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91 lines
3.4 KiB
Go
91 lines
3.4 KiB
Go
// Package merry provides enriched golang errors, with stacktraces
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//
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// merry creates errors with stacktraces, and can augment those errors with additional
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// information.
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//
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// When you create a new merry error, or wrap an existing error in a merry error, merry attaches
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// a stacktrace to the error:
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//
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// err := merry.New("an error occurred")
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//
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// err has a stacktrace attached. Alternately, you can wrap existing errors. merry will
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// attach a stacktrace at the point of wrapping:
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//
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// _, err := ioutil.ReadAll(r)
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// if err != nil {
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// return merry.Wrap(err)
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// }
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//
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// Capturing the stack can be globally disabled with `SetStackCaptureEnabled(false)`. Wrapping
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// is idempotent: Wrap will only attach a stacktrace if the error doesn't already have one.
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//
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// Wrap() is the simplest way to attach a stacktrace to an error, but other functions can be
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// used instead, with both add a stacktrace, and augment or modify the error. For example,
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// Prepend() modifies the error's message (and also attaches a stacktrace):
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//
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// _, err := ioutil.ReadAll(r)
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// if err != nil {
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// return merry.Prepend(err, "reading from conn failed")
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// // err.Error() would read something like "reading from conn failed: timeout"
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// }
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//
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// See the other package functions for other ways to augment or modify errors, such as Append,
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// WithUserMessage, WithHTTPCode, WithValue, etc. These functions all return a merry.Error interface, which
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// has methods which mirror the package level functions, to allow simple chaining:
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//
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// return merry.New("object not found").WithHTTPCode(404)
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//
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// Here
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//
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// Wrap will not take a new stacktrace if an error already has one attached. Here will create
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// a new error which replaces the stacktrace with a new one:
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//
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// var ErrOverflow = merry.New("overflowed")
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//
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// func Read() error {
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// // ...
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// return merry.Here(ErrOverflow)
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// }
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//
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// Is
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//
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// The go idiom of exporting package-level error variables for comparison to errors returned
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// by the package is broken by merry. For example:
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//
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// _, err := io.ReadAll(r)
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// if err == io.EOF {
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// // ...
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// }
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//
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// If the error returned was a merry error, the equality comparison would always fail, because merry
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// augments errors by wrapping them in layers. To compensate for this, merry has the Is() function.
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//
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// if merry.Is(err, io.EOF) {
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//
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// Is() will unwrap the err and compare each layer to the second argument.
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//
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// Cause
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//
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// You can add a cause to an error:
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//
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// if err == io.EOF {
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// err = merry.New("reading failed"), err)
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// fmt.Println(err.Error()) // reading failed: EOF
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// }
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//
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// Cause(error) will return the cause of the argument. RootCause(error) returns the innermost cause.
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// Is(err1, err2) is cause aware, and will return true if err2 is a cause (anywhere in the causal change)
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// of err1.
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//
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// Formatting and printing
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//
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// To obtain an error's stacktrace, call Stack(). To get other information about the site
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// of the error, or print the error's stacktrace, see Location(), SourceLine(), Stacktrace(), and Details().
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//
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// merry errors also implement the fmt.Formatter interface. errors support the following fmt flags:
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//
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// %+v print the equivalent of Details(err), which includes the user message, full stacktrace,
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// and recursively prints the details of the cause chain.
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//
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package merry
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