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, IntoExitCode};
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        // We check for containment using `.contains()` (rather than exact equality or
109        // ends_with) to robustly handle cases where a wrapper's message includes its
110        // source's message (which is common with `#[error("...: {0}")]`).
111        let err_string = format!("{}", e);
112        // There have been issues with empty strings in the past when formatting errors. Make
113        // sure to explicitly show that an empty string is in one of the errors so that it can
114        // be caught. This sort of thing used to happen with certain SSH errors.
115        let err_string = if err_string.is_empty() { "\"\"".to_owned() } else { err_string };
116        if previous_error.contains(&err_string) {
117            continue;
118        }
119        write!(f, ": {}", err_string)?;
120        previous_error = err_string;
121    }
122    Ok(())
123}
124
125// LINT.IfChange
126const BUG_LINE: &str = "BUG: An internal command error occurred.";
127// LINT.ThenChange(//src/testing/end_to_end/honeydew/honeydew/affordances/session/session_using_ffx.py)
128impl std::fmt::Display for Error {
129    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
130        match self {
131            Self::Unexpected(error) => {
132                writeln!(f, "{BUG_LINE}")?;
133                write_detailed(f, error)
134            }
135            Self::User(error) | Self::Config(error) => write_display(f, error),
136            Self::Help { output, .. } => write!(f, "{output}"),
137            Self::ExitWithCode(code) => write!(f, "Exiting with code {code}"),
138            Self::IoError(e) => write!(f, "I/O error: {e}"),
139        }
140    }
141}
142
143impl From<anyhow::Error> for Error {
144    fn from(error: anyhow::Error) -> Self {
145        // If it's already an Error, just return it
146        match error.downcast::<Self>() {
147            Ok(this) => this,
148            // this is just a compatibility shim to extract information out of the way
149            // we've traditionally divided user and unexpected errors.
150            Err(error) => match error.downcast::<FfxError>() {
151                Ok(err) => {
152                    Self::User(anyhow::Error::from(traceable_error::TraceableBox::from(err)))
153                }
154                Err(err) => Self::Unexpected(err),
155            },
156        }
157    }
158}
159
160impl From<FfxError> for Error {
161    fn from(error: FfxError) -> Self {
162        Error::User(anyhow::Error::from(traceable_error::TraceableBox::from(error)))
163    }
164}
165
166impl Error {
167    /// Map an argh early exit to our kind of error
168    pub fn from_early_exit(command: &[impl AsRef<str>], early_exit: argh::EarlyExit) -> Self {
169        let command = Vec::from_iter(command.iter().map(|s| s.as_ref().to_owned()));
170        let output = early_exit.output;
171        // if argh's early_exit status is Ok() that means it's printing help because
172        // of a `--help` argument or `help` as a subcommand was passed. Otherwise
173        // it's just an error parsing the arguments. So only map `status: Ok(())`
174        // as help output.
