
2026-06-24T21:04:32.451625Z DEBUG matrix_commander_rs::listen: processing message 14 out of 16
2026-06-24T21:04:32.451641Z DEBUG matrix_commander_rs::listen: rawevent = value is Raw::<ruma_events::enums::AnyTimelineEvent> { json: RawValue({"content":{"body":"a","msgtype":"m.text"},"event_id":"$J-DfDZLUPwn2Cyc5SsO5U_Y0e6B7xeN7aPnKDrK3cz8","origin_server_ts":1782329336128,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":5736246,"membership":"join","transaction_id":"9a252dc851034d36ab0ed0762cdc7ffd"}}) }

{"content":{"body":"a","msgtype":"m.text"},"event_id":"$J-DfDZLUPwn2Cyc5SsO5U_Y0e6B7xeN7aPnKDrK3cz8","origin_server_ts":1782329336128,"room_id":"!sNARMdEsFZERaQAJzl:matrix.org","sender":"@overclock3000:matrix.org","type":"m.room.message","unsigned":{"age":5736246,"membership":"join","transaction_id":"9a252dc851034d36ab0ed0762cdc7ffd"}}
...

DuckDuckGo and Google search AnyTimelineEvent.

https://docs.rs/ruma-events/latest/ruma_events/enum.AnyTimelineEvent.html

DuckDuckGo search room chunk matrix sdk.

https://docs.rs/matrix-sdk/0.18.0/matrix_sdk/room/struct.Room.html

https://docs.rs/matrix-sdk/0.18.0/matrix_sdk/room/struct.Messages.html

https://docs.rs/matrix-sdk/0.18.0/matrix_sdk/deserialized_responses/struct.TimelineEvent.html

cargo run -- --tail 16 --output json --log-level debug

Output:

   Compiling matrix-commander v1.0.1 (/home/ubuntu/matrix-commander-rs)
error[E0164]: expected tuple struct or tuple variant, found struct variant `TimelineEventKind::PlainText`
   --> src/listen.rs:684:24
    |
684 |                 if let TimelineEventKind::PlainText(plaintext) = &anytimelineevent.kind {
    |                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ not a tuple struct or tuple variant
    |
help: the struct variant's field is being ignored
    |
684 -                 if let TimelineEventKind::PlainText(plaintext) = &anytimelineevent.kind {
684 +                 if let TimelineEventKind::PlainText { event: _ } = &anytimelineevent.kind {
    |

For more information about this error, try `rustc --explain E0164`.
error: could not compile `matrix-commander` (bin "matrix-commander-rs") due to 1 previous error

Note:

DEBUG matrix_commander_rs::listen: Skipping message from itself because --listen-self is not set.

Benjamin-Loison · 2026-06-24T21:20:35Z

As my tests look concluding, I merge now and you are free to answer my question thank you for the contribution @macalinao!

8go · 2026-07-02T10:40:14Z

Thank you @macalinao. Your PR is appreciated! ❤️

8go · 2026-07-02T10:41:23Z

thank you @Benjamin-Loison for merging 👏 and being so active!

Benjamin-Loison mentioned this pull request Jun 24, 2026

--tail flag is panicking #207

Closed

Benjamin-Loison mentioned this pull request Jun 24, 2026

Add --restore-backup to download room keys from the server-side backup #209

Open

Benjamin-Loison merged commit 6c48a37 into 8go:main Jun 24, 2026
1 check passed

kcexn mentioned this pull request Jun 25, 2026

Fix #207: Add support for PlainText events when tailing. #211

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Fix --tail panic on undecryptable events#208

Fix --tail panic on undecryptable events#208
Benjamin-Loison merged 1 commit into
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macalinao:fix-tail-panic

macalinao commented Jun 24, 2026

Uh oh!

kcexn commented Jun 24, 2026

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Benjamin-Loison commented Jun 24, 2026 •

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macalinao commented Jun 24, 2026

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