Handle empty backtraces (#185)

Fixes #184

Author: timholy

src/backedges.jl

@@ -1,6 +1,6 @@
 # A lightly-modified version of the same function in Base
 # Highlights argument types with color specified by highlighter(typ)
-function show_tuple_as_call(@nospecialize(highlighter), io::IO, name::Symbol, @nospecialize(sig::Type), demangle=false, kwargs=nothing)
+function show_tuple_as_call(@nospecialize(highlighter), io::IO, name::Symbol, @nospecialize(sig::Type), demangle=false #=, kwargs=nothing =#)
     if sig === Tuple
         print(io, demangle ? Base.demangle_function_name(name) : name, "(...)")
         return
@@ -34,16 +34,16 @@ function show_tuple_as_call(@nospecialize(highlighter), io::IO, name::Symbol, @n
         first = false
         printstyled(env_io, "::", sig[i], color=highlighter(sig[i]))
     end
-    if kwargs !== nothing
-        print(io, "; ")
-        first = true
-        for (k, t) in kwargs
-            first || print(io, ", ")
-            first = false
-            print(io, k, "::")
-            show(io, t)
-        end
-    end
+    # if kwargs !== nothing
+    #     print(io, "; ")
+    #     first = true
+    #     for (k, t) in kwargs
+    #         first || print(io, ", ")
+    #         first = false
+    #         print(io, k, "::")
+    #         show(io, t)
+    #     end
+    # end
     print(io, ")")
     Base.show_method_params(io, tv)
     nothing
@@ -89,22 +89,23 @@ nextnode(mi, edge) = edge
 instance(sfs::Vector{StackTraces.StackFrame}) = sfs[end].linfo
 method(sfs::Vector{StackTraces.StackFrame}) = method(instance(sfs))
 
-instance(ipframes::Vector{IPFrames}) = instance(ipframes[1].sfs)
+instance(ipframes::Vector{IPFrames}) = isempty(ipframes) ? nothing : instance(ipframes[1].sfs)
 backedges(ipframes::Vector{IPFrames}) = (ret = ipframes[2:end]; isempty(ret) ? () : (ret,))
 
 function callstring(io, mi)
     show_tuple_as_call(nonconcrete_red, IOContext(io, :color=>true), method(mi).name, specTypes(mi))
     return String(take!(io))
 end
 function callstring(io, sfs::Vector{StackTraces.StackFrame})
+    isempty(sfs) && return ""
     for i = 1:length(sfs)-1
         sf = sfs[i]
         print(io, sf.func, " at ", sf.file, ':', sf.line, " => ")
     end
     sf = sfs[end]
     return callstring(io, instance(sfs)) * string(" at ", sf.file, ':', sf.line)
 end
-callstring(io, ipframes::Vector{IPFrames}) = callstring(io, ipframes[1].sfs)
+callstring(io, ipframes::Vector{IPFrames}) = isempty(ipframes) ? "" : callstring(io, ipframes[1].sfs)
 
 struct Data{T}
     callstr::String

test/runtests.jl

@@ -411,12 +411,27 @@ fst5(x) = fst4(x)
     root = Cthulhu.treelist(mi)
     @test occursin("Vararg", root.data.callstr)
 
+    # Test highlighting and other printing
+    mi = Cthulhu.get_specialization(:, Tuple{T, T} where T<:Integer)
+    root = Cthulhu.treelist(mi)
+    @test occursin("\e[31m::T\e[39m", root.data.callstr)
+    mi = Cthulhu.get_specialization(Vector{Int}, Tuple{typeof(undef), Int})
+    io = IOBuffer()
+    @test Cthulhu.callstring(io, mi) == "Vector{$Int}(::UndefInitializer, ::$Int)"
+    mi = Cthulhu.get_specialization(similar, Tuple{Type{Vector{T}}, Dims{1}} where T)
+    @test occursin(r"31m::Type", Cthulhu.callstring(io, mi))
+
     # treelist for stacktraces
     tree = Cthulhu.treelist(fst5(1.0))
     @test match(r"fst1 at .*:\d+ => fst2 at .*:\d+ => fst3\(::Float64\) at .*:\d+", tree.data.callstr) !== nothing
     @test length(tree.children) == 1
     child = tree.children[1]
     @test match(r" fst4 at .*:\d+ => fst5\(::Float64\) at .*:\d+", child.data.callstr) !== nothing
+
+    # issue #184
+    tree = Cthulhu.treelist(similar(fst5(1.0), 0))
+    @test isempty(tree.data.callstr)
+    @test isempty(Cthulhu.callstring(io, similar(stacktrace(fst5(1.0)), 0)))
 end
 
 @testset "ascend" begin