Involved Source Filesbuild.go
Package build gathers information about Go packages.
The Go path is a list of directory trees containing Go source code.
It is consulted to resolve imports that cannot be found in the standard
Go tree. The default path is the value of the GOPATH environment
variable, interpreted as a path list appropriate to the operating system
(on Unix, the variable is a colon-separated string;
on Windows, a semicolon-separated string;
on Plan 9, a list).
Each directory listed in the Go path must have a prescribed structure:
The src/ directory holds source code. The path below 'src' determines
the import path or executable name.
The pkg/ directory holds installed package objects.
As in the Go tree, each target operating system and
architecture pair has its own subdirectory of pkg
If DIR is a directory listed in the Go path, a package with
source in DIR/src/foo/bar can be imported as "foo/bar" and
has its compiled form installed to "DIR/pkg/GOOS_GOARCH/foo/bar.a"
(or, for gccgo, "DIR/pkg/gccgo/foo/libbar.a").
The bin/ directory holds compiled commands.
Each command is named for its source directory, but only
using the final element, not the entire path. That is, the
command with source in DIR/src/foo/quux is installed into
DIR/bin/quux, not DIR/bin/foo/quux. The foo/ is stripped
so that you can add DIR/bin to your PATH to get at the
Here's an example directory layout:
bar/ (go code in package bar)
quux/ (go code in package main)
quux (installed command)
bar.a (installed package object)
A build constraint, also known as a build tag, is a line comment that begins
that lists the conditions under which a file should be included in the
package. Build constraints may also be part of a file's name
(for example, source_windows.go will only be included if the target
operating system is windows).
See 'go help buildconstraint'
(https://golang.org/cmd/go/#hdr-Build_constraints) for details.
In Go 1.12 and earlier, it was possible to distribute packages in binary
form without including the source code used for compiling the package.
The package was distributed with a source file not excluded by build
constraints and containing a "//go:binary-only-package" comment. Like a
build constraint, this comment appeared at the top of a file, preceded
only by blank lines and other line comments and with a blank line
following the comment, to separate it from the package documentation.
Unlike build constraints, this comment is only recognized in non-test
Go source files.
The minimal source code for a binary-only package was therefore:
The source code could include additional Go code. That code was never
compiled but would be processed by tools like godoc and might be useful
as end-user documentation.
"go build" and other commands no longer support binary-only-packages.
Import and ImportDir will still set the BinaryOnly flag in packages
containing these comments for use in tools and error messages.
Package-Level Type Names (total 5)
/* sort by: | */
A Context specifies the supporting context for a build.
The build, tool, and release tags specify build constraints
that should be considered satisfied when processing +build lines.
Clients creating a new context may customize BuildTags, which
defaults to empty, but it is usually an error to customize ToolTags or ReleaseTags.
ToolTags defaults to build tags appropriate to the current Go toolchain configuration.
ReleaseTags defaults to the list of Go releases the current release is compatible with.
BuildTags is not set for the Default build Context.
In addition to the BuildTags, ToolTags, and ReleaseTags, build constraints
consider the values of GOARCH and GOOS as satisfied tags.
The last element in ReleaseTags is assumed to be the current release.
// whether cgo files are included
// compiler to assume when computing target paths
Dir is the caller's working directory, or the empty string to use
the current directory of the running process. In module mode, this is used
to locate the main module.
If Dir is non-empty, directories passed to Import and ImportDir must
// target architecture
// target operating system
// Go path
// Go root
HasSubdir reports whether dir is lexically a subdirectory of
root, perhaps multiple levels below. It does not try to check
whether dir exists.
If so, HasSubdir sets rel to a slash-separated path that
can be joined to root to produce a path equivalent to dir.
If HasSubdir is nil, Import uses an implementation built on
The install suffix specifies a suffix to use in the name of the installation
directory. By default it is empty, but custom builds that need to keep
their outputs separate can set InstallSuffix to do so. For example, when
using the race detector, the go command uses InstallSuffix = "race", so
that on a Linux/386 system, packages are written to a directory named
"linux_386_race" instead of the usual "linux_386".
IsAbsPath reports whether path is an absolute path.
If IsAbsPath is nil, Import uses filepath.IsAbs.
IsDir reports whether the path names a directory.
If IsDir is nil, Import calls os.Stat and uses the result's IsDir method.
JoinPath joins the sequence of path fragments into a single path.
If JoinPath is nil, Import uses filepath.Join.
OpenFile opens a file (not a directory) for reading.
If OpenFile is nil, Import uses os.Open.
ReadDir returns a slice of fs.FileInfo, sorted by Name,
describing the content of the named directory.
If ReadDir is nil, Import uses ioutil.ReadDir.
SplitPathList splits the path list into a slice of individual paths.
If SplitPathList is nil, Import uses filepath.SplitList.
// use files regardless of +build lines, file names
Import returns details about the Go package named by the import path,
interpreting local import paths relative to the srcDir directory.
If the path is a local import path naming a package that can be imported
using a standard import path, the returned package will set p.ImportPath
to that path.
In the directory containing the package, .go, .c, .h, and .s files are
considered part of the package except for:
- .go files in package documentation
- files starting with _ or . (likely editor temporary files)
- files with build constraints not satisfied by the context
If an error occurs, Import returns a non-nil error and a non-nil
*Package containing partial information.
