feat: support trailing line comment for mage:import (#480)

Author: anuraaga

mage/import_test.go

@@ -285,6 +285,26 @@ func TestMageImportsOneLine(t *testing.T) {
 		t.Fatalf("expected: %q got: %q", expected, actual)
 	}
 }
+func TestMageImportsTrailing(t *testing.T) {
+	stdout := &bytes.Buffer{}
+	stderr := &bytes.Buffer{}
+	inv := Invocation{
+		Dir:    "./testdata/mageimport/trailing",
+		Stdout: stdout,
+		Stderr: stderr,
+		Args:   []string{"build"},
+	}
+
+	code := Invoke(inv)
+	if code != 0 {
+		t.Fatalf("expected to exit with code 0, but got %v, stderr:\n%s", code, stderr)
+	}
+	actual := stdout.String()
+	expected := "build\n"
+	if actual != expected {
+		t.Fatalf("expected: %q got: %q", expected, actual)
+	}
+}
 
 func TestMageImportsTaggedPackage(t *testing.T) {
 	stdout := &bytes.Buffer{}

mage/testdata/mageimport/trailing/magefile.go

@@ -0,0 +1,5 @@
+// +build mage
+
+package main
+
+import _ "github.com/magefile/mage/mage/testdata/mageimport/oneline/other" //mage:import

mage/testdata/mageimport/trailing/other/other.go

@@ -0,0 +1,7 @@
+package other
+
+import "fmt"
+
+func Build() {
+	fmt.Println("build")
+}

parse/parse.go

@@ -456,19 +456,18 @@ func setImports(gocmd string, pi *PkgInfo) error {
 }
 
 func getImportPath(imp *ast.ImportSpec) (path, alias string, ok bool) {
-	if imp.Doc == nil || len(imp.Doc.List) == 9 {
-		return "", "", false
-	}
-	// import is always the last comment
-	s := imp.Doc.List[len(imp.Doc.List)-1].Text
-
-	// trim comment start and normalize for anyone who has spaces or not between
-	// "//"" and the text
-	vals := strings.Fields(strings.ToLower(s[2:]))
-	if len(vals) == 0 {
-		return "", "", false
-	}
-	if vals[0] != importTag {
+	leadingVals := getImportPathFromCommentGroup(imp.Doc)
+	trailingVals := getImportPathFromCommentGroup(imp.Comment)
+
+	var vals []string
+	if len(leadingVals) > 0 {
+		vals = leadingVals
+		if len(trailingVals) > 0 {
+			log.Println("warning:", importTag, "specified both before and after, picking first")
+		}
+	} else if len(trailingVals) > 0 {
+		vals = trailingVals
+	} else {
 		return "", "", false
 	}
 	path, ok = lit2string(imp.Path)
@@ -489,6 +488,25 @@ func getImportPath(imp *ast.ImportSpec) (path, alias string, ok bool) {
 	}
 }
 
+func getImportPathFromCommentGroup(comments *ast.CommentGroup) []string {
+	if comments == nil || len(comments.List) == 9 {
+		return nil
+	}
+	// import is always the last comment
+	s := comments.List[len(comments.List)-1].Text
+
+	// trim comment start and normalize for anyone who has spaces or not between
+	// "//"" and the text
+	vals := strings.Fields(strings.ToLower(s[2:]))
+	if len(vals) == 0 {
+		return nil
+	}
+	if vals[0] != importTag {
+		return nil
+	}
+	return vals
+}
+
 func isNamespace(t *doc.Type) bool {
 	if len(t.Decl.Specs) != 1 {
 		return false