From 6d91d473f24d6825170e494852b26ffc748fe542 Mon Sep 17 00:00:00 2001
From: Teddy Wing
Date: Sun, 14 May 2023 21:21:06 +0200
Subject: Find `go` statements using Go analyzer

Build a basic Go analyser that finds `go` statements.

Currently testing this with:

    $ go run ./cmd/gocapturedrefrace ./testdata/

Using the following tutorials as a guide:

* https://arslan.io/2019/06/13/using-go-analysis-to-write-a-custom-linter/
* https://scribe.rip/codex/writing-custom-linter-in-go-54ef6f8080
---
 .gitignore                    |  1 +
 cmd/gocapturedrefrace/main.go | 10 ++++++++++
 go.mod                        | 10 ++++++++++
 go.sum                        |  7 +++++++
 gocapturedrefrace.go          | 45 +++++++++++++++++++++++++++++++++++++++++++
 testdata/simple.go            |  9 +++++++++
 6 files changed, 82 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 cmd/gocapturedrefrace/main.go
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 gocapturedrefrace.go
 create mode 100644 testdata/simple.go

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..fd1a426
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/private/
diff --git a/cmd/gocapturedrefrace/main.go b/cmd/gocapturedrefrace/main.go
new file mode 100644
index 0000000..d637a38
--- /dev/null
+++ b/cmd/gocapturedrefrace/main.go
@@ -0,0 +1,10 @@
+package main
+
+import (
+	"git.teddywing.com/gocapturedrefrace"
+	"golang.org/x/tools/go/analysis/singlechecker"
+)
+
+func main() {
+	singlechecker.Main(gocapturedrefrace.Analyzer)
+}
diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..218c9d0
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,10 @@
+module git.teddywing.com/gocapturedrefrace
+
+go 1.20
+
+require golang.org/x/tools v0.9.1
+
+require (
+	golang.org/x/mod v0.10.0 // indirect
+	golang.org/x/sys v0.8.0 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..cf10794
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,7 @@
+golang.org/x/mod v0.10.0 h1:lFO9qtOdlre5W1jxS3r/4szv2/6iXxScdzjoBMXNhYk=
+golang.org/x/mod v0.10.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
+golang.org/x/sync v0.2.0 h1:PUR+T4wwASmuSTYdKjYHI5TD22Wy5ogLU5qZCOLxBrI=
+golang.org/x/sys v0.8.0 h1:EBmGv8NaZBZTWvrbjNoL6HVt+IVy3QDQpJs7VRIw3tU=
+golang.org/x/sys v0.8.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/tools v0.9.1 h1:8WMNJAz3zrtPmnYC7ISf5dEn3MT0gY7jBJfw27yrrLo=
+golang.org/x/tools v0.9.1/go.mod h1:owI94Op576fPu3cIGQeHs3joujW/2Oc6MtlxbF5dfNc=
diff --git a/gocapturedrefrace.go b/gocapturedrefrace.go
new file mode 100644
index 0000000..762473b
--- /dev/null
+++ b/gocapturedrefrace.go
@@ -0,0 +1,45 @@
+package gocapturedrefrace
+
+import (
+	"bytes"
+	"go/ast"
+	"go/printer"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+var Analyzer = &analysis.Analyzer{
+	Name: "gocapturedrefrace",
+	Doc:  "reports captured references in goroutine closures",
+	Run:  run,
+}
+
+func run(pass *analysis.Pass) (interface{}, error) {
+	for _, file := range pass.Files {
+		ast.Inspect(
+			file,
+			func(node ast.Node) bool {
+				goStmt, ok := node.(*ast.GoStmt)
+				if !ok {
+					return true
+				}
+
+				var printedNode bytes.Buffer
+				err := printer.Fprint(&printedNode, pass.Fset, goStmt)
+				if err != nil {
+					panic(err)
+				}
+
+				pass.Reportf(
+					goStmt.Pos(),
+					"go statement found %q",
+					printedNode,
+				)
+
+				return true
+			},
+		)
+	}
+
+	return nil, nil
+}
diff --git a/testdata/simple.go b/testdata/simple.go
new file mode 100644
index 0000000..496be52
--- /dev/null
+++ b/testdata/simple.go
@@ -0,0 +1,9 @@
+package main
+
+func main() {
+	capturedReference := 0
+
+	go func() {
+		capturedReference += 1
+	}()
+}
-- 
cgit v1.2.3