ffx_command_error/
error.rs

1// Copyright 2023 The Fuchsia Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5use errors::FfxError;
6use traceable_error_derive::TraceableError;
7
8/// Represents a recoverable error. Intended to be embedded in `Error`.
9#[derive(thiserror::Error, Debug)]
10#[error("non-fatal error encountered")]
11pub struct NonFatalError(#[source] pub anyhow::Error);
12
13/// A top level error type for ffx tool results
14#[derive(thiserror::Error, Debug, TraceableError)]
15pub enum Error {
16    /// An error that qualifies as a bugcheck
17    Unexpected(#[source] anyhow::Error),
18    /// A known kind of error that can be reported usefully to the user
19    User(#[source] anyhow::Error),
20    /// An early-exit that should result in outputting help to the user (like [`argh::EarlyExit`]),
21    /// but is not itself an error in any meaningful sense.
22    Help {
23        /// The command name (argv[0..]) that should be used in supplemental help output
24        command: Vec<String>,
25        /// The text to output to the user
26        output: String,
27        /// The exit status
28        code: i32,
29    },
30    /// An error from general I/O. Meant mostly to handle things like write!() and such, but also
31    /// for potential issues with piping outputs of other commands into ffx. This isn't something
32    /// that's exactly common, but is a possibility.
33    #[trace(opaque)]
34    IoError(#[from] std::io::Error),
35    /// Something failed before ffx's configuration could be loaded (like an
36    /// invalid argument, a failure to read an env config file, etc).
37    ///
38    /// Errors of this type should include any information the user might need
39    /// to recover from the issue, because it will not advise the user to look
40    /// in the log files or anything like that.
41    Config(#[source] anyhow::Error),
42    /// Exit with a specific error code but no output
43    ExitWithCode(i32),
44}
45
46impl Error {
47    /// Attempts to downcast this error into something non-fatal, returning `Ok(e)`
48    /// if able to downcast to something non-fatal, else returning the original error.
49    pub fn downcast_non_fatal(self) -> Result<anyhow::Error, Self> {
50        fn try_downcast(err: anyhow::Error) -> Result<anyhow::Error, anyhow::Error> {
51            match err.downcast::<NonFatalError>() {
52                Ok(NonFatalError(e)) => Ok(e),
53                Err(e) => Err(e),
54            }
55        }
56
57        match self {
58            Self::Help { .. } | Self::ExitWithCode(_) | Self::IoError(_) => Err(self),
59            Self::User(e) => try_downcast(e).map_err(Self::User),
60            Self::Unexpected(e) => try_downcast(e).map_err(Self::Unexpected),
61            Self::Config(e) => try_downcast(e).map_err(Self::Config),
62        }
63    }
64
65    /// Attempts to get the original `anyhow::Error` source (this is useful for chaining context
66    /// errors). If successful, returns `Ok(e)` with the error source, but if there's no error
67    /// source that can be returned, returns `self`.
68    pub fn source(self) -> Result<anyhow::Error, Self> {
69        match self {
70            Self::User(e) | Self::Unexpected(e) | Self::Config(e) => Ok(e),
71            Self::Help { .. } | Self::ExitWithCode(_) | Self::IoError(_) => Err(self),
72        }
73    }
74}
75
76/// Writes a detailed description of an anyhow error to the formatter
77fn write_detailed(f: &mut std::fmt::Formatter<'_>, error: &anyhow::Error) -> std::fmt::Result {
78    write!(f, "Error: {}", error)?;
79    for (i, e) in error.chain().skip(1).enumerate() {
80        write!(f, "\n  {: >3}.  {}", i + 1, e)?;
81    }
82    Ok(())
83}
84
85fn write_display(f: &mut std::fmt::Formatter<'_>, error: &anyhow::Error) -> std::fmt::Result {
86    write!(f, "{error}")?;
87    let mut previous_error = error.to_string();
88    for e in error.chain().skip(1) {
89        // This is a total hack. When errors are chained together through various thiserror
90        // wrappers, what can happen is the error will use this display function to make itself
91        // into a string, and the display function will show duplicates of the context chain.