ImportDir is like Import but processes the Go package found in
the named directory.
MatchFile reports whether the file with the given name in the given directory
matches the context and would be included in a Package created by ImportDir
of that directory.
MatchFile considers the name of the file and may use ctxt.OpenFile to
read some or all of the file's content.
SrcDirs returns a list of package source root directories.
It draws from the current Go root and Go path but omits directories
that do not exist.
func go/internal/srcimporter.New(ctxt *Context, fset *token.FileSet, packages map[string]*types.Package) *srcimporter.Importer
MultiplePackageError describes a directory containing
multiple buildable Go source files for multiple packages.
// directory containing files
// corresponding files: Files[i] declares package Packages[i]
// package names found
(*T) Error() string
*T : error
NoGoError is the error used by Import to describe a directory
containing no buildable Go source files. (It may still contain
test files, files hidden by build tags, and so on.)
Dirstring(*T) Error() string
*T : error
A Package describes the Go package found in a directory.
// tags that can influence file selection in this directory
// command install directory ("" if unknown)
// cannot be rebuilt from source (has //go:binary-only-package comment)
// .c source files
// .cc, .cpp and .cxx source files
// Cgo CFLAGS directives
// Cgo CPPFLAGS directives
// Cgo CXXFLAGS directives
// Cgo FFLAGS directives
// .go source files that import "C"
// Cgo LDFLAGS directives
// Cgo pkg-config directives
// this directory shadows Dir in $GOPATH
// directory containing package sources
// documentation synopsis
// line information for EmbedPatterns
//go:embed patterns found in Go source files
For example, if a source file says
//go:embed a* b.c
then the list will contain those two strings as separate entries.
(See package embed for more details about //go:embed.)
// patterns from GoFiles, CgoFiles
// .f, .F, .for and .f90 Fortran source files
// .go source files (excluding CgoFiles, TestGoFiles, XTestGoFiles)
// package found in Go root
// .h, .hh, .hpp and .hxx source files
// .go source files ignored for this build (including ignored _test.go files)
// non-.go source files ignored for this build
// path in import comment on package statement
// import path of package ("" if unknown)
// line information for Imports
// import paths from GoFiles, CgoFiles
// .go source files with detected problems (parse error, wrong package name, and so on)
// .m (Objective-C) source files
// package name
// installed .a file
// package install root directory ("" if unknown)
// architecture dependent install root directory ("" if unknown)
// root of Go tree where this package lives
// .s source files
// package source root directory ("" if unknown)
// .swigcxx files
// .swig files
// .syso system object files to add to archive
// line information for TestEmbedPatterns
// patterns from TestGoFiles
// _test.go files in package
// line information for TestImports
// import paths from TestGoFiles
// line information for XTestEmbedPatternPos
// patterns from XTestGoFiles
// _test.go files outside package
// line information for XTestImports
// import paths from XTestGoFiles
IsCommand reports whether the package is considered a
command to be installed (not just a library).
Packages named "main" are treated as commands.
func Import(path, srcDir string, mode ImportMode) (*Package, error)
func ImportDir(dir string, mode ImportMode) (*Package, error)
func (*Context).Import(path string, srcDir string, mode ImportMode) (*Package, error)
func (*Context).ImportDir(dir string, mode ImportMode) (*Package, error)
Package-Level Functions (total 4)
ArchChar returns "?" and an error.
In earlier versions of Go, the returned string was used to derive
the compiler and linker tool names, the default object file suffix,
and the default linker output name. As of Go 1.5, those strings
no longer vary by architecture; they are compile, link, .o, and a.out, respectively.
Import is shorthand for Default.Import.
ImportDir is shorthand for Default.ImportDir.
IsLocalImport reports whether the import path is
a local import path, like ".", "..", "./foo", or "../foo".
Package-Level Variables (total 2)
Default is the default Context for builds.
It uses the GOARCH, GOOS, GOROOT, and GOPATH environment variables
if set, or else the compiled code's GOARCH, GOOS, and GOROOT.
ToolDir is the directory containing build tools.
Package-Level Constants (total 4)
If AllowBinary is set, Import can be satisfied by a compiled
package object without corresponding sources.
The supported way to create a compiled-only package is to
write source code containing a //go:binary-only-package comment at
the top of the file. Such a package will be recognized
regardless of this flag setting (because it has source code)
and will have BinaryOnly set to true in the returned Package.
If FindOnly is set, Import stops after locating the directory
that should contain the sources for a package. It does not
read any files in the directory.
By default, Import searches vendor directories
that apply in the given source directory before searching
the GOROOT and GOPATH roots.
If an Import finds and returns a package using a vendor
directory, the resulting ImportPath is the complete path
to the package, including the path elements leading up
to and including "vendor".
For example, if Import("y", "x/subdir", 0) finds
"x/vendor/y", the returned package's ImportPath is "x/vendor/y",
not plain "y".
See golang.org/s/go15vendor for more information.
Setting IgnoreVendor ignores vendor directories.
In contrast to the package's ImportPath,
the returned package's Imports, TestImports, and XTestImports
are always the exact import paths from the source files:
Import makes no attempt to resolve or check those paths.
If ImportComment is set, parse import comments on package statements.
Import returns an error if it finds a comment it cannot understand
or finds conflicting comments in multiple source files.
See golang.org/s/go14customimport for more information.
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