Panic in ParsePlaceholders function in placeholders.go

[kavinsan]

I've came across a panic caused by an unsafe slice access

`panic: runtime error: index out of range [0] with length 0

goroutine 42 [running]:
github.com/lukasjarosch/go-docx.assembleFullPlaceholders(0xc00056abe0, {0xc000764500, 0x1, 0x2}, {0x0, 0x0, 0x0})
/Users/kav/go/pkg/mod/github.com/lukasjarosch/[email protected]/placeholder.go:272 +0x285
github.com/lukasjarosch/go-docx.ParsePlaceholders({0xc00058e000, 0x112, 0x200}, {0xc0005ee000, 0xc741, 0xe000})
/Users/kav/go/pkg/mod/github.com/lukasjarosch/[email protected]/placeholder.go:196 +0xf4c
github.com/lukasjarosch/go-docx.newDocument(0xc000488508, {0xc0001802a0, 0x57}, 0xc0001916f0)
/Users/kav/go/pkg/mod/github.com/lukasjarosch/[email protected]/document.go:126 +0x7a7
github.com/lukasjarosch/go-docx.Open({0xc0001802a0, 0x57})
/Users/kav/go/pkg/mod/github.com/lukasjarosch/[email protected]/document.go:70 +0x405
main.DocxToPdfClient.InsertDataIntoDocument({}, 0xc0005d82a0, {0x0, 0x0, 0x0}, {0xc0001802a0, 0x57})
/Users/kav/go/src/github.com/EnergyWell/pdf-service/app/docx_to_pdf.go:33 +0x2cf
main.(*MergeFilesToPdfClient).ConvertNonPdfSourceFilesToPdf(0xc00002ba28, {0x24b6590, 0x2c2e740})
/Users/kav/go/src/github.com/EnergyWell/pdf-service/app/merge_pdfs.go:104 +0x1f0
main.(*service).MergeFilesToPdf(0xc0001080f0, {0x24ba590, 0xc0005d8a80}, 0xc0001dc3f0)
/Users/kav/go/src/github.com/EnergyWell/pdf-service/app/pdfservice.go:198 +0xd3e
github.com/EnergyWell/pdf-service/proto._PdfService_MergeFilesToPdf_Handler.func1({0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0})
/Users/kav/go/src/github.com/EnergyWell/pdf-service/proto/pdf_generator.pb.go:958 +0xf2
github.com/mwitkow/go-grpc-middleware.ChainUnaryServer.func1.1({0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0})
/Users/kav/go/pkg/mod/github.com/mwitkow/[email protected]/chain.go:31 +0xea
github.com/EnergyWell/authorization.(*authorizer).authorizeAdminOnly(0xc000108140, {0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0}, 0xc00052e520, 0xc0001f48c0)
/Users/kav/go/pkg/mod/github.com/!energy!well/[email protected]/authorization.go:132 +0x1a4
github.com/EnergyWell/authorization.(*authorizer).Middleware(0xc000108140, {0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0}, 0xc00052e520, 0xc0001f48c0)
/Users/kav/go/pkg/mod/github.com/!energy!well/[email protected]/authorization.go:68 +0x447
github.com/mwitkow/go-grpc-middleware.ChainUnaryServer.func1.1({0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0})
/Users/kav/go/pkg/mod/github.com/mwitkow/[email protected]/chain.go:34 +0x212
github.com/EnergyWell/auth.(*AuthMiddleware).UnaryMiddleware(0xc0003d4f20, {0x24ba590, 0xc0005d8a80}, {0x214f740, 0xc0001dc3f0}, 0xc00052e520, 0xc0001f48c0)
/Users/kav/go/pkg/mod/github.com/!energy!well/[email protected]/middleware.go:77 +0x51a
github.com/mwitkow/go-grpc-middleware.ChainUnaryServer.func1.1({0x24ba590, 0xc0005d8300}, {0x214f740, 0xc0001dc3f0})
/Users/kav/go/pkg/mod/github.com/mwitkow/[email protected]/chain.go:34 +0x212
github.com/EnergyWell/service/logger.UnaryMiddleware({0x24ba590, 0xc0005d8300}, {0x214f740, 0xc0001dc3f0}, 0xc00052e520, 0xc0001f48c0)
/Users/kav/go/pkg/mod/github.com/!energy!well/[email protected]/logger/middleware.go:39 +0x3e6
github.com/mwitkow/go-grpc-middleware.ChainUnaryServer.func1({0x24ba590, 0xc0005d8270}, {0x214f740, 0xc0001dc3f0}, 0xc00052e520, 0xc0000121f8)
/Users/kav/go/pkg/mod/github.com/mwitkow/[email protected]/chain.go:39 +0x2a6
github.com/EnergyWell/pdf-service/proto._PdfService_MergeFilesToPdf_Handler({0x20f0900, 0xc0001080f0}, {0x24ba590, 0xc0005d8270}, 0xc0001aa420, 0xc000446450)
/Users/kav/go/src/github.com/EnergyWell/pdf-service/proto/pdf_generator.pb.go:960 +0x216
google.golang.org/grpc.(*Server).processUnaryRPC(0xc00044c000, {0x24bdcb8, 0xc0004d1520}, 0xc000504000, 0xc0004762a0, 0x2bec360, 0x0)
/Users/kav/go/pkg/mod/google.golang.org/[email protected]/server.go:1282 +0x15e3
google.golang.org/grpc.(*Server).handleStream(0xc00044c000, {0x24bdcb8, 0xc0004d1520}, 0xc000504000, 0x0)
/Users/kav/go/pkg/mod/google.golang.org/[email protected]/server.go:1616 +0x891
google.golang.org/grpc.(*Server).serveStreams.func1.2()
/Users/kav/go/pkg/mod/google.golang.org/[email protected]/server.go:921 +0x117
created by google.golang.org/grpc.(*Server).serveStreams.func1 in goroutine 57
/Users/kav/go/pkg/mod/google.golang.org/[email protected]/server.go:919 +0x385`

[lukasjarosch]

Thanks for reporting this, I'll check it out after work 👍🏼

[PanicIsReal]

Any idea what may be causing this? I am experiencing the same issue.

[kavinsan]

Any idea what may be causing this? I am experiencing the same issue.

For me it was using a template with the wrong placeholder. Note the extra {}
Ex.

• Bad: {{ some_key }}
• Good: {some_key}

Hopefully we get a patch for this soon! :)

[TeCHiScy]

Hopefully we get a patch for this soon! :)

I will take a look at this too.

Update 1: I have reproduced the panic. The essential of the panic is that in a Run, there's more than one openDelims, but no closeDelims (or may be len(openDelims) > len(closeDelims) + 1). I created two cases, as below:

1. The template provided is corrupted, e.g. {{holder,
2. The template was acceptable, but the Run was divided, e.g. {{{holder}}}, and in the xml it was divided as {{|{holder}|}}. Here, | represents the divider.

Update 2: A PR that refactors ParsePlaceholders to avoid the aforesaid panic (as well as make itself more concise and adaptable) is work in process. This refactor may also lay a foundation for #28. I'm testing the new function. Once the PR is ready, I'll update here.

Update 3: Hi @PanicIsReal, @kavinsan, could you please attach a minimal reproducible example (i.e., your docx and the replace map) here, so I can use this as test cases to see if my PR #32 works well now.

Update 4: Unresolved issue, if a placeholder cross table cells (or any hard boundaries that should not be crossed), it is also replaced. (if allowed, then it may be messed up when some kind of template engine introduced). Besides, this weird behavior in fact relies on the order of runs in xml, which is unexpected to users.