92        //
93        // If, for example, we have something like `ffx_bail!` which returns an error, and it is
94        // encapsulated into a `thiserror` enum, and then later wrapped into a
95        // `ffx_command::Error::User`, we will have a context chain with the same error multiple
96        // times in a row. For example, say we have something like:
97        //
98        // ```
99        // let err = ffx_error!(anyhow!("this thing broke"));
100        // let err2 = LogError::FfxError(err);
101        // let err3 = ffx_command::Error::User(err2);
102        // eprintln!("{err3}");
103        // ```
104        //
105        // This will print: "this thing broke: this thing broke"
106        //
107        // This check will prevent that from happening without removing the context chain.
108        let err_string = format!("{}", e);
109        // There have been issues with empty strings in the past when formatting errors. Make
110        // sure to explicitly show that an empty string is in one of the errors so that it can
111        // be caught. This sort of thing used to happen with certain SSH errors.
112        let err_string = if err_string.is_empty() { "\"\"".to_owned() } else { err_string };
113        if err_string == previous_error {
114            continue;
115        }
116        write!(f, ": {}", err_string)?;
117        previous_error = err_string;
118    }
119    Ok(())
120}
121
122// LINT.IfChange
123const BUG_LINE: &str = "BUG: An internal command error occurred.";
124// LINT.ThenChange(//src/testing/end_to_end/honeydew/honeydew/affordances/session/session_using_ffx.py)
125impl std::fmt::Display for Error {
126    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
127        match self {
128            Self::Unexpected(error) => {
129                writeln!(f, "{BUG_LINE}")?;
130                write_detailed(f, error)
131            }
132            Self::User(error) | Self::Config(error) => write_display(f, error),
133            Self::Help { output, .. } => write!(f, "{output}"),
134            Self::ExitWithCode(code) => write!(f, "Exiting with code {code}"),
135            Self::IoError(e) => write!(f, "I/O error: {e}"),
136        }
137    }
138}
139
140impl From<anyhow::Error> for Error {
141    fn from(error: anyhow::Error) -> Self {
142        // If it's already an Error, just return it
143        match error.downcast::<Self>() {
144            Ok(this) => this,
145            // this is just a compatibility shim to extract information out of the way
146            // we've traditionally divided user and unexpected errors.
147            Err(error) => match error.downcast::<FfxError>() {
148                Ok(err) => Self::User(err.into()),
149                Err(err) => Self::Unexpected(err),
150            },
151        }
152    }
153}
154
155impl From<FfxError> for Error {
156    fn from(error: FfxError) -> Self {
157        Error::User(error.into())
158    }
159}
160
161impl Error {
162    /// Map an argh early exit to our kind of error
163    pub fn from_early_exit(command: &[impl AsRef<str>], early_exit: argh::EarlyExit) -> Self {
164        let command = Vec::from_iter(command.iter().map(|s| s.as_ref().to_owned()));
165        let output = early_exit.output;
166        // if argh's early_exit status is Ok() that means it's printing help because
167        // of a `--help` argument or `help` as a subcommand was passed. Otherwise
168        // it's just an error parsing the arguments. So only map `status: Ok(())`
169        // as help output.
