[pbs-devel] [PATCH proxmox-backup] fix #3921: client: confusing backup reader error

[Gabriel Goller]

On 9/1/23 13:51, Thomas Lamprecht wrote:
> Am 01/09/2023 um 10:02 schrieb Gabriel Goller:
>> When using the catalog shell command, a common error is that user pass
>> "./files.pxar" instead of "files.pxar". This will result in a cryptic error
>> "... value does not match regex pattern ...". Added some context to the
>> error according to suggestions here [1].
> adding error context can be good in general, but the specific case
> mentioned could be also solved explicitly by either stripping ./
> or handling it explicitly. How does it handle multiple consecutive
> slashes in paths? Like "foo///bar"? As that would need similar
> normalizing so, if that works, then we maybe got already some place
> where we can add handling for ./, and otherwise it might make sense
> to start thinking about adding such things.

We return the error above. We have this regex
in place for all file-names:
`PROXMOX_SAFE_ID_REGEX_STR { () => { r"(?:[A-Za-z0-9_][A-Za-z0-9._\-]*)" 
}; }`

> As when multiple users run into some issue it might be warranted
> to check if them "holding it wrong" should be actually a valid way
> to hold it.
I don't think so to be honest, because AFAIK we don't support directories
in snapshots (?) so it doesn't make sense to pass "./test.pxar".

Stripping is also wrong, because the . (dot) would be an accepted character
in the file-name and thus we cannot remove it. Though we could remove every
prohibited character (the / in this case) and the characters around
(the . in our example)?

>> [1]: https://bugzilla.proxmox.com/show_bug.cgi?id=3921
>>
>> Signed-off-by: Gabriel Goller <g.goller at proxmox.com>
>> ---
>>   pbs-client/src/backup_reader.rs | 5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/pbs-client/src/backup_reader.rs b/pbs-client/src/backup_reader.rs
>> index 2cd4dc27..138e836a 100644
>> --- a/pbs-client/src/backup_reader.rs
>> +++ b/pbs-client/src/backup_reader.rs
>> @@ -98,7 +98,10 @@ impl BackupReader {
>>       pub async fn download<W: Write + Send>(&self, file_name: &str, output: W) -> Result<(), Error> {
>>           let path = "download";
>>           let param = json!({ "file-name": file_name });
>> -        self.h2.download(path, Some(param), output).await
>> +        self.h2
>> +            .download(path, Some(param), output)
>> +            .await
>> +            .map_err(|err| format_err!("http2 file download '{}' failed: \n{}", file_name, err))
> please use captured identifiers for new format!/format_err! et al.
> calls, e.g., here:
>
> .map_err(|err| format_err!("http2 file download '{file_name}' failed - {err}"))
>
> We also normally do not use a newline to separate prefix from actual
> error, or would there be a good reason to deviate from the norm here?
Yes, because the `err` is a multi-line string here. On the api we have a 
`Vec` of errors and return it as a string using `\n`
as a delimiter.
>>       }
>>   
>>       /// Execute a special GET request and send output to a writer