# Calling a macro in a function with \`eval\` fails on nightly

**URL:** <https://discourse.julialang.org/t/calling-a-macro-in-a-function-with-eval-fails-on-nightly/132168>\
**Category:** General Usage\
**Created:** [September 8, 2025, 9:44am UTC](https://discourse.julialang.org/t/calling-a-macro-in-a-function-with-eval-fails-on-nightly/132168 "2025-09-08T09:44:30Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![danielw2904](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielw2904/32/10890_2.png) [@danielw2904](https://discourse.julialang.org/u/danielw2904)\
**Post date:** [September 8, 2025, 9:44am UTC](https://discourse.julialang.org/t/calling-a-macro-in-a-function-with-eval-fails-on-nightly/132168/1 "2025-09-08T09:44:30Z")

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Hello,

I maintain the package [JSONLines.jl](https://github.com/dwinkler1/JSONLines.jl) package which has some syntactic sugar to define a `StructType` to read only specific columns. This fails on the Julia nightly with the following error:

```julia-auto
readcols: Error During Test at /Users/runner/work/JSONLines.jl/JSONLines.jl/test/runtests.jl:55
  Got exception outside of a @test
  MethodError: no method matching JSONLines.var"##jsonlwebsite.jsonl#140"(::String)
  The type `JSONLines.var"##jsonlwebsite.jsonl#140"` exists, but no method is defined for this combination of argument types when trying to construct it.
  Closest candidates are:
    JSONLines.var"##jsonlwebsite.jsonl#140"() (method too new to be called from this world context.)
     @ JSONLines ~/work/JSONLines.jl/JSONLines.jl/src/sugar.jl:13

```

> **Full Stacktrace**
>
> ```julia-auto
> readcols: Error During Test at /Users/runner/work/JSONLines.jl/JSONLines.jl/test/runtests.jl:55
> Got exception outside of a @test
> MethodError: no method matching JSONLines.var"##jsonlwebsite.jsonl#140"(::String)
> The type `JSONLines.var"##jsonlwebsite.jsonl#140"` exists, but no method is defined for this combination of argument types when trying to construct it.
> Closest candidates are:
> JSONLines.var"##jsonlwebsite.jsonl#140"() (method too new to be called from this world context.)
> @ JSONLines ~/work/JSONLines.jl/JSONLines.jl/src/sugar.jl:13
> Stacktrace:
> [1] construct
> @ ~/.julia/packages/StructTypes/PaLwj/src/StructTypes.jl:915 [inlined]
> [2] read(::StructTypes.UnorderedStruct, buf::SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}, pos::Int64, len::Int64, b::UInt8, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"}; ignore_extra_fields::Bool, kw::@Kwargs{})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:652
> [3] read(::StructTypes.UnorderedStruct, buf::SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}, pos::Int64, len::Int64, b::UInt8, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:568
> [4] parse(str::JSON3.VectorString{SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"}; jsonlines::Bool, kw::@Kwargs{})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:40
> [5] kwcall(::@NamedTuple{jsonlines::Bool}, ::typeof(JSON3.parse), str::JSON3.VectorString{SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:32
> [6] read(str::JSON3.VectorString{SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"}; jsonlines::Bool, kw::@Kwargs{})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:46
> [7] read(str::JSON3.VectorString{SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:45
> [8] read(bytes::SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"}; kw::@Kwargs{})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:14
> [9] read(bytes::SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}, ::Type{JSONLines.var"##jsonlwebsite.jsonl#140"})
> @ JSON3 ~/.julia/packages/JSON3/rT1w2/src/structs.jl:14
> [10] parserow(row::SubArray{UInt8, 1, Vector{UInt8}, Tuple{UnitRange{Int64}}, true}, structtype::DataType)
> @ JSONLines ~/work/JSONLines.jl/JSONLines.jl/src/utils.jl:107
> [11] _materialize(buf::Vector{UInt8}, rows::Vector{Int64}, indices::UnitRange{Int64}, names::Tuple{Symbol}, structtype::Type)
> @ JSONLines ~/work/JSONLines.jl/JSONLines.jl/src/utils.jl:165
> [12] materialize(lines::LineIndex{JSONLines.var"##jsonlwebsite.jsonl#140"}, rows::UnitRange{Int64})
> @ JSONLines ~/work/JSONLines.jl/JSONLines.jl/src/LineIndex.jl:91
> [13] materialize
> @ ~/work/JSONLines.jl/JSONLines.jl/src/LineIndex.jl:88 [inlined]
> [14] |>(x::LineIndex{JSONLines.var"##jsonlwebsite.jsonl#140"}, f::typeof(materialize))
> @ Base ./operators.jl:973
> [15] top-level scope
> @ ~/work/JSONLines.jl/JSONLines.jl/test/runtests.jl:56
> [16] macro expansion
> @ ~/hostedtoolcache/julia/nightly/aarch64/share/julia/stdlib/v1.13/Test/src/Test.jl:1952 [inlined]
> [17] macro expansion
> @ ~/work/JSONLines.jl/JSONLines.jl/test/runtests.jl:56 [inlined]
> [18] include(mapexpr::Function, mod::Module, _path::String)
> @ Base ./Base.jl:309
> [19] top-level scope
> @ none:6
> [20] eval(m::Module, e::Any)
> @ Core ./boot.jl:489
> [21] exec_options(opts::Base.JLOptions)
> @ Base ./client.jl:296
> [22] _start()
> @ Base ./client.jl:563
> 
> ```

Is there an easy fix using `Base.invokelatest`?

