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# Description After this pr, nushell is able to raise errors with a backtrace, which should make users easier to debug. To enable the feature, users need to set env variable via `$env.NU_BACKTRACE = 1`. But yeah it might not work perfectly, there are some corner cases which might not be handled. I think it should close #13379 in another way. ### About the change The implementation mostly contained with 2 parts: 1. introduce a new `ChainedError` struct as well as a new `ShellError::ChainedError` variant. If `eval_instruction` returned an error, it converts the error to `ShellError::ChainedError`. `ChainedError` struct is responsable to display errors properly. It needs to handle the following 2 cases: - if we run a function which runs `error make` internally, it needs to display the error itself along with caller span. - if we run a `error make` directly, or some commands directly returns an error, we just want nushell raise an error about `error make`. 2. Attach caller spans to `ListStream` and `ByteStream`, because they are lazy streams, and *only* contains the span that runs it directly(like `^false`, for example), so nushell needs to add all caller spans to the stream. For example: in `def a [] { ^false }; def b [] { a; 33 }; b`, when we run `b`, which runs `a`, which runs `^false`, the `ByteStream` only contains the span of `^false`, we need to make it contains the span of `a`, so nushell is able to get all spans if something bad happened. This behavior is happened after running `Instruction::Call`, if it returns a `ByteStream` and `ListStream`, it will call `push_caller_span` method to attach call spans. # User-Facing Changes It's better to demostrate how it works by examples, given the following definition: ```nushell > $env.NU_BACKTRACE = 1 > def a [x] { if $x == 3 { error make {msg: 'a custom error'}}} > def a_2 [x] { if $x == 3 { ^false } else { $x } } > def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } > def b [--list-stream --external] { if $external == true { # error with non-zero exit code, which is generated from external command. a_2 1; a_2 3; a_2 2 } else if $list_stream == true { # error generated by list-stream a_3 1; a_3 3; a_3 2 } else { # error generated by command directly a 1; a 2; a 3 } } ``` Run `b` directly shows the following error: <details> ```nushell Error: chained_error × oops ╭─[entry #27:1:1] 1 │ b · ┬ · ╰── error happened when running this ╰──── Error: chained_error × oops ╭─[entry #26:10:19] 9 │ # error generated by command directly 10 │ a 1; a 2; a 3 · ┬ · ╰── error happened when running this 11 │ } ╰──── Error: × a custom error ╭─[entry #6:1:26] 1 │ def a [x] { if $x == 3 { error make {msg: 'a custom error'}}} · ─────┬──── · ╰── originates from here ╰──── ``` </details> Run `b --list-stream` shows the following error <details> ```nushell Error: chained_error × oops ╭─[entry #28:1:1] 1 │ b --list-stream · ┬ · ╰── error happened when running this ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #26:7:16] 6 │ # error generated by list-stream 7 │ a_3 1; a_3 3; a_3 2 · ─┬─ · ╰── source value 8 │ } else { ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #23:1:29] 1 │ def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } · ┬ · ╰── source value ╰──── Error: × a custom error inside list stream ╭─[entry #23:1:44] 1 │ def a_3 [x] { if $x == 3 { [1 2 3] | each {error make {msg: 'a custom error inside list stream'} } } } · ─────┬──── · ╰── originates from here ╰──── ``` </details> Run `b --external` shows the following error: <details> ```nushell Error: chained_error × oops ╭─[entry #29:1:1] 1 │ b --external · ┬ · ╰── error happened when running this ╰──── Error: nu:🐚:eval_block_with_input × Eval block failed with pipeline input ╭─[entry #26:4:16] 3 │ # error with non-zero exit code, which is generated from external command. 4 │ a_2 1; a_2 3; a_2 2 · ─┬─ · ╰── source value 5 │ } else if $list_stream == true { ╰──── Error: nu:🐚:non_zero_exit_code × External command had a non-zero exit code ╭─[entry #7:1:29] 1 │ def a_2 [x] { if $x == 3 { ^false } else { $x } } · ──┬── · ╰── exited with code 1 ╰──── ``` </details> It also added a message to guide the usage of NU_BACKTRACE, see the last line in the following example: ```shell ls asdfasd Error: nu:🐚:io::not_found × I/O error ╰─▶ × Entity not found ╭─[entry #17:1:4] 1 │ ls asdfasd · ───┬─── · ╰── Entity not found ╰──── help: The error occurred at '/home/windsoilder/projects/nushell/asdfasd' set the `NU_BACKTRACE=1` environment variable to display a backtrace. ``` # Tests + Formatting Added some tests for the behavior. # After Submitting |
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nu-protocol
The nu-protocol crate holds the definitions of structs/traits that are used throughout Nushell. This gives us one way to expose them to many other crates, as well as make these definitions available to each other, without causing mutually recursive dependencies.