• Daniel Martí's avatar
    text/template: recover panics during function calls · 202e9031
    Daniel Martí authored
    There's precedent in handling panics that happen in functions called
    from the standard library. For example, if a fmt.Formatter
    implementation fails, fmt will absorb the panic into the output text.
    
    Recovering panics is useful, because otherwise one would have to wrap
    some Template.Execute calls with a recover. For example, if there's a
    chance that the callbacks may panic, or if part of the input data is nil
    when it shouldn't be.
    
    In particular, it's a common confusion amongst new Go developers that
    one can call a method on a nil receiver. Expecting text/template to
    error on such a call, they encounter a long and confusing panic if the
    method expects the receiver to be non-nil.
    
    To achieve this, introduce safeCall, which takes care of handling error
    returns as well as recovering panics. Handling panics in the "call"
    function isn't strictly necessary, as that func itself is run via
    evalCall. However, this makes the code more consistent, and can allow
    for better context in panics via the "call" function.
    
    Finally, add some test cases with a mix of funcs, methods, and func
    fields that panic.
    
    Fixes #28242.
    
    Change-Id: Id67be22cc9ebaedeb4b17fa84e677b4b6e09ec67
    Reviewed-on: https://go-review.googlesource.com/c/143097
    Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarRob Pike <r@golang.org>
    202e9031
exec.go 29.1 KB