170        match early_exit.status {
171            Ok(_) => Error::Help { command, output, code: 0 },
172            Err(_) => Error::Config(anyhow::anyhow!("{}", output)),
173        }
174    }
175
176    /// Get the exit code this error should correspond to if it bubbles up to `main()`
177    pub fn exit_code(&self) -> i32 {
178        match self {
179            Error::User(err) => {
180                if let Some(FfxError::Error(_, code)) = err.downcast_ref() {
181                    *code
182                } else {
183                    1
184                }
185            }
186            Error::Help { code, .. } => *code,
187            Error::ExitWithCode(code) => *code,
188            _ => 1,
189        }
190    }
191}
192
193/// A convenience Result type
194pub type Result<T, E = crate::Error> = core::result::Result<T, E>;
195
196#[cfg(test)]
197mod tests {
198    use super::*;
199    use crate::tests::*;
200    use anyhow::anyhow;
201    use assert_matches::assert_matches;
202    use errors::{IntoExitCode, ffx_error, ffx_error_with_code};
203    use std::io::{Cursor, Write};
204
205    #[test]
206    fn test_write_result_ffx_error() {
207        let err = Error::from(ffx_error!(FFX_STR));
208        let mut cursor = Cursor::new(Vec::new());
209
210        assert_matches!(write!(&mut cursor, "{err}"), Ok(_));
211
212        assert!(String::from_utf8(cursor.into_inner()).unwrap().contains(FFX_STR));
213    }
214
215    #[test]
216    fn into_error_from_arbitrary_is_unexpected() {
217        let err = anyhow!(ERR_STR);
218        assert_matches!(
219            Error::from(err),
220            Error::Unexpected(_),
221            "an arbitrary anyhow error should convert to an 'unexpected' bug check error"
222        );
223    }
224
225    #[test]
226    fn into_error_from_ffx_error_is_user_error() {
227        let err = FfxError::Error(anyhow!(FFX_STR), 1);
228        assert_matches!(
229            Error::from(err),
230            Error::User(_),
231            "an arbitrary anyhow error should convert to a 'user' error"
232        );
233    }
234
235    #[test]
236    fn into_error_from_contextualized_ffx_error_prints_original_error() {
237        let err = Error::from(anyhow::anyhow!(errors::ffx_error!(FFX_STR)).context("boom"));
238        assert_eq!(
239            &format!("{err}"),
240            FFX_STR,
241            "an anyhow error with context should print the original error, not the context, when stringified."
242        );
243    }
244
245    #[test]
246    fn test_write_result_arbitrary_error() {
247        let err = Error::from(anyhow!(ERR_STR));
248        let mut cursor = Cursor::new(Vec::new());
249
250        assert_matches!(write!(&mut cursor, "{err}"), Ok(_));
251
252        let err_str = String::from_utf8(cursor.into_inner()).unwrap();
253        assert!(err_str.contains(BUG_LINE));
254        assert!(err_str.contains(ERR_STR));
255    }
256
257    #[test]
258    fn test_result_ext_exit_code_ffx_error() {
259        let err = Result::<()>::Err(Error::from(ffx_error_with_code!(42, FFX_STR)));
260        assert_eq!(err.exit_code(), 42);
261    }
262
263    #[test]
264    fn test_from_ok_early_exit() {
265        let command = ["testing", "--help"];
266        let output = "stuff!".to_owned();
267        let status = Ok(());
268        let code = 0;
269
270        let early_exit = argh::EarlyExit { output: output.clone(), status };
271        let err = Error::from_early_exit(&command, early_exit);
272        assert_eq!(err.exit_code(), code);
273        assert_matches!(err, Error::Help { command: error_command, output: error_output, code: error_code } if error_command == command && error_output == output && error_code == code);
274    }
275
276    #[test]
277    fn test_from_error_early_exit() {
278        let command = ["testing", "bad", "command"];
279        let output = "stuff!".to_owned();
280        let status = Err(());
281        let code = 1;
282
283        let early_exit = argh::EarlyExit { output: output.clone(), status };
284        let err = Error::from_early_exit(&command, early_exit);
285        assert_eq!(err.exit_code(), code);
286        assert_matches!(err, Error::Config(err) if format!("{err}") == output);
287    }
288
289    #[test]
290    fn test_downcast_recasts_types() {
