mirror of
https://github.com/golang/go
synced 2024-11-24 00:10:04 -07:00
doc: update "How to Write Go Code" to use the go tool
R=golang-dev, r, kevlar, rsc CC=golang-dev https://golang.org/cl/5534045
This commit is contained in:
parent
014c342b1e
commit
d9b82baac1
327
doc/code.html
327
doc/code.html
@ -45,120 +45,89 @@ that receives a message summarizing each checkin to the Go repository.
|
||||
|
||||
<h2 id="New_package">Creating a new package</h2>
|
||||
|
||||
<h3>Choosing an import path</h3>
|
||||
|
||||
<p>
|
||||
The source code for the package with import path
|
||||
<code>x/y</code> is, by convention, kept in the
|
||||
directory <code>$GOROOT/src/pkg/x/y</code>.
|
||||
The standard packages are given short names like <code>fmt</code> and
|
||||
<code>net/http</code> for convenience.
|
||||
For your own projects, choose a name space that is unlikely
|
||||
to collide with future additions to the standard library or other
|
||||
external libraries.
|
||||
</p>
|
||||
|
||||
<h3>Makefile</h3>
|
||||
<p>
|
||||
For instance, if your source repository is at <code>example.com</code>
|
||||
or <code>code.google.com/p/example</code>, you should begin your package
|
||||
paths with that URL, as in "<code>example.com/foo/bar</code>" or
|
||||
"<code>code.google.com/p/example/foo/bar</code>".
|
||||
This way the <a href="/cmd/go/"><code>go</code> tool</a> can automatically
|
||||
check out and build the source code from its import path.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
It would be nice to have Go-specific tools that
|
||||
inspect the source files to determine what to build and in
|
||||
what order, but for now, Go uses GNU <code>make</code>.
|
||||
Thus, the first file to create in a new package directory is
|
||||
usually the <code>Makefile</code>.
|
||||
The basic form used in the Go source tree
|
||||
is illustrated by <a href="../src/pkg/container/vector/Makefile"><code>src/pkg/container/vector/Makefile</code></a>:
|
||||
If you don't intend your code to be installed in this way, you should at
|
||||
least use a unique prefix like "<code>widgets/</code>", as in
|
||||
"<code>widgets/foo/bar</code>". A good rule is to use a prefix such as your
|
||||
company or project name since it is unlikely to be used by another group.
|
||||
</p>
|
||||
|
||||
|
||||
<h3>The <code>go</code> tool and <code>GOPATH</code></h3>
|
||||
|
||||
<p>
|
||||
The <a href="/cmd/go/"><code>go</code> tool</a> is the standard means of
|
||||
building and installing Go libraries and programs. It is a "zero configuration"
|
||||
tool; it determines how to build Go packages from their source code alone.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
To use the <code>go</code> tool effectively you must set the
|
||||
<code>GOPATH</code> variable.
|
||||
<code>GOPATH</code> specifies a list of paths that contain Go source code
|
||||
and package binaries. Source code, package objects, and command binaries are
|
||||
located inside the <code>GOPATH</code>s' <code>src</code>, <code>pkg</code>,
|
||||
and <code>bin</code> subdirectories respectively.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
You should set <code>GOPATH</code> in your shell profile
|
||||
(<code>$HOME/.bashrc</code>, <code>$HOME/.profile</code>, or equivalent).
|
||||
</p>
|
||||
|
||||
<p>
|
||||
This shell session demonstrates setting <code>GOPATH</code>, creating a trivial
|
||||
<code>widgets/foo</code> package, and building and installing the package.
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
include ../../../Make.inc
|
||||
|
||||
TARG=container/vector
|
||||
GOFILES=\
|
||||
intvector.go\
|
||||
stringvector.go\
|
||||
vector.go\
|
||||
|
||||
include ../../../Make.pkg
|
||||
$ export GOPATH=$HOME/gocode
|
||||
$ mkdir -p $GOPATH/src/widgets/foo
|
||||
$ cat > $GOPATH/src/widgets/foo/foo.go
|
||||
package foo
|
||||
const String = "Go rules!"
|
||||
^D
|
||||
$ go install widgets/foo
|
||||
$ ls $GOPATH/pkg/*/example
|
||||
foo.a
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
Outside the Go source tree (for personal packages), the standard form is
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
include $(GOROOT)/src/Make.inc
|
||||
|
||||
TARG=mypackage
|
||||
GOFILES=\
|
||||
my1.go\
|
||||
my2.go\
|
||||
|
||||
include $(GOROOT)/src/Make.pkg
|
||||
</pre>
|
||||
<p>(<code>^D</code> means to type Control-D.)</p>
|
||||
|
||||
<p>
|
||||
The first and last lines <code>include</code> standard definitions and rules.
