Rewrite maximum call in base sysimg.jl to fix error when stdlibs is e… (#325)

* Rewrite maximum call in base sysimg.jl to fix error when stdlibs is empty.

* Add a test for generating an empty sysimage.

Author: fredrikekre

src/PackageCompiler.jl

@@ -103,8 +103,13 @@ function rewrite_sysimg_jl_only_needed_stdlibs(stdlibs::Vector{String})
     sysimg_content = read(sysimg_source_path, String)
     # replaces the hardcoded list of stdlibs in sysimg.jl with
     # the stdlibs that is given as argument
-    return replace(sysimg_content,
+    content = replace(sysimg_content,
         r"stdlibs = \[(.*?)\]"s => string("stdlibs = [", join(":" .* stdlibs, ",\n"), "]"))
+    # Also replace a maximum call which fails for empty collections,
+    # see https://github.com/JuliaLang/julia/pull/34727
+    content = replace(content, "maximum(textwidth.(string.(stdlibs)))" =>
+                               "reduce(max, textwidth.(string.(stdlibs)); init=0)")
+    return content
 end
 
 function create_fresh_base_sysimage(stdlibs::Vector{String}; cpu_target::String)

test/runtests.jl

@@ -71,4 +71,13 @@ end
             @test occursin("HelloWorld artifact at $(realpath(app_compiled_dir))", app_output)
         end
     end
+    # Test creating an empty sysimage
+    if !is_slow_ci
+        tmp = mktempdir()
+        sysimage_path = joinpath(tmp, "empty." * Libdl.dlext)
+        foreach(x -> touch(joinpath(tmp, x)), ["Project.toml", "Manifest.toml"])
+        create_sysimage(; sysimage_path=sysimage_path, incremental=false, filter_stdlibs=true, project=tmp)
+        hello = read(`$(Base.julia_cmd()) -J $(sysimage_path) -e 'print("hello, world")'`, String)
+        @test hello == "hello, world"
+    end
 end