Upgrade to go 1.20 and add multi-cause error support #121
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Go 1.20 introduces the idea of an error with multiple causes instead of a single chain. This commit updates the errors library to properly encode, decode, and format these error types. For encoding and decoding we use the existing `EncodedLeaf` type and embellish it with a `causes` field. This is done in order to keep the encoding/decoding backwards compatible. `EncodedLeaf` types containing multiple causes when decided by earlier versions will simply see an opaque leaf with a message inside. The reason the `EncodedWrapper` is not used here is because the wrapper already contains a mandatory single `cause` field that we cannot fill with the multi-errors. A new type cannot be used because it would not be decodable by older versions of this library.
support multi-cause errors in go 1.20
Previously, error formatting logic was based on a single linear chain
of causality. Error causes would be printed vertically down the page,
and their interpretation was natural.
This commit adds multi-cause formatting support with two goals in
mind:
1. Preserve output exactly as before for single-cause error chains
2. Format multi-errors in a way that preserves the existing vertical
layout style.
For non-verbose error display (`.Error()`, `%s`, `%v`) there are no
changes implemented here. We rely on the error's own display logic and
typically a multi-cause error will have a message within that has been
constructed from all of its causes during instantiation.
For verbose error display (`%+v`) which relies on object
introspection, whenever we encounter a multi-cause error in the chain,
we mark that subtree as being displayed with markers for the "depth"
of various causes. All child errors of the parent, will be at depth
"1", their child errors will be at depth "2", etc. During display, we
indent the error by its "depth" and add a `└─` symbol to illustrate
the parent/child relationship.
Example:
Printing the error produced by this construction using the format directive `%+v`
```
fmt.Errorf(
"prefix1: %w",
fmt.Errorf(
"prefix2 %w",
goErr.Join(
fmt.Errorf("a%w", fmt.Errorf("b%w", fmt.Errorf("c%w", goErr.New("d")))),
fmt.Errorf("e%w", fmt.Errorf("f%w", fmt.Errorf("g%w", goErr.New("h")))),
)))
```
Produces the following output:
```
prefix1: prefix2: abcd
(1) prefix1
Wraps: (2) prefix2
Wraps: (3) abcd
| efgh
└─ Wraps: (4) efgh
└─ Wraps: (5) fgh
└─ Wraps: (6) gh
└─ Wraps: (7) h
└─ Wraps: (8) abcd
└─ Wraps: (9) bcd
└─ Wraps: (10) cd
└─ Wraps: (11) d
Error types: (1) *fmt.wrapError (2) *fmt.wrapError (3)
*errors.joinError (4) *fmt.wrapError (5) *fmt.wrapError (6)
*fmt.wrapError (7) *errors.errorString (8) *fmt.wrapError (9)
*fmt.wrapError (10) *fmt.wrapError (11) *errors.errorString`,
```
Note the following properties of the output:
* The top-level single cause chain maintains the left-aligned `Wrap`
lines which contain each cause one at a time.
* As soon as we hit the multi-cause errors within the `joinError`
struct (`(3)`), we add new indentation to show that The child errors
of `(3)` are `(4)` and `(8)`
* Subsequent causes of errors after `joinError`, are also indented to
disambiguate the causal chain
* The `Error types` section at the bottom remains the same and the
numbering of the types can be matched to the errors above using the
integers next to the `Wrap` lines.
* No special effort has been made to number the errors in a way that
describes the causal chain or tree. This keeps it easy to match up the
error to its type descriptor.
Previous support for multi-cause encode/decode functionality, did not include support for custom encoder and decoder logic. This commits adds the ability to register encoders and decoders for multi-cause errors to encode custom types unknown to this library.
add formatting for multi-cause errors
This commit introduces a drop-in replacement of the go errors lib `Join` method which constructs a simple multi-cause error object. Some simple unit tests are added and `Join` wrappers are also integrated into the datadriven formatting test. Our existing format code for multi-cause errors is compatible with this new type which allows us to remove the custom formatter from the implementation. The public Join API contains wrappers that automatically attach stacktraces to the join errors. Signed-off-by: Steve Coffman <steve@khanacademy.org>
Add Go 1.20 errors.Join support
This commit modifies the causal detail collection code in `report.go` to recurse through both the single-cause chain and the multi-cause chain if applicable when collecting information for the Sentry report.
Add multi-cause unwrap into Sentry reporting
update README with new public API changes
knz
approved these changes
Aug 23, 2023
knz
reviewed
Aug 23, 2023
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I guess this can change here too.
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This work was done separately on the
go-1.20-upgradebranch and reviewed in:#113
#115
#118
#119
#120
This change is