|
||||
Packages maintained in the standard Go tree use a relative path (instead of
|
||||
<code>$(GOROOT)/src</code>) so that <code>make</code> will work correctly
|
||||
even if <code>$(GOROOT)</code> contains spaces.
|
||||
This makes it easy for programmers to try Go.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
If you have not set <code>$GOROOT</code> in your environment,
|
||||
you must run <code>gomake</code> to use this form of makefile.
|
||||
<code>Gomake</code> also takes care to invoke GNU Make
|
||||
even on systems where it is installed as <code>gmake</code>
|
||||
rather than <code>make</code>.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
<code>TARG</code> is the target install path for the package,
|
||||
the string that clients will use to import it.
|
||||
Inside the Go tree, this string should be the same as the directory
|
||||
in which the <code>Makefile</code> appears, with the
|
||||
<code>$GOROOT/src/pkg/</code> prefix removed.
|
||||
Outside the Go tree, you can use any <code>TARG</code> you
|
||||
want that doesn't conflict with the standard Go package names.
|
||||
A common convention is to use an identifying top-level name
|
||||
to group your packages: <code>myname/tree</code>, <code>myname/filter</code>, etc.
|
||||
Note that even if you keep your package source outside the
|
||||
Go tree, running <code>make install</code> installs your
|
||||
package binaries in the standard location—<code>$GOROOT/pkg</code>—to
|
||||
make it easy to find them.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
<code>GOFILES</code> is a list of source files to compile to
|
||||
create the package. The trailing <code>\</code> characters
|
||||
allow the list to be split onto multiple lines
|
||||
for easy sorting.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
If you create a new package directory in the Go tree, add it to the list in
|
||||
<code>$GOROOT/src/pkg/Makefile</code> so that it
|
||||
is included in the standard build. Then run:
|
||||
<pre>
|
||||
cd $GOROOT/src/pkg
|
||||
./deps.bash
|
||||
</pre>
|
||||
<p>
|
||||
to update the dependency file <code>Make.deps</code>.
|
||||
(This happens automatically each time you run <code>all.bash</code>
|
||||
or <code>make.bash</code>.)
|
||||
</p>
|
||||
|
||||
<p>
|
||||
If you change the imports of an existing package,
|
||||
you do not need to edit <code>$GOROOT/src/pkg/Makefile</code>
|
||||
but you will still need to run <code>deps.bash</code> as above.
|
||||
Type <code>go help gopath</code> on the command line for more information
|
||||
about <code>GOPATH</code>.
|
||||
</p>
|
||||
|
||||
|
||||
<h3>Go source files</h3>
|
||||
|
||||
<p>
|
||||
The first statement in each of the source files listed in the <code>Makefile</code>
|
||||
should be <code>package <i>name</i></code>, where <code><i>name</i></code>
|
||||
is the package's default name for imports.
|
||||
The first statement in a Go source file should be <code>package
|
||||
<i>name</i></code>, where <code><i>name</i></code> is the package's default
|
||||
name for imports.
|
||||
(All files in a package must use the same <code><i>name</i></code>.)
|
||||
Go's convention is that the package name is the last element of the
|
||||
import path: the package imported as <code>"crypto/rot13"</code>
|
||||
import path: the package imported as "<code>crypto/rot13</code>"
|
||||
should be named <code>rot13</code>.
|
||||
There is no requirement that package names be unique
|
||||
across all packages linked into a single binary,
|
||||
@ -178,63 +147,81 @@ that topic.
|
||||
</p>
|
||||
|
||||
<h2 id="Building_programs">Building programs</h2>
|
||||
<p>To build a Go program with gomake, create a Makefile alongside your program's
|
||||
source files. It should be similar to the example above, but include
|
||||
<code>Make.cmd</code> instead of <code>Make.pkg</code>:
|
||||
|
||||
<pre>
|
||||
include $(GOROOT)/src/Make.inc
|
||||
|
||||
TARG=helloworld
|
||||
GOFILES=\
|
||||
helloworld.go\
|
||||
|
||||
include $(GOROOT)/src/Make.cmd
|
||||
</pre>
|
||||
|
||||
<p>Running <code>gomake</code> will compile <code>helloworld.go</code>
|
||||
and produce an executable named <code>helloworld</code> in the current
|
||||
directory.
