I am trying to use Go's plugin system. Even with a very basic example, I'm unable to find any symbols in a compiled plugin. My setup looks like this:
/Users/blah/test-workspace/
src/
main/
main.go
plug/
plug.go
plug.go looks like this:
package main
type B struct {}
func main() {}
From the /Users/blah/test-workspace/ directory, I build this using:
GOPATH="/Users/blah/test-workspace" go build -buildmode plugin plug
This produces p.so inside the root of the GOPATH. Next I try to load this plugin via main/main.go:
package main
import (
"fmt"
"plugin"
"os"
)
func main() {
plugin, err := plugin.Open("plug.so")
if err != nil {
fmt.Printf("Error: %+v\n", err)
os.Exit(1)
}
fmt.Printf("%+v\n", plugin)
}
The output of this code is:
&{pluginpath:plug err: loaded:0xc420088060 syms:map[]}
As you can, the symbol map is empty. What am I doing wrong?
From the plugin docs
A symbol is any exported variable or function
You need to add an exported variable or function in order for your plugin to work.
Related
Is there a way to check if a public function/struct is used outside of the package in which it's declared? I'm not writing a public go module that's consumed anywhere else, and simply want to scan whether func Foo() it's used anywhere in my codebase outside of the package in which it's declared.
I'm using GoLand but any programmatic solution would do.
Simplest solution: manually rename Foo() to Foo2(). Build/compile your project: if there are no compilation errors, it's not referenced in your code. Same check also works with any identifiers and with any IDEs (this doesn't use any of the IDE's features).
Obviously if you already have a Foo2 identifier, this will fail. But the idea is to rename it to a non-existing identifier...
You can scan a particular package to see all the available function in it.
In this main.go, app the root package name and there is another package in database directory under the package name database.
By running the code you will found all the function name available inside database package
package main
import (
"fmt"
"app/database"
"go/ast"
"go/parser"
"go/token"
"os"
)
// Name of the package you want to scan
const subPackage = "database"
func main() {
set := token.NewFileSet()
packs, err := parser.ParseDir(set, subPackage, nil, 0)
if err != nil {
fmt.Println("Failed to parse package:", err)
os.Exit(1)
}
funcs := []*ast.FuncDecl{}
for _, pack := range packs {
for _, f := range pack.Files {
for _, d := range f.Decls {
if fn, isFn := d.(*ast.FuncDecl); isFn {
funcs = append(funcs, fn)
}
}
}
}
fmt.Println("All the functions in the package:",subPackage)
for _, fn := range funcs {
fmt.Println(fn.Name.Name)
}
// database Package is called/used
database.Connection()
}
This will get all function declarations in the stated subpackage as an ast.FuncDecl. This isn't an invokable function; it's just a representation of its source code of it.
If you wanted to do anything like call these functions, you'd have to do something more sophisticated. After gathering these functions, you could gather them and output a separate file that calls each of them, then run the resulting file.
I am attempting to create named loggers automatically for HTTP handlers that I'm writing, where I am passed a function (pointer).
I'm using the code mentioned in this question to get the name of a function:
package utils
import (
"reflect"
"runtime"
)
func GetFunctionName(fn interface{}) string {
value := reflect.ValueOf(fn)
ptr := value.Pointer()
ffp := runtime.FuncForPC(ptr)
return ffp.Name()
}
I'm using this in my main function to try it out like so:
package main
import (
"github.com/naftulikay/golang-webapp/experiments/functionname/long"
"github.com/naftulikay/golang-webapp/experiments/functionname/long/nested/path"
"github.com/naftulikay/golang-webapp/experiments/functionname/utils"
"log"
)
type Empty struct{}
func main() {
a := long.HandlerA
b := path.HandlerB
c := path.HandlerC
log.Printf("long.HandlerA: %s", utils.GetFunctionName(a))
log.Printf("long.nested.path.HandlerB: %s", utils.GetFunctionName(b))
log.Printf("long.nested.path.HandlerC: %s", utils.GetFunctionName(c))
}
I see output like this:
github.com/naftulikay/golang-webapp/experiments/functionname/long.HandlerA
This is okay but I'd like an output such as long.HandlerA, long.nested.path.HandlerB, etc.
If I could get the Go module name (github.com/naftulikay/golang-webapp/experiments/functionname), I can then use strings.Replace to remove the module name to arrive at long/nested/path.HandlerB, then strings.Replace to replace / with . to finally get to my desired value, which is long.nested.path.HandlerB.