291        let err = Error::User(anyhow!("boom"));
292        assert_matches!(err.downcast_non_fatal(), Err(Error::User(_)));
293
294        let err = Error::Unexpected(anyhow!("boom"));
295        assert_matches!(err.downcast_non_fatal(), Err(Error::Unexpected(_)));
296
297        let err = Error::Config(anyhow!("boom"));
298        assert_matches!(err.downcast_non_fatal(), Err(Error::Config(_)));
299
300        let err =
301            Error::Help { command: vec!["foobar".to_owned()], output: "blorp".to_owned(), code: 1 };
302        assert_matches!(err.downcast_non_fatal(), Err(Error::Help { .. }));
303
304        let err = Error::ExitWithCode(2);
305        assert_matches!(err.downcast_non_fatal(), Err(Error::ExitWithCode(2)));
306    }
307
308    #[test]
309    fn test_downcast_non_fatal_recovers_non_fatal_error() {
310        static ERR_STR: &'static str = "Oh look it's non fatal";
311        let constructors = vec![Error::User, Error::Unexpected, Error::Config];
312        for c in constructors.into_iter() {
313            let err = c(NonFatalError(anyhow!(ERR_STR)).into());
314            let res = err.downcast_non_fatal().expect("expected non-fatal downcast");
315            assert_eq!(res.to_string(), ERR_STR.to_owned());
316        }
317    }
318
319    #[test]
320    fn test_error_source() {
321        static ERR_STR: &'static str = "some nonsense";
322        let constructors = vec![Error::User, Error::Unexpected, Error::Config];
323        for cons in constructors.into_iter() {
324            let err = cons(anyhow!(ERR_STR));
325            let res = err.source();
326            assert!(res.is_ok());
327            assert_eq!(res.unwrap().to_string(), ERR_STR.to_owned());
328        }
329    }
330
331    #[test]
332    fn test_error_source_flatten_no_context() {
333        assert_eq!("Some Operation", Error::User(anyhow!("Some Operation")).to_string());
334    }
335
336    // The order of context's is "in-side-out", the root-most error is
337    // created first, and then the context() is attached on all of the
338    // returned values, so they are created in the opposite order that they
339    // are displayed.
340
341    #[test]
342    fn test_error_source_flatten_one_context() {
343        let expected = "Some Other Operation: some failure";
344        let error = anyhow!("some failure");
345        let error = error.context("Some Other Operation");
346        assert_eq!(expected, Error::User(error).to_string());
347    }
348
349    #[test]
350    fn test_error_source_flatten_two_contexts() {
351        let expected = "Some Operation: some context: some failure";
352        let error = anyhow!("some failure");
353        let error = error.context("some context");
354        let error = error.context("Some Operation");
355        assert_eq!(expected, Error::User(error).to_string());
356    }
357
358    #[test]
359    fn test_error_source_flatten_three_contexts() {
360        let expected = "Some Operation: some context: more context: some failure";
361        let error = anyhow!("some failure")
362            .context("more context")
363            .context("some context")
364            .context("Some Operation");
365        assert_eq!(expected, Error::User(error).to_string());
366    }
367
368    #[test]
369    fn test_error_doesnt_duplicate_when_rewrapped() {
370        #[derive(thiserror::Error, Debug)]
371        enum NonsenseErr {
372            #[error(transparent)]
373            Error(#[from] FfxError),
374        }
375        let expected = "This thing broke!";
376        let error = ffx_error!(anyhow!(expected));
377        let error: NonsenseErr = error.into();
378        let error = Error::User(error.into());
379        assert_eq!(
380            error.to_string(),
381            expected.to_owned(),
382            "There should be no duplication from re-wrapping errors"
383        );
384    }
385
386    #[test]
387    fn test_non_fatal_error_formatting() {
388        let inner = anyhow!("inner error");
389        let non_fatal = NonFatalError(inner);
390        let err = Error::User(anyhow!(non_fatal));
391        assert_eq!(format!("{}", err), "non-fatal error encountered: inner error");
392    }
393}
ffx_command_error/error.rs

ffx_command_error/
error.rs