|
||||
<p>
|
||||
The <a href="/cmd/go/"><code>go</code> tool</a> treats code belonging to
|
||||
<code>package main</code> as an executable command, and installs the package
|
||||
binary to the <code>GOPATH</code>'s <code>bin</code> subdirectory.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
Running <code>gomake install</code> will build <code>helloworld</code> if
|
||||
necessary and copy it to the <code>$GOBIN</code> directory
|
||||
(<code>$GOROOT/bin/</code> is the default).
|
||||
Building executable commands is the same as building packages.
|
||||
Use "<code>go install</code>":
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
$ cat > $GOPATH/src/widgets/bar/bar.go
|
||||
package main
|
||||
|
||||
import (
|
||||
"fmt"
|
||||
"widgets/foo"
|
||||
)
|
||||
|
||||
func main() {
|
||||
fmt.Println(foo.String)
|
||||
}
|
||||
^D
|
||||
$ go install widgets/bar
|
||||
$ $GOPATH/bin/bar
|
||||
Go rules!
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
Run <code>go help build</code> and <code>go help install</code> for more
|
||||
about building and installing Go binaries.
|
||||
</p>
|
||||
|
||||
<h2 id="Testing">Testing</h2>
|
||||
|
||||
<p>
|
||||
Go has a lightweight test framework known as <code>gotest</code>.
|
||||
Go has a lightweight test framework composed of the <code>go</code> tool and
|
||||
the <code>testing</code> package.
|
||||
You write a test by creating a file with a name ending in <code>_test.go</code>
|
||||
that contains functions named <code>TestXXX</code> with signature <code>func (t *testing.T)</code>.
|
||||
that contains functions named <code>TestXXX</code> with signature
|
||||
<code>func (t *testing.T)</code>.
|
||||
The test framework runs each such function;
|
||||
if the function calls a failure function such as <code>t.Error</code> or <code>t.Fail</code>, the test is considered to have failed.
|
||||
The <a href="/cmd/gotest/">gotest command documentation</a>
|
||||
and the <a href="/pkg/testing/">testing package documentation</a> give more detail.
|
||||
if the function calls a failure function such as <code>t.Error</code> or
|
||||
<code>t.Fail</code>, the test is considered to have failed.
|
||||
Run <code>go help test</code> and see the
|
||||
<a href="/pkg/testing/">testing package documentation</a> for more detail.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
The <code>*_test.go</code> files should not be listed in the <code>Makefile</code>.
|
||||
To run the test, run "<code>go test</code>":
|
||||
</p>
|
||||
|
||||
<p>
|
||||
To run the test, run either <code>make test</code> or <code>gotest</code>
|
||||
(they are equivalent).
|
||||
To run only the tests in a single test file, for instance <code>one_test.go</code>,
|
||||
run <code>gotest one_test.go</code>.
|
||||
</p>
|
||||
<pre>
|
||||
$ cat > $GOPATH/src/widgets/foo/foo_test.go
|
||||
package foo
|
||||
|
||||
import "testing"
|
||||
|
||||
func TestString(t *testing.T) {
|
||||
const expect = "Go rules!"
|
||||
if String != expect {
|
||||
t.Errorf("String == %q, want %q", String, expect)
|
||||
}
|
||||
}
|
||||
^D
|
||||
$ go test widgets/foo
|
||||
ok widgets/foo
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
If your change affects performance, add a <code>Benchmark</code> function
|
||||
(see the <a href="/cmd/gotest/">gotest command documentation</a>)
|
||||
and run it using <code>gotest -test.bench=.</code>.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
Once your new code is tested and working,
|
||||
it's time to get it <a href="contribute.html">reviewed and submitted</a>.
|
||||
(run <code>go help testfunc</code>) and run it using <code>go test
|
||||
-test.bench=.*</code>.
|
||||
</p>
|
||||
|
||||
<h2 id="pkg_example">An example package with tests</h2>
|
||||
@ -242,7 +229,7 @@ it's time to get it <a href="contribute.html">reviewed and submitted</a>.
|
||||
<p>
|
||||
This example package, <code>numbers</code>, consists of the function
|
||||
<code>Double</code>, which takes an <code>int</code> and returns that value
|
||||
multiplied by 2. It consists of three files.