The first question is: can I do better than runtime.FuncForPC(reflect.ValueOf(fn).Pointer()) for getting the qualified path to a function?
If the answer is no, is there a way to get the current Go module name using runtime or reflect so that I can transform the output of runtime.FuncForPC into what I need?
Once again, I'm getting values like:
github.com/naftulikay/golang-webapp/experiments/functionname/long.HandlerA
github.com/naftulikay/golang-webapp/experiments/functionname/long/nested/path.HandlerB
github.com/naftulikay/golang-webapp/experiments/functionname/long/nested/path.HandlerC
And I'd like to get values like:
long.HandlerA
long.nested.path.HandlerB
long.nested.path.HandlerC
EDIT: It appears that Go does not have a runtime representation of modules, and that's okay, if I can do it at compile time that would be fine too. I've seen the codegen documentation and I'm having a hard time figuring out how to write my own custom codegen that can be used from go generate.
The module info is included in the executable binary, and can be acquired using the debug.ReadBuildInfo() function (the only requirement is that the executable must be built using module support, but this is the default in the current version, and likely the only in future versions).
BuildInfo.Path is the current module's path.
Let's say you have the following go.mod file:
module example.com/foo
Example reading the build info:
bi, ok := debug.ReadBuildInfo()
if !ok {
log.Printf("Failed to read build info")
return
}
fmt.Println(bi.Main.Path)
// or
fmt.Println(bi.Path)
This will output (try it on the Go Playground):
example.com/foo
example.com/foo
See related: Golang - How to display modules version from inside of code
If your goal is to just have the name of the module available in your program, and if you are okay with setting this value at link time, then you may use the -ldflags build option.
You can get the name of the module with go list -m from within the module directory.
You can place everything in a Makefile or in a shell script:
MOD_NAME=$(go list -m)
go build -ldflags="-X 'main.MODNAME=$MOD_NAME'" -o main ./...
With main.go looking like:
package main
import "fmt"
var MODNAME string
func main() {
fmt.Println(MODNAME) // example.com
}
With the mentioned "golang.org/x/mod/modfile" package, an example might look like:
package main
import (
"fmt"
"golang.org/x/mod/modfile"
_ "embed"
)
//go:embed go.mod
var gomod []byte
func main() {
f, err := modfile.Parse("go.mod", gomod, nil)
if err != nil {
panic(err)
}
fmt.Println(f.Module.Mod.Path) // example.com
}
However embedding the entire go.mod file in your use case seems overkill. Of course you could also open the file at runtime, but that means you have to deploy go.mod along with your executable. Setting the module name with -ldflags is more straightforward IMO.
I'm discovering generator (go generate) and I'm trying to generate Validation function for my struct.
The idea is that I don't want my program to use reflect at runtime, I would rather have a generator use reflect to generate the actual method I want to use.
the problem is I can't import my structs in the generator code, the only way I found so far was to read the .go file from the generator and manually parse the types defined there using regex
I've got something like
models/models.go:
package models
//go:generate go run ../generator.go -file models.go
type MyStruct struct {
...
}
generator.go:
package main
func main() {
f, err := ioutil.ReadFile(fileName) // I read filename from the flag provided
...
// I parse f to generate my stuff
}
I would very much prefer to have an introspection package that would take a go code as a string and give me some information about the struct defined there
Or maybe there is a way to import the file that call go:generate to get directly access to the types
There is no need to specify file name , this code does the same :
//go:generate go run ../generator.go -file $GOFILE
With help of text/template package you are needless of parsing the file. A very simple example would be something like this. This will give you the clue :
package main
import (
"flag"
"os"
"text/template"
)
//go:generate go run main.go -name=A
//go:generate go run main.go -name=B
//go:generate go run main.go -name=C
var name = flag.String("name", "test", "name of struct")
var code = `
package main
type Struct{{.}} struct {}
func (s *Struct{{.}} ) Vailadte() bool {
return true
}
`
func main() {
flag.Parse()
file, _ := os.Create(*name + ".go")
defer file.Close()
tmpl, _ := template.New("test").Parse(code)
tmpl.Execute(file, *name)
}
Maybe you can utilize go/parser and go/ast in your generator.
Is there an API to get the module name of a project which uses go 1.11 module system?
so I need to get abc.com/a/m from the module definition module abc.com/a/m in go.mod file.
As of this writing, I am not aware of any exposed APIs for that. However, looking at go mod sources, there is a function that can be quite useful in Go mod source file
// ModulePath returns the module path from the gomod file text.
// If it cannot find a module path, it returns an empty string.
