Hugo panics when running with -s exampleSite in v0.123.x

[markdumay]

What version of Hugo are you using (hugo version)?

hugo v0.123.3-a75a659f6fc0cb3a52b2b2ba666a81f79a459376+extended darwin/arm64 BuildDate=2024-02-23T17:09:20Z VendorInfo=brew

Does this issue reproduce with the latest release?

Yes

Context

When upgrading Hugo from v0.122.0 to v0.123.3 I get a Hugo panic. Below the full error logs (specific to the mod-leaflet module):

Full logs

Start building sites … 
hugo v0.123.3-a75a659f6fc0cb3a52b2b2ba666a81f79a459376+extended darwin/arm64 BuildDate=2024-02-23T17:09:20Z VendorInfo=brew

panic: not supported [recovered]
	panic: interface conversion: string is not error: missing method Error

goroutine 25 [running]:
github.com/spf13/fsync.(*Syncer).syncRecover.func1()
	github.com/spf13/fsync@v0.10.0/fsync.go:132 +0xac
panic({0x104063b40?, 0x1044a48f0?})
	runtime/panic.go:770 +0x124
github.com/bep/overlayfs.(*Dir).Read(0x8000?, {0x104063bc0?, 0x14000749501?, 0x100966154?})
	github.com/bep/overlayfs@v0.9.1/overlayfs.go:391 +0x2c
io.copyBuffer({0x12ca25a00, 0x1400015ed00}, {0x12ca25a20, 0x1400015eee0}, {0x0, 0x0, 0x0})
	io/io.go:429 +0x18c
io.Copy(...)
	io/io.go:388
github.com/spf13/fsync.(*Syncer).sync(0x14000749d28, {0x14000a54140, 0xd}, {0x14000a54170, 0xd})
	github.com/spf13/fsync@v0.10.0/fsync.go:173 +0x588
github.com/spf13/fsync.(*Syncer).sync.func1({0x12c9c8760, 0x1400037a540})
	github.com/spf13/fsync@v0.10.0/fsync.go:199 +0xf0
github.com/spf13/fsync.withDirEntry({0x1044d39d8?, 0x1400000e030?}, {0x103eb7d28?, 0x200000003?}, 0x14000749b80)
	github.com/spf13/fsync@v0.10.0/fsync.go:343 +0x2a8
github.com/spf13/fsync.(*Syncer).sync(0x14000749d28, {0x103eb7d28, 0x1}, {0x103eb7d28, 0x1})
	github.com/spf13/fsync@v0.10.0/fsync.go:196 +0x2ac
github.com/spf13/fsync.(*Syncer).syncRecover(0x14000749d28?, {0x103eb7d28?, 0x1?}, {0x103eb7d28?, 0x1?})
	github.com/spf13/fsync@v0.10.0/fsync.go:136 +0x58
github.com/spf13/fsync.(*Syncer).Sync(0x14000749d28, {0x103eb7d28, 0x1}, {0x103eb7d28, 0x1})
	github.com/spf13/fsync@v0.10.0/fsync.go:111 +0xa0
github.com/gohugoio/hugo/commands.(*hugoBuilder).copyStaticTo(0x14000b93100, 0x14000754120)
	github.com/gohugoio/hugo/commands/hugobuilder.go:445 +0x1e4
github.com/gohugoio/hugo/commands.(*hugoBuilder).doWithPublishDirs(0x14000b93100, 0x14000749ef8)
	github.com/gohugoio/hugo/commands/hugobuilder.go:472 +0x13c
github.com/gohugoio/hugo/commands.(*hugoBuilder).copyStatic(0x140003fa960?)
	github.com/gohugoio/hugo/commands/hugobuilder.go:403 +0x34
github.com/gohugoio/hugo/commands.(*hugoBuilder).fullBuild.func2()
	github.com/gohugoio/hugo/commands/hugobuilder.go:507 +0x28
golang.org/x/sync/errgroup.(*Group).Go.func1()
	golang.org/x/sync@v0.6.0/errgroup/errgroup.go:78 +0x58
created by golang.org/x/sync/errgroup.(*Group).Go in goroutine 1
	golang.org/x/sync@v0.6.0/errgroup/errgroup.go:75 +0x98

To reproduce

git clone https://github.com/gethinode/mod-leaflet.git
cd mod-leaflet
hugo mod vendor
hugo --gc --minify -s exampleSite

Notes

I'm transitioning the various modules maintained by gethinode to take advantage of work files (see gethinode/hinode#786), which might prevent this issue. Nevertheless, it seemed to make sense to submit this issue anyways.

[bep]

OK, I have a failing test case for this now and I will fix this.

  [[module.imports.mounts]]
    source = "dist"
    target = "static"
  [[module.imports.mounts]]
    source = "dist/leaflet.scss"
    target = "static/leaflet.css"

My logic didn't handle the "double mounts" above and paniced when it tried to read the directory as a file. You can workaround this by ... removing the single file mount (and rename or copy the source file).

I have reimplemented and simplified the file mounts in Hugo, and I obviously missed some cases where the old code worked, but at least I can now understand my own code :-)

But I will fix, thanks for the report.

[markdumay]

Thanks @bep!

I agree the “double” mounting is a bit odd. The module is basically wrapping an existing npm package to modularize it for Hugo. I was trying to avoid an additional npm script to rename/copy an existing dist file…

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