Adding Augmentor

Author: grantnelson-wf

build/augmentor.go

@@ -0,0 +1,321 @@
+package build
+
+import (
+	"fmt"
+	"go/ast"
+	"go/parser"
+	"go/token"
+	"path"
+	"strconv"
+	"strings"
+
+	"github.com/gopherjs/gopherjs/compiler/astutil"
+)
+
+// overrideInfo is used by parseAndAugment methods to manage
+// directives and how the overlay and original are merged.
+type overrideInfo struct {
+	// KeepOriginal indicates that the original code should be kept
+	// but the identifier will be prefixed by `_gopherjs_original_foo`.
+	// If false the original code is removed.
+	keepOriginal bool
+
+	// purgeMethods indicates that this info is for a type and
+	// if a method has this type as a receiver should also be removed.
+	// If the method is defined in the overlays and therefore has its
+	// own overrides, this will be ignored.
+	purgeMethods bool
+
+	// overrideSignature is the function definition given in the overlays
+	// that should be used to replace the signature in the originals.
+	// Only receivers, type parameters, parameters, and results will be used.
+	overrideSignature *ast.FuncDecl
+}
+
+// pkgOverrideInfo is the collection of overrides still needed for a package.
+type pkgOverrideInfo struct {
+	// overrides is a map of identifier to overrideInfo to override
+	// individual named structs, interfaces, functions, and methods.
+	overrides map[string]overrideInfo
+
+	// overlayFiles are the files from the natives that still haven't been
+	// appended to a file from the package, typically the first file.
+	overlayFiles []*ast.File
+
+	// jsFiles are the additional JS files that are part of the natives.
+	jsFiles []JSFile
+}
+
+// Augmentor is an on-the-fly package augmentor.
+//
+// When a file from a package is being parsed, the Augmentor will augment
+// the AST with the changes loaded from the native overrides.
+// The augmentor will hold onto the override information for additional files
+// that come from the same package. This is designed to be used with
+// `x/tools/go/packages.Load` as a middleware in the parse file step via
+// `Config.ParseFile`.
+//
+// The first file from a package will have any additional methods and
+// information from the natives injected into the AST. All files from a package
+// will be augmented by the overrides.
+type Augmentor struct {
+	// packages is a map of package import path to the package's override.
+	// This is used to keep track of the overrides for a package and indicate
+	// that additional files from the natives have already been applied.
+	packages map[string]*pkgOverrideInfo
+}
+
+func (aug *Augmentor) getPackageOverrides(xctx XContext, pkg *PackageData, fileSet *token.FileSet) *pkgOverrideInfo {
+	importPath := pkg.ImportPath
+	if pkgAug, ok := aug.packages[importPath]; ok {
+		return pkgAug
+	}
+
+	jsFiles, overlayFiles := parseOverlayFiles(xctx, pkg, fileSet)
+
+	overrides := make(map[string]overrideInfo)
+	for _, file := range overlayFiles {
+		augmentOverlayFile(file, overrides)
+	}
+	delete(overrides, `init`)
+
+	pkgAug := &pkgOverrideInfo{
+		overrides:    overrides,
+		overlayFiles: overlayFiles,
+		jsFiles:      jsFiles,
+	}
+
+	if aug.packages == nil {
+		aug.packages = map[string]*pkgOverrideInfo{}
+	}
+	aug.packages[importPath] = pkgAug
+	return pkgAug
+}
+
+func (aug *Augmentor) Augment(xctx XContext, pkg *PackageData, fileSet *token.FileSet, file *ast.File) error {
+	pkgAug := aug.getPackageOverrides(xctx, pkg, fileSet)
+
+	augmentOriginalImports(pkg.ImportPath, file)
+
+	if len(pkgAug.overrides) > 0 {
+		augmentOriginalFile(file, pkgAug.overrides)
+	}
+
+	if len(pkgAug.overlayFiles) > 0 {
+		// Append the overlay files to the first file of the package.
+		// This is to ensure that the package is augmented with all the
+		// additional methods and information from the natives.
+		err := astutil.ConcatenateFiles(file, pkgAug.overlayFiles...)
+		if err != nil {
+			panic(fmt.Errorf("failed to concatenate overlay files onto %q: %w", fileSet.Position(file.Package).Filename, err))
+		}
+		pkgAug.overlayFiles = nil
+	}
+
+	return nil
+}
+
+// parseOverlayFiles loads and parses overlay files
+// to augment the original files with.
+func parseOverlayFiles(xctx XContext, pkg *PackageData, fileSet *token.FileSet) ([]JSFile, []*ast.File) {
+	importPath := pkg.ImportPath
+	isXTest := strings.HasSuffix(