// It is tolerant of unrelated problems in the go.mod file.
func ModulePath(mod []byte) string {
//...
}
func main() {
src := `
module github.com/you/hello
require rsc.io/quote v1.5.2
`
mod := ModulePath([]byte(src))
fmt.Println(mod)
}
Which outputs github.com/you/hello
Try this?
package main
import (
"fmt"
"io/ioutil"
"os"
modfile "golang.org/x/mod/modfile"
)
const (
RED = "\033[91m"
RESET = "\033[0m"
)
func main() {
modName := GetModuleName()
fmt.Fprintf(os.Stdout, "modName=%+v\n", modName)
}
func exitf(beforeExitFunc func(), code int, format string, args ...interface{}) {
beforeExitFunc()
fmt.Fprintf(os.Stderr, RED+format+RESET, args...)
os.Exit(code)
}
func GetModuleName() string {
goModBytes, err := ioutil.ReadFile("go.mod")
if err != nil {
exitf(func() {}, 1, "%+v\n", err)
}
modName := modfile.ModulePath(goModBytes)
fmt.Fprintf(os.Stdout, "modName=%+v\n", modName)
return modName
}
If your starting point is a go.mod file and you are asking how to parse it, I would suggest starting with go mod edit -json, which outputs a particular go.mod file in JSON format. Here is the documentation:
https://golang.org/cmd/go/#hdr-Edit_go_mod_from_tools_or_scripts
Alternatively, you could use rogpeppe/go-internal/modfile, which is a go package that can parse a go.mod file, and which is used by rogpeppe/gohack and some other tools from the broader community.
Issue #28101 I think tracks adding a new API to the Go standard library to parse go.mod files.
Here is a snippet of the documentation for go mod edit -json:
The -json flag prints the final go.mod file in JSON format instead of
writing it back to go.mod. The JSON output corresponds to these Go
types:
type Module struct {
Path string
Version string
}
type GoMod struct {
Module Module
Go string
Require []Require
Exclude []Module
Replace []Replace
}
type Require struct {
Path string
Version string
Indirect bool
}
Here is an example snippet of JSON output from go mod edit -json that shows the actual module path (aka module name), which was your original question:
{
"Module": {
"Path": "rsc.io/quote"
},
In this case, the module name is rsc.io/quote.
As of Go 1.12 (for those finding this via a search who are using modules but not necessarily the older version the OP mentioned), the runtime/debug package includes functionality for getting information about the build, including the module name. For example:
import (
"fmt"
"runtime/debug"
)
func main() {
info, _ := debug.ReadBuildInfo()
fmt.Printf("info: %+v", info.Main.Path)
}
You can run this example on the playground: https://go.dev/play/p/5oGbCRxSnjM
For more information, see the documentation for "runtime/debug".BuildInfo
I am working on testing an application of mine, for which I need to create temporary files with specific extensions. My goal is to create files in a temp directory that look similar to this example123.ac.json.
In order to do this I am using ioutil.TempDir and ioutil.TempFile.
Here is a small contrived example of what I am doing.
main.go:
package main
func main() {
}
main_test.go:
package main
import (
"fmt"
"io/ioutil"
"os"
"testing"
)
func TestMain(t *testing.T) {
dir, err := ioutil.TempDir("", "testing")
if err != nil {
t.Fatalf("unable to create temp directory for testing")
}
defer os.RemoveAll(dir)
file, err := ioutil.TempFile(dir, "*.ac.json") // Create a temporary file with '.ac.json' extension
if err != nil {
t.Fatalf("unable to create temporary file for testing")
}
fmt.Printf("created the following file: %v\n", file.Name())
}
When I run the tests locally on my Mac with go test the following is outputted from the fmt.Printf is
$ go test
created the following file: /var/folders/tj/1_mxwn350_d2c5r9b_2zgy7m0000gn/T/testing566832606/900756901.ac.json
PASS
ok github.com/JonathonGore/travisci-bug 0.004s
So it works as expected but when I run it in TravisCI the following is outputted from the Printf statement:
created the following file: /tmp/testing768620677/*.ac.json193187872
For some reason it is using the literal asterisk inside TravisCI but not when running on my own computer.
Here is a link to the TravisCI logs if interested.
For completeness here is my .travis.yml:
language: go
go:
- "1.10"
Anyone have any idea what is going on here? Or am I missing something obvious?
The feature of replacing the first asterisk with the random value was added in Go 1.11. It looks like you are using go 1.10 for your Travis CI runs so the asterisk won't be replaced.