175        match early_exit.status {
176            Ok(_) => Error::Help { command, output, code: 0 },
177            Err(_) => Error::Config(anyhow::anyhow!("{}", output)),
178        }
179    }
180
181    /// Get the exit code this error should correspond to if it bubbles up to `main()`
182    pub fn exit_code(&self) -> i32 {
183        match self {
184            Error::User(err) => err.exit_code(),
185            Error::Help { code, .. } => *code,
186            Error::ExitWithCode(code) => *code,
187            _ => 1,
188        }
189    }
190}
191
192/// A convenience Result type
193pub type Result<T, E = crate::Error> = core::result::Result<T, E>;
194
195#[cfg(test)]
196mod tests {
197    use super::*;
198    use crate::tests::*;
199    use anyhow::anyhow;
200    use assert_matches::assert_matches;
201    use errors::{IntoExitCode, ffx_error, ffx_error_with_code};
202    use std::io::{Cursor, Write};
203
204    #[test]
205    fn test_write_result_ffx_error() {
206        let err = Error::from(ffx_error!(FFX_STR));
207        let mut cursor = Cursor::new(Vec::new());
208
209        assert_matches!(write!(&mut cursor, "{err}"), Ok(_));
210
211        assert!(String::from_utf8(cursor.into_inner()).unwrap().contains(FFX_STR));
212    }
213
214    #[test]
215    fn into_error_from_arbitrary_is_unexpected() {
216        let err = anyhow!(ERR_STR);
217        assert_matches!(
218            Error::from(err),
219            Error::Unexpected(_),
220            "an arbitrary anyhow error should convert to an 'unexpected' bug check error"
221        );
222    }
223
224    #[test]
225    fn into_error_from_ffx_error_is_user_error() {
226        let err = FfxError::Error(anyhow!(FFX_STR), 1);
227        assert_matches!(
228            Error::from(err),
229            Error::User(_),
230            "an arbitrary anyhow error should convert to a 'user' error"
231        );
232    }
233
234    #[test]
235    fn into_error_from_contextualized_ffx_error_prints_original_error() {
236        let err = Error::from(anyhow::anyhow!(errors::ffx_error!(FFX_STR)).context("boom"));
237        assert_eq!(
238            &format!("{err}"),
239            FFX_STR,
240            "an anyhow error with context should print the original error, not the context, when stringified."
241        );
242    }
243
244    #[test]
245    fn test_write_result_arbitrary_error() {
246        let err = Error::from(anyhow!(ERR_STR));
247        let mut cursor = Cursor::new(Vec::new());
248
249        assert_matches!(write!(&mut cursor, "{err}"), Ok(_));
250
251        let err_str = String::from_utf8(cursor.into_inner()).unwrap();
252        assert!(err_str.contains(BUG_LINE));
253        assert!(err_str.contains(ERR_STR));
254    }
255
256    #[test]
257    fn test_result_ext_exit_code_ffx_error() {
258        let err = Result::<()>::Err(Error::from(ffx_error_with_code!(42, FFX_STR)));
259        assert_eq!(err.exit_code(), 42);
260    }
261
262    #[test]
263    fn test_from_ok_early_exit() {
264        let command = ["testing", "--help"];
265        let output = "stuff!".to_owned();
266        let status = Ok(());
267        let code = 0;
268
269        let early_exit = argh::EarlyExit { output: output.clone(), status };
270        let err = Error::from_early_exit(&command, early_exit);
271        assert_eq!(err.exit_code(), code);
272        assert_matches!(err, Error::Help { command: error_command, output: error_output, code: error_code } if error_command == command && error_output == output && error_code == code);
273    }
274
275    #[test]
276    fn test_from_error_early_exit() {
277        let command = ["testing", "bad", "command"];
278        let output = "stuff!".to_owned();
279        let status = Err(());
280        let code = 1;
281
282        let early_exit = argh::EarlyExit { output: output.clone(), status };
283        let err = Error::from_early_exit(&command, early_exit);
284        assert_eq!(err.exit_code(), code);
285        assert_matches!(err, Error::Config(err) if format!("{err}") == output);
286    }
287
288    #[test]
289    fn test_downcast_recasts_types() {
290        let err = Error::User(anyhow!("boom"));
291        assert_matches!(err.downcast_non_fatal(), Err(Error::User(_)));
292
293        let err = Error::Unexpected(anyhow!("boom"));
294        assert_matches!(err.downcast_non_fatal(), Err(Error::Unexpected(_)));
295
296        let err = Error::Config(anyhow!("boom"));
297        assert_matches!(err.downcast_non_fatal(), Err(Error::Config(_)));
298
299        let err =
300            Error::Help { command: vec!["foobar".to_owned()], output: "blorp".to_owned(), code: 1 };
301        assert_matches!(err.downcast_non_fatal(), Err(Error::Help { .. }));
302
303        let err = Error::ExitWithCode(2);
304        assert_matches!(err.downcast_non_fatal(), Err(Error::ExitWithCode(2)));
305    }
306
307    #[test]
308    fn test_downcast_non_fatal_recovers_non_fatal_error() {
309        static ERR_STR: &'static str = "Oh look it's non fatal";
310        let constructors = vec![Error::User, Error::Unexpected, Error::Config];
311        for c in constructors.into_iter() {
312            let err = c(NonFatalError(anyhow!(ERR_STR)).into());
313            let res = err.downcast_non_fatal().expect("expected non-fatal downcast");
314            assert_eq!(res.to_string(), ERR_STR.to_owned());
315        }
316    }
317
318    #[test]
319    fn test_error_source() {
320        static ERR_STR: &'static str = "some nonsense";
321        let constructors = vec![Error::User, Error::Unexpected, Error::Config];
322        for cons in constructors.into_iter() {
323            let err = cons(anyhow!(ERR_STR));
324            let res = err.source();
325            assert!(res.is_ok());
326            assert_eq!(res.unwrap().to_string(), ERR_STR.to_owned());
327        }
328    }
329
330    #[test]
331    fn test_error_source_flatten_no_context() {
332        assert_eq!("Some Operation", Error::User(anyhow!("Some Operation")).to_string());
333    }
334
335    // The order of context's is "in-side-out", the root-most error is
336    // created first, and then the context() is attached on all of the
337    // returned values, so they are created in the opposite order that they
338    // are displayed.
