code review 72770043: cmd/go: allow use of Context in 'go list -f'

cmd/go: allow use of Context in 'go list -f'

Add a $Context variable to the template so that the build.Context values
such as BuildTags can be accessed.

Fixes issue 6666.

[rick, 2014-03-08 03:01:16]

Hello golang-codereviews@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go

[gobot, 2014-03-17 22:17:51]

R=adg@golang.org (assigned by adg@golang.org)

[adg, 2014-03-19 21:27:17]

You must run "mkdoc.sh" after updating any documentation strings

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/context.go
File src/cmd/go/context.go (right):

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/context.go#newc...
src/cmd/go/context.go:24: func NewContext(c *build.Context) *Context {
s/New/new/

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go#newcode81
src/cmd/go/list.go:81: defined as:
The global variable $Context is also passed to the template.
It is a subset of the build context (see the type Context in package "go/build"
for details).
The struct is defined as:

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go#newcode154
src/cmd/go/list.go:154: fm := template.FuncMap{"join": strings.Join, "buildCtx":
buildCtx}
I'd expand this a little

fm := template.FuncMap{
  "join": strings.Join,
  "buildCtx": func() *Context { return newContext(&buildContext) },
}
tt := "{{$Context := buildCtx}}" + *listFmt
tmpl, err := template.New("main").Funcs(fm).Parse(tt)

[rick, 2014-03-19 22:10:49]

PTAL

(also ran mkdoc.sh)

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/context.go
File src/cmd/go/context.go (right):

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/context.go#newc...
src/cmd/go/context.go:24: func NewContext(c *build.Context) *Context {
On 2014/03/19 21:27:18, adg wrote:
> s/New/new/

Done.

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go#newcode81
src/cmd/go/list.go:81: defined as:
On 2014/03/19 21:27:18, adg wrote:
> The global variable $Context is also passed to the template.
> It is a subset of the build context (see the type Context in package
"go/build"
> for details).
> The struct is defined as:

Done.

https://codereview.appspot.com/72770043/diff/40001/src/cmd/go/list.go#newcode154
src/cmd/go/list.go:154: fm := template.FuncMap{"join": strings.Join, "buildCtx":
buildCtx}
On 2014/03/19 21:27:18, adg wrote:
> I'd expand this a little
> 
> fm := template.FuncMap{
>   "join": strings.Join,
>   "buildCtx": func() *Context { return newContext(&buildContext) },
> }
> tt := "{{$Context := buildCtx}}" + *listFmt
> tmpl, err := template.New("main").Funcs(fm).Parse(tt)

Done.

[adg, 2014-03-19 22:37:01]

LGTM

leaving for rsc

[gobot, 2014-03-19 22:37:11]

R=rsc@golang.org (assigned by adg@golang.org)

[rsc, 2014-03-24 23:15:04]

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/doc.go
File src/cmd/go/doc.go (right):

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/doc.go#newcode335
src/cmd/go/doc.go:335: The global variable $Context is also passed to the
template.
The template variable $Context contains information about the build context:

    type Context struct {
        ...
    }

See the Context type in the go/build package for more details about the meanings
of the fields.

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/list.go#newcode154
src/cmd/go/list.go:154: "buildCtx": func() *Context { return
newContext(&buildContext) },
It's unfortunate that this name is exposed, and also unfortunate that the
template must be modified before passing to Parse. We can avoid both of these by
making the function named 'context' and drop the $Context entirely.

Then s/buildCtx/context/, drop the tt := below, and the docs change to say

The -f flag specifies an alternate format for the list, using the
syntax of package template.  The default output is equivalent to -f
'{{.ImportPath}}'.  The struct being passed to the template is:

	type Package struct {
		...
	}

The template function "join" calls strings.Join.

The template function "context" returns the build context, defined as:

	type Context struct {
		...
	}

For more information about the meaning of these fields see the documentation
for the go/build package's Context type.

[rick, 2014-03-25 01:18:14]

PTAL

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/doc.go
File src/cmd/go/doc.go (right):

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/doc.go#newcode335
src/cmd/go/doc.go:335: The global variable $Context is also passed to the
template.
On 2014/03/24 23:15:04, rsc wrote:
> The template variable $Context contains information about the build context:
> 
>     type Context struct {
>         ...
>     }
> 
> See the Context type in the go/build package for more details about the
meanings
> of the fields.
> 
> 

Done.

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/60001/src/cmd/go/list.go#newcode154
src/cmd/go/list.go:154: "buildCtx": func() *Context { return
newContext(&buildContext) },
On 2014/03/24 23:15:04, rsc wrote:
> It's unfortunate that this name is exposed, and also unfortunate that the
> template must be modified before passing to Parse. We can avoid both of these
by
> making the function named 'context' and drop the $Context entirely.
> 
> Then s/buildCtx/context/, drop the tt := below, and the docs change to say
> 
> The -f flag specifies an alternate format for the list, using the
> syntax of package template.  The default output is equivalent to -f
> '{{.ImportPath}}'.  The struct being passed to the template is:
> 
> 	type Package struct {
> 		...
> 	}
> 
> The template function "join" calls strings.Join.
> 
> The template function "context" returns the build context, defined as:
> 
> 	type Context struct {
> 		...
> 	}
> 
> For more information about the meaning of these fields see the documentation
> for the go/build package's Context type.

Done.

[rsc, 2014-03-25 01:33:07]

https://codereview.appspot.com/72770043/diff/80001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/80001/src/cmd/go/list.go#newcode153
src/cmd/go/list.go:153: fm := template.FuncMap{
okay, last change:

var cachedCtxt *Context
context := func() *Context {
    if cachedCtxt == nil {
        cachedCtxt = newContext(&buildContext)
    }
    return cachedCtxt
}

and then "context": context in the map.

so that repeated calls to context do not keep allocating copies of the struct
just to extract a single field.

[rick, 2014-03-25 01:48:46]

PTAL

https://codereview.appspot.com/72770043/diff/80001/src/cmd/go/list.go
File src/cmd/go/list.go (right):

https://codereview.appspot.com/72770043/diff/80001/src/cmd/go/list.go#newcode153
src/cmd/go/list.go:153: fm := template.FuncMap{
On 2014/03/25 01:33:07, rsc wrote:
> okay, last change:
> 
> var cachedCtxt *Context
> context := func() *Context {
>     if cachedCtxt == nil {
>         cachedCtxt = newContext(&buildContext)
>     }
>     return cachedCtxt
> }
> 
> and then "context": context in the map.
> 
> so that repeated calls to context do not keep allocating copies of the struct
> just to extract a single field.

Done.

[rsc, 2014-04-08 18:40:15]

LGTM

[adg, 2014-04-08 23:46:18]

Russ, do you intend to submit this or wait until after Go 1.3?

[rsc, 2014-04-09 02:35:33]

*** Submitted as https://code.google.com/p/go/source/detail?r=993c2116e413 ***

cmd/go: allow use of Context in 'go list -f'

Add a $Context variable to the template so that the build.Context values
such as BuildTags can be accessed.

Fixes issue 6666.

LGTM=adg, rsc
R=golang-codereviews, gobot, adg, rsc
CC=golang-codereviews
https://codereview.appspot.com/72770043

Committer: Russ Cox <rsc@golang.org>