Update package's list of imports after we filter out sources.

nevkontakte · nevkontakte · commit 181d09fdea3d · 2021-12-28T19:45:14.000Z
This ensures that callers only see imports that actually remain in the
sources after we excluded irrelevant parts of the upstream package
sources.
diff --git a/build/build.go b/build/build.go
@@ -564,23 +564,7 @@ func (s *Session) BuildPackage(pkg *PackageData) (*compiler.Archive, error) {
 		}
 
 		for _, importedPkgPath := range pkg.Imports {
-			// Ignore all imports that aren't mentioned in import specs of pkg.
-			// For example, this ignores imports such as runtime/internal/sys and runtime/internal/atomic.
-			ignored := true
-			for _, pos := range pkg.ImportPos[importedPkgPath] {
-				importFile := filepath.Base(pos.Filename)
-				for _, file := range pkg.GoFiles {
-					if importFile == file {
-						ignored = false
-						break
-					}
-				}
-				if !ignored {
-					break
-				}
-			}
-
-			if importedPkgPath == "unsafe" || ignored {
+			if importedPkgPath == "unsafe" {
 				continue
 			}
 			importedPkg, _, err := s.buildImportPathWithSrcDir(importedPkgPath, pkg.Dir)
diff --git a/build/context.go b/build/context.go
@@ -3,6 +3,7 @@ package build
 import (
 	"fmt"
 	"go/build"
+	"go/token"
 	"net/http"
 	"os"
 	"os/exec"
@@ -240,9 +241,14 @@ func (sc simpleCtx) applyPostloadTweaks(pkg *build.Package) *build.Package {
 	case "syscall/js":
 		// Reuse upstream tests to ensure conformance, but completely replace
 		// implementation.
-		pkg.XTestGoFiles = append(pkg.TestGoFiles, "js_test.go")
+		pkg.GoFiles = []string{}
+		pkg.XTestGoFiles = append(pkg.XTestGoFiles, "js_test.go")
 	}
 
+	pkg.Imports, pkg.ImportPos = updateImports(pkg.GoFiles, pkg.ImportPos)
+	pkg.TestImports, pkg.TestImportPos = updateImports(pkg.TestGoFiles, pkg.TestImportPos)
+	pkg.XTestImports, pkg.XTestImportPos = updateImports(pkg.XTestGoFiles, pkg.XTestImportPos)
+
 	return pkg
 }
 
@@ -389,3 +395,31 @@ func IsPkgNotFound(err error) bool {
 		(strings.Contains(err.Error(), "cannot find package") || // Modules off.
 			strings.Contains(err.Error(), "is not in GOROOT")) // Modules on.
 }
+
+// updateImports package's list of import paths to only those present in sources
+// after post-load tweaks.
+func updateImports(sources []string, importPos map[string][]token.Position) (newImports []string, newImportPos map[string][]token.Position) {
+	if importPos == nil {
+		// Short-circuit for tests when no imports are loaded.
+		return nil, nil
+	}
+	sourceSet := map[string]bool{}
+	for _, source := range sources {
+		sourceSet[source] = true
+	}
+
+	newImportPos = map[string][]token.Position{}
+	for importPath, positions := range importPos {
+		for _, pos := range positions {
+			if sourceSet[filepath.Base(pos.Filename)] {
+				newImportPos[importPath] = append(newImportPos[importPath], pos)
+			}
+		}
+	}
+
+	for importPath := range newImportPos {
+		newImports = append(newImports, importPath)
+	}
+	sort.Strings(newImports)
+	return newImports, newImportPos
+}
