Constructing String(x::Vector{UInt8}) empties the vector?

data = Vector{UInt8}("hello, world!")
@assert(!isempty(data)) # boom!

is this expected?

I found this issue:, which eventually was resolved by copying data when converting string to a vector. Perhaps, when constructing a string from a vector, it should also copy?


Actually, after reading that thread more thoroughly, Jeff Bezanson suggested (and implemented?) precisely this behaviour: Conversion of String to Vector{UInt8} · Issue #24388 · JuliaLang/julia · GitHub

So I guess this is “by design” because Julia doesn’t have move().

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Still, it’s mind-blowing that String constructor is allowed to do that.


I agree this is surprising, but it is explicitly documented:

help?> String
search: String string StringIndexError Cstring Cwstring bitstring SubString include_string setrounding unsafe_string AbstractString escape_string unescape_string AbstractUnitRange SubstitutionString setprecision AbstractIrrational


  Create a new String object from a byte vector v containing UTF-8 encoded characters. If v is Vector{UInt8} it will be truncated to zero length and future modification of v cannot affect the contents of the resulting string. To avoid
  truncation of Vector{UInt8} data, use String(copy(v)); for other AbstractVector types, String(v) already makes a copy.

I guess it’s slightly out of convention. Proper name should be String!, then there would be no confusion.


If you want a non-destructive string view of a byte array, another option is GitHub - JuliaStrings/StringViews.jl: String-like views of arbitrary Julia byte arrays


The problem is people will read this documentation after their tests fail in a weird way, not before (if they have tests, that is).

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