Make Hugo work with Go 1.11 (and Go 1.10)

[rjoleary]

I'm on the Go master branch, Ubuntu 16.04, Linux 4.4.0-127-generic:

% go version
go version devel +65c365b Wed May 23 23:51:30 2018 +0000 linux/amd64

The following (gotten from getting started) runs as expected:

go get github.com/magefile/mage
go get -d github.com/gohugoio/hugo
cd ${GOPATH:-$HOME/go}/src/github.com/gohugoio/hugo
mage vendor

However, running install fails:

% mage install
# github.com/gohugoio/hugo/tpl/tplimpl
tpl/tplimpl/template_ast_transformers.go:116:18: cannot range over x.Decl (type bool)
tpl/tplimpl/template_ast_transformers.go:132:10: undefined: parse.VariableNode
tpl/tplimpl/template_ast_transformers.go:133:30: an.Ident undefined (type parse.Node has no field or method Ident)
Error: running "go install -ldflags -X github.com/gohugoio/hugo/hugolib.CommitHash=d68367c -X github.com/gohugoio/hugo/hugolib.BuildDate=2018-05-27T08:47:25-0400 github.com/gohugoio/hugo" failed with exit code 2

It appears hugo depends on "text/template/parse" which got an API change on Dec 17 which was merged to master in April:

To avoid confusion, rename PipeNode.Decl to PipeNode.Vars, as the
variables may not always be declared after this change.

Renaming Decl to Vars and VariableNode to AssignNode in "template_ast_transformers.go" allowed Hugo to install:

% hugo version
Hugo Static Site Generator v0.42-DEV-D68367C linux/amd64 BuildDate: 2018-05-27T09:03:03-0400

It seems out of the ordinary for Go to have a breaking change. It would be nice to be able to install hugo with Go master.

[bep]

Go's master branch is not supported. We will eventually fix this.

[anthonyfok]

@rjoleary, Thank you for your report!

PR #4849 (pending review) fixes the compilation issue with the upcoming go1.11.

However, a somewhat unrelated test failed, which @ bep quickly recognize as another behaviour change in go1.11 (nil used to return nothing in go1.10 and before, but not it returns <nil>, and filed golang/go#25875, which upstream will likely fix before the official go1.11 release.

[anthonyfok]

Regarding the escaped <nil> output from html/template in Go tip (pre-Go1.11), i.e. golang/go#25875, upstream has come up with a proposed fix at https://go-review.googlesource.com/c/go/+/118835, pending review and discussion, with a disclaimer at the bottom of the commit message:

DO NOT SUBMIT - we haven't yet decided if this is the right path forward.

Full diff of the proposed fix: https://go.googlesource.com/go/+/46c521a7ee4d04971a828d0c0f9d698e1641344d%5E%21/

[github-actions]

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