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go/doc/comment: failure to recognize initial code block #61373

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ghost opened this issue Jul 15, 2023 · 7 comments
Closed

go/doc/comment: failure to recognize initial code block #61373

ghost opened this issue Jul 15, 2023 · 7 comments
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Documentation help wanted NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@ghost
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ghost commented Jul 15, 2023

What version of Go are you using (go version)?

go version go1.20 windows/amd64

What operating system and processor architecture are you using (go env)?

go env Output
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Steven\AppData\Local\go-build
set GOENV=C:\Users\Steven\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Steven\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Steven\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=D:\go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=D:\go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.20
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=NUL
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=C:\Windows\TEMP\go-build2119281587=/tmp/go-build -gno-record-gcc-switches

What did you do?

if I run this code:

package main

import (
   "go/doc/comment"
   "os"
)

const pass = `one
 two
 three`

const fail = ` two
 three`

func main() {
   {
      d := new(comment.Parser).Parse(pass)
      b := new(comment.Printer).HTML(d)
      os.Stdout.Write(b)
   }
   os.Stdout.WriteString("\n")
   {
      d := new(comment.Parser).Parse(fail)
      b := new(comment.Printer).HTML(d)
      os.Stdout.Write(b)
   }
}

What did you expect to see?

<p>one
<pre>two
three
</pre>

<pre>two
three
</pre>

What did you see instead?

<p>one
<pre>two
three
</pre>

<p>two
three

it seems the first input gives expected output, but the second does not. from what I can tell, both inputs match the definition of a code block:

A code block is a span of indented or blank lines not starting with a bullet list marker or numbered list marker.

https://go.dev/doc/comment#code
@AndrewHarrisSPU
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Interesting - subtly, I think the implementation has a notion of common indentation. By tweaking the relative amount of whitespace it's possible to get different parses (https://go.dev/play/p/-MM0d5hDbYk).

Is this a documentation thing? I couldn't pick out this behavior from the documentation directly or infer it from subtle details it does cover. The package doc for Parser.Parse says:

Parse parses the doc comment text and returns the *Doc form. Comment markers (/* // and */) in the text must have already been removed.

Would "Comment markers and indentation common to all lines in text" be enough of a tweak?

@ghost
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ghost commented Jul 15, 2023

Is this a documentation thing?

I would prefer if the current behavior was an error, because I would like the freedom to start a comment with a code block, which seems is not currently possible. but if I had to guess, I would say the current behavior is correct, and that the documentation needs to be improved.

Would "Comment markers and indentation common to all lines in text" be enough of a tweak?

I dont think so. I think this behavior is unexpected enough that it should be special cased in the documentation, assuming the current behavior is correct. so something like:

it is not possible to start a comment with a code block.

@AndrewHarrisSPU
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I would like the freedom to start a comment with a code block

I think this is possible? In https://go.dev/play/p/-MM0d5hDbYk just having the opening line have more spaces in front seemed to set it into a <pre> block

@ghost
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ghost commented Jul 15, 2023

yes, I just noticed that as well. it seems the current restriction would more accurately be:

it is not possible to have only a code block as a comment. a code block must be accompanied by at least one leading or trailing line

@seankhliao seankhliao added Documentation NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jul 17, 2023
@bcmills bcmills added this to the Backlog milestone Jul 17, 2023
@ghost ghost closed this as completed Aug 27, 2023
@ianlancetaylor
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This is happening because the go/doc/comment parser first strips any indentation that appears consistently in every line. If you change your example to

const fail = ` two
 three
four`

then the initial code block is recognized.

Stripping consistent indentation is a heuristic that seems to work reasonably well in practice.

@ghost ghost reopened this Aug 27, 2023
@ghost
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ghost commented Aug 27, 2023

ideally I would like to be able to have a code block only comment, which is not currently possible. however failing that, I think it would be helpful to at least document that its a known shortcoming that you cannot do that.

@gopherbot
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Change https://go.dev/cl/524039 mentions this issue: _content/doc/comment: document removal of common prefix

willpoint pushed a commit to orijtech/website that referenced this issue Oct 17, 2023
@ianlancetaylor @willpoint
_content/doc/comment: document removal of common prefix
88e235d 
Fixes golang/go#61373

Change-Id: I60fa1be13cb7e32af5169e303f5e1c40d207edc4
Reviewed-on: https://go-review.googlesource.com/c/website/+/524039
Reviewed-by: Russ Cox <rsc@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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