339
340    #[test]
341    fn test_error_source_flatten_one_context() {
342        let expected = "Some Other Operation: some failure";
343        let error = anyhow!("some failure");
344        let error = error.context("Some Other Operation");
345        assert_eq!(expected, Error::User(error).to_string());
346    }
347
348    #[test]
349    fn test_error_source_flatten_two_contexts() {
350        let expected = "Some Operation: some context: some failure";
351        let error = anyhow!("some failure");
352        let error = error.context("some context");
353        let error = error.context("Some Operation");
354        assert_eq!(expected, Error::User(error).to_string());
355    }
356
357    #[test]
358    fn test_error_source_flatten_three_contexts() {
359        let expected = "Some Operation: some context: more context: some failure";
360        let error = anyhow!("some failure")
361            .context("more context")
362            .context("some context")
363            .context("Some Operation");
364        assert_eq!(expected, Error::User(error).to_string());
365    }
366
367    #[test]
368    fn test_error_doesnt_duplicate_when_rewrapped() {
369        #[derive(thiserror::Error, Debug)]
370        enum NonsenseErr {
371            #[error(transparent)]
372            Error(#[from] FfxError),
373        }
374        let expected = "This thing broke!";
375        let error = ffx_error!(anyhow!(expected));
376        let error: NonsenseErr = error.into();
377        let error = Error::User(error.into());
378        assert_eq!(
379            error.to_string(),
380            expected.to_owned(),
381            "There should be no duplication from re-wrapping errors"
382        );
383    }
384
385    #[test]
386    fn test_non_fatal_error_formatting() {
387        let inner = anyhow!("inner error");
388        let non_fatal = NonFatalError(inner);
389        let err = Error::User(anyhow!(non_fatal));
390        assert_eq!(format!("{}", err), "non-fatal error encountered: inner error");
391    }
392
393    #[test]
394    fn test_error_doesnt_duplicate_alternating() {
395        #[derive(thiserror::Error, Debug)]
396        #[error("Prefix: {0}")]
397        struct OuterError(#[source] anyhow::Error);
398
399        #[derive(thiserror::Error, Debug)]
400        #[error("NonFatal")]
401        struct NonFatal(#[source] anyhow::Error);
402
403        #[derive(thiserror::Error, Debug)]
404        #[error("TargetNotFound")]
405        struct TargetNotFound;
406
407        let leaf = TargetNotFound;
408        let non_fatal = NonFatal(anyhow::Error::new(leaf));
409        let fho_err = Error::User(anyhow::Error::new(non_fatal));
410        let outer = OuterError(anyhow::Error::new(fho_err));
411        let top = Error::User(anyhow::Error::new(outer));
412
413        let formatted = top.to_string();
414        assert_eq!(formatted, "Prefix: NonFatal: TargetNotFound");
415    }
416}
ffx_command_error/error.rs

ffx_command_error/
error.rs