|
||||
multiplied by 2. It consists of two files.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
@ -289,38 +276,24 @@ func TestDouble(t *testing.T) {
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
Finally, the <code>Makefile</code>:
|
||||
</p>
|
||||
|
||||
<pre>
|
||||
include $(GOROOT)/src/Make.inc
|
||||
|
||||
TARG=numbers
|
||||
GOFILES=\
|
||||
numbers.go\
|
||||
|
||||
include $(GOROOT)/src/Make.pkg
|
||||
</pre>
|
||||
|
||||
<p>
|
||||
Running <code>gomake install</code> will build and install the package to
|
||||
the <code>$GOROOT/pkg/</code> directory (it can then be used by any
|
||||
program on the system).
|
||||
Running <code>go install</code> will build and install the package to
|
||||
the <code>GOPATH</code>'s <code>pkg</code> directory
|
||||
(it can then be imported by any other Go program).
|
||||
</p>
|
||||
|
||||
<p>
|
||||
Running <code>gomake test</code> (or just running the command
|
||||
<code>gotest</code>) will rebuild the package, including the
|
||||
Running <code>go test</code> will rebuild the package, including the
|
||||
<code>numbers_test.go</code> file, and then run the <code>TestDouble</code>
|
||||
function. The output "<code>PASS</code>" indicates that all tests passed
|
||||
function. The output "<code>ok</code>" indicates that all tests passed
|
||||
successfully. Breaking the implementation by changing the multiplier from
|
||||
<code>2</code> to <code>3</code> will allow you to see how failing tests are
|
||||
reported.
|
||||
</p>
|
||||
|
||||
<p>
|
||||
See the <a href="/cmd/gotest/">gotest documentation</a> and the
|
||||
<a href="/pkg/testing/">testing package</a> for more detail.
|
||||
Run <code>go help test</code>, <code>go help testfunc</code>,
|
||||
and <code>go help testflag</code> and see the
|
||||
<a href="/pkg/testing/">testing package documentation</a> for more detail.
|
||||
</p>
|
||||
|
||||
<h2 id="arch_os_specific">Architecture- and operating system-specific code</h2>
|
||||
@ -335,34 +308,34 @@ different operating systems.</p>
|
||||
|
||||
<p>To compile such code, use the <code>$GOOS</code> and <code>$GOARCH</code>
|
||||
<a href="/doc/install.html#environment">environment variables</a> in your
|
||||
source file names and <code>Makefile</code>.</p>
|
||||
source file names.</p>
|
||||
|
||||
<p>For example, this <code>Makefile</code> describes a package that builds on
|
||||
<p>For example, consider the package <code>foo</code> that consists of four
|
||||
files:</p>
|
||||
|
||||
<pre>
|
||||
foo.go
|
||||
foo_386.go
|
||||
foo_amd64.go
|
||||
foo_arm.go
|
||||
</pre>
|
||||
|
||||
describes a package that builds on
|
||||
different operating systems by parameterizing the file name with
|
||||
<code>$GOOS</code>.</p>
|
||||
|
||||
<pre>
|
||||
include $(GOROOT)/src/Make.inc
|
||||
<p>The general code goes in <code>foo.go</code>, while architecture-specific
|
||||
code goes in <code>foo_386.go</code>, <code>foo_amd64.go</code>, and
|
||||
<code>foo_arm.go</code>.</p>
|
||||
|
||||
TARG=mypackage
|
||||
GOFILES=\
|
||||
my.go\
|
||||
my_$(GOOS).go\
|
||||
|
||||
include $(GOROOT)/src/Make.pkg
|
||||
</pre>
|
||||
|
||||
<p>The OS-specific code goes in <code>my_linux.go</code>,
|
||||
<code>my_darwin.go</code>, and so on.</p>
|
||||
|
||||
<p>If you follow these conventional parameterizations, tools such as
|
||||
<a href="/cmd/goinstall/">goinstall</a> will work seamlessly with your package:
|
||||
</p>
|
||||
<p>If you follow these conventional parameterizations, tools such as the <a
|
||||
href="/cmd/go/"><code>go</code> tool</a> will work seamlessly with your
|
||||
package:</p>
|
||||
|
||||
<pre>
|
||||
my_$(GOOS).go
|
||||
my_$(GOARCH).go
|
||||
my_$(GOOS)_$(GOARCH).go
|
||||
foo_$GOOS.go
|
||||
foo_$GOARCH.go
|
||||
foo_$GOOS_$GOARCH.go
|
||||
</pre>
|
||||
|
||||
<p>The same holds for <code>.s</code> (assembly) files.</p>
|
||||
<p>The same holds for <code>.s</code> (assembly) and <code>.c</code> files.</p>
|
||||
|
Loading…
Reference in New Issue
Block a user