optimize C import block handle logic (#131)

* optimize C import block handle logic

Signed-off-by: Loong <loong.dai@intel.com>

* update comments

Signed-off-by: Loong <loong.dai@intel.com>

* bump up

Signed-off-by: Loong <loong.dai@intel.com>

README.md

@@ -23,6 +23,8 @@ By default, blank and dot sections are not used and the corresponding lines end
 
 All import blocks use one TAB(`\t`) as Indent.
 
+Since v0.9.0, GCI always puts C import block as the first.
+
 **Note**:
 
 `nolint` is hard to handle at section level, GCI will consider it as a single comment.

main.go

@@ -6,7 +6,7 @@ import (
 	"github.com/daixiang0/gci/cmd/gci"
 )
 
-var version = "0.8.5"
+var version = "0.9.0"
 
 func main() {
 	e := gci.NewExecutor(version)

pkg/gci/gci.go

@@ -121,7 +121,7 @@ func LoadFormatGoFile(file io.FileObj, cfg config.Config) (src, dist []byte, err
 		return src, src, nil
 	}
 
-	imports, headEnd, tailStart, err := parse.ParseFile(src, file.Path())
+	imports, headEnd, tailStart, cStart, cEnd, err := parse.ParseFile(src, file.Path())
 	if err != nil {
 		if errors.Is(err, parse.NoImportError{}) {
 			return src, src, nil
@@ -162,6 +162,12 @@ func LoadFormatGoFile(file io.FileObj, cfg config.Config) (src, dist []byte, err
 	copy(tail, src[tailStart:])
 
 	head = append(head, utils.Linebreak)
+	// ensure C
+	if cStart != 0 {
+		head = append(head, src[cStart:cEnd]...)
+		head = append(head, utils.Linebreak)
+	}
+
 	// add beginning of import block
 	head = append(head, `import (`...)
 	// add end of import block

pkg/gci/internal/testdata/cgo-block-after-import.cfg.yaml

@@ -0,0 +1 @@
+common.cfg.yaml

pkg/gci/internal/testdata/cgo-block-after-import.in.go

@@ -0,0 +1,14 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/daixiang0/gci"
+	g "github.com/golang"
+)
+
+// #cgo CFLAGS: -DPNG_DEBUG=1
+// #cgo amd64 386 CFLAGS: -DX86=1
+// #cgo LDFLAGS: -lpng
+// #include <png.h>
+import "C"

pkg/gci/internal/testdata/cgo-block-after-import.out.go

@@ -0,0 +1,15 @@
+package main
+
+// #cgo CFLAGS: -DPNG_DEBUG=1
+// #cgo amd64 386 CFLAGS: -DX86=1
+// #cgo LDFLAGS: -lpng
+// #include <png.h>
+import "C"
+
+import (
+	"fmt"
+
+	g "github.com/golang"
+
+	"github.com/daixiang0/gci"
+)

pkg/gci/internal/testdata/cgo-block-before-import.cfg.yaml

@@ -0,0 +1 @@
+common.cfg.yaml

pkg/gci/internal/testdata/cgo-single.cfg.yaml

@@ -0,0 +1 @@
+common.cfg.yaml

pkg/gci/internal/testdata/cgo-single.in.go

@@ -0,0 +1,15 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/daixiang0/gci"
+)
+
+import "C"
+
+import "github.com/golang"
+
+import (
+  "github.com/daixiang0/gci"
+)

pkg/gci/internal/testdata/cgo-single.out.go

@@ -0,0 +1,11 @@
+package main
+
+import "C"
+
+import (
+	"fmt"
+
+	"github.com/golang"
+
+	"github.com/daixiang0/gci"
+)

pkg/parse/parse.go

@@ -70,31 +70,36 @@ func getImports(imp *ast.ImportSpec) (start, end int, name string) {
 	return
 }
 
-func ParseFile(src []byte, filename string) (ImportList, int, int, error) {
+func ParseFile(src []byte, filename string) (ImportList, int, int, int, int, error) {
 	fileSet := token.NewFileSet()
 	f, err := parser.ParseFile(fileSet, filename, src, parser.ParseComments)
 	if err != nil {
-		return nil, 0, 0, err
+		return nil, 0, 0, 0, 0, err
 	}
 
 	if len(f.Imports) == 0 {
-		return nil, 0, 0, NoImportError{}
+		return nil, 0, 0, 0, 0, NoImportError{}
 	}
 
 	var (
 		// headEnd means the start of import block
 		headEnd int
 		// tailStart means the end + 1 of import block
 		tailStart int
-		data      ImportList
+		// cStart means the start of C import block
+		cStart int
+		// cEnd means the end of C import block
+		cEnd int
+		data ImportList
 	)
 
-	for _, d := range f.Decls {
-		switch d.(type) {
+	for index, decl := range f.Decls {
+		switch decl.(type) {
+		// skip BadDecl and FuncDecl
 		case *ast.GenDecl:
-			dd := d.(*ast.GenDecl)
+			genDecl := decl.(*ast.GenDecl)
 
-			if dd.Tok == token.IMPORT {
+			if genDecl.Tok == token.IMPORT {
 				// there are two cases, both end with linebreak:
 				// 1.
 				// import (
@@ -103,35 +108,58 @@ func ParseFile(src []byte, filename string) (ImportList, int, int, error) {
 				// 2.
 				// import "xxx"
 				if headEnd == 0 {
-					headEnd = int(d.Pos()) - 1
+					headEnd = int(decl.Pos()) - 1
+				}
+				tailStart = int(decl.End())
+
+				for _, spec := range genDecl.Specs {
+					imp := spec.(*ast.ImportSpec)
+					// there are only one C import block
+					// ensure C import block is the first import block
+					if imp.Path.Value == C {
+						/*
+							common case:
+
+							// #include <png.h>
+							import "C"
+
+							notice that decl.Pos() == genDecl.Pos() > genDecl.Doc.Pos()
+						*/
+						if genDecl.Doc != nil {
+							cStart = int(genDecl.Doc.Pos()) - 1
+							// if C import block is the first, update headEnd
+							if index == 0 {
+								headEnd = cStart
+							}
+						} else {
+							/*
+								special case:
+
+								import "C"
+							*/
+							cStart = int(decl.Pos()) - 1
+						}
+
+						cEnd = int(decl.End())
+
+						continue
+					}
+
+					start, end, name := getImports(imp)
+
+					data = append(data, &GciImports{
+						Start: start,
+						End:   end,
+						Name:  name,
+						Path:  strings.Trim(imp.Path.Value, `"`),
+					})
 				}
-				tailStart = int(d.End())
-			}
-		}
-	}
-
-	for _, imp := range f.Imports {
-		if imp.Path.Value == C {
-			if imp.Comment != nil {
-				headEnd = int(imp.Comment.End())
-			} else {
-				headEnd = int(imp.Path.End())
 			}
-			continue
 		}
-
-		start, end, name := getImports(imp)
-
-		data = append(data, &GciImports{
-			Start: start,
-			End:   end,
-			Name:  name,
-			Path:  strings.Trim(imp.Path.Value, `"`),
-		})
 	}
 
 	sort.Sort(data)
-	return data, headEnd, tailStart, nil
+	return data, headEnd, tailStart, cStart, cEnd, nil
 }
 
 // IsGeneratedFileByComment reports whether the source file is generated code.