This is the failing code?

```julia-auto
"""
@MStructType name fieldnames...

This macro gives a convenient syntax for declaring mutable `StructType`s for reading specific variables from a JSONLines file. Also defines `row[:col]` access for rows of the resulting type.

* `name`: Name of the `StructType`
* `fieldnames...`: Names of the variables to be read (must be the same as in the file)
"""
macro MStructType(name, fieldnames...)
quote
    mutable struct $name
        $(fieldnames...)
        $(esc(name))() = new(fill(missing, $(esc(length(fieldnames))))...)
    end
    StructTypes.StructType(::Type{$(esc(name))}) = StructTypes.Mutable()
    StructTypes.names(::Type{$(esc(name))}) = tuple()
    Base.getindex(x::$(esc(name)), col::Symbol) = getproperty(x, col)
end
end

function MStructType(name, vars...)
eval(:(@MStructType $name $(vars...)))
end

macro readcols(path::String, nworkers, cols...)
    name = gensym(basename(path))
    MStructType(name, cols...)
    quote
       LineIndex($path, structtype = $name, nworkers = $nworkers)
    end
end

"""
    readcols(path::String, cols...; nworkers = 1) => LineIndex

* `path`: Path to JSONLines file
* `cols...`: Columnnames to be selected
* Keyword Argument:
    * `nworkers=1`: Number of threads to use for operations on the resulting LineIndex
"""
function readcols(path::String, cols...; nworkers = 1)
    eval(:(@readcols $path $nworkers $(cols...)))
end

```

Edit:  
it wasn’t the obvious: [JSONLines.jl/src/sugar.jl at bf59d43ce0570fb74c40c668fa69093a8c34cc03 · dwinkler1/JSONLines.jl · GitHub](https://github.com/dwinkler1/JSONLines.jl/blob/bf59d43ce0570fb74c40c668fa69093a8c34cc03/src/sugar.jl#L43)

---

<div class="post-metadata">

**Author:** ![giordano](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/giordano/32/2166_2.png) [@giordano](https://discourse.julialang.org/u/giordano)\
**Post date:** [September 8, 2025, 10:31am UTC](https://discourse.julialang.org/t/calling-a-macro-in-a-function-with-eval-fails-on-nightly/132168/2 "2025-09-08T10:31:40Z")

</div>

I don’t have answers to your questions, but I do have suggestions for how to make life of other people who may have the same issue easier.

> [@danielw2904](#):
>
> This fails on the Julia nightly: [Refactor readcols calls to remove JL prefix · dwinkler1/JSONLines.jl@40116ad · GitHub](https://github.com/dwinkler1/JSONLines.jl/actions/runs/17546283476/job/49828390861#step:6:202)

Can you please copy here the full error message? CI logs are ephemeral (will disappear in a few months) and non-searchable on the Internet, which makes finding the same issue later impossible. Also, that would make your request for help self-sufficient, so that people motivate to help you don’t have to go and read some other pages.

> [@danielw2904](#):
>
> it wasn’t the obvious: [JSONLines.jl/src/sugar.jl at master · dwinkler1/JSONLines.jl · GitHub](https://github.com/dwinkler1/JSONLines.jl/blob/master/src/sugar.jl)

That’s a non-permanent link, you want to link [JSONLines.jl/src/sugar.jl at bf59d43ce0570fb74c40c668fa69093a8c34cc03 · dwinkler1/JSONLines.jl · GitHub](https://github.com/dwinkler1/JSONLines.jl/blob/bf59d43ce0570fb74c40c668fa69093a8c34cc03/src/sugar.jl) instead (you can obtain this link by either pressing Y in your browser, the URL will be updated, or by clicking the three dots on the top-right corner of the page and then click on “Copy permalink”)

---

<div class="post-metadata">

**Author:** ![danielw2904](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/danielw2904/32/10890_2.png) [@danielw2904](https://discourse.julialang.org/u/danielw2904)\
**Post date:** [September 9, 2025, 3:49am UTC](https://discourse.julialang.org/t/calling-a-macro-in-a-function-with-eval-fails-on-nightly/132168/3 "2025-09-09T03:49:23Z")

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Thank you for your suggestions! I’ve updated the post accordingly.