Fixing empty files problem

grantnelson-wf · grantnelson-wf · commit 40c566325653 · 2024-01-17T16:48:55.000-07:00
diff --git a/build/build.go b/build/build.go
@@ -411,13 +411,32 @@ func augmentOriginalFile(file *ast.File, overrides map[string]overrideInfo) {
 	finalizeRemovals(file)
 }
 
+// isOnlyImports determines if this file is empty except for imports.
+func isOnlyImports(file *ast.File) bool {
+	for _, decl := range file.Decls {
+		if gen, ok := decl.(*ast.GenDecl); !ok || gen.Tok != token.IMPORT {
+			return false
+		}
+	}
+	return true
+}
+
 // pruneImports will remove any unused imports from the file.
 //
-// This will not remove any dot (`.`) or blank (`_`) imports.
+// This will not remove any dot (`.`) or blank (`_`) imports, unless
+// there are no declarations or directives meaning that all the imports
+// should be cleared.
 // If the removal of code causes an import to be removed, the init's from that
 // import may not be run anymore. If we still need to run an init for an import
 // which is no longer used, add it to the overlay as a blank (`_`) import.
 func pruneImports(file *ast.File) {
+	if isOnlyImports(file) && !astutil.HasDirectivePrefix(file, `//go:linkname `) {
+		// The file is empty, remove all imports including any `.` or `_` imports.
+		file.Imports = nil
+		file.Decls = nil
+		return
+	}
+
 	unused := make(map[string]int, len(file.Imports))
 	for i, in := range file.Imports {
 		if name := astutil.ImportName(in); len(name) > 0 {
diff --git a/build/build_test.go b/build/build_test.go
@@ -375,8 +375,10 @@ func TestOverlayAugmentation(t *testing.T) {
 			desc: `remove unsafe and embed if not needed`,
 			src: `import "unsafe"
 				import "embed"
+
 				//gopherjs:purge
 				var eFile embed.FS
+
 				//gopherjs:purge
 				func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)`,
 			want: ``,
@@ -388,8 +390,10 @@ func TestOverlayAugmentation(t *testing.T) {
 			desc: `keep unsafe and embed for directives`,
 			src: `import "unsafe"
 				import "embed"
+
 				//go:embed hello.txt
 				var eFile embed.FS
+
 				//go:linkname runtimeNano runtime.nanotime
 				func runtimeNano() int64`,
 			noCodeChange: true,
@@ -565,14 +569,18 @@ func TestOriginalAugmentation(t *testing.T) {
 				`Equal`:   {},
 			},
 			src: `import "cmp"
+			
+				// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}
 
 				type Pointer[T any] struct {}
 
 				func Sort[S ~[]E, E cmp.Ordered](x S) {}
 
 				// overlay had stub "func Equal() {}"
 				func Equal[S ~[]E, E any](s1, s2 S) bool {}`,
-			want: ``,
+			want: `// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}`,
 		}, {
 			desc: `purge generics`,
 			info: map[string]overrideInfo{
@@ -582,6 +590,9 @@ func TestOriginalAugmentation(t *testing.T) {
 			},
 			src: `import "cmp"
 
+				// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}
+
 				type Pointer[T any] struct {}
 				func (x *Pointer[T]) Load() *T {}
 				func (x *Pointer[T]) Store(val *T) {}
@@ -590,12 +601,17 @@ func TestOriginalAugmentation(t *testing.T) {
 
 				// overlay had stub "func Equal() {}"
 				func Equal[S ~[]E, E any](s1, s2 S) bool {}`,
-			want: ``,
+			want: `// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}`,
 		}, {
 			desc: `prune an unused import`,
 			info: map[string]overrideInfo{},
-			src:  `import foo "some/other/bar"`,
-			want: ``,
+			src: `import foo "some/other/bar"
+			
+				// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}`,
+			want: `// keeps the isOnlyImports from skipping what is being tested.
+				func foo() {}`,
 		}, {
 			desc: `override signature of function`,
 			info: map[string]overrideInfo{
@@ -638,6 +654,25 @@ func TestOriginalAugmentation(t *testing.T) {
 					}
 					return b, false
 				}`,
+		}, {
+			desc: `empty file removes all imports`,
+			info: map[string]overrideInfo{
+				`foo`: {},
+			},
+			src: `import . "math/rand"
+				func foo() int {
+					return Int()
+				}`,
+			want: ``,
+		}, {
+			desc: `empty file with directive`,
+			info: map[string]overrideInfo{
+				`foo`: {},
+			},
+			src: `//go:linkname foo bar
+				import _ "unsafe"`,
+			want: `//go:linkname foo bar
+				import _ "unsafe"`,
 		},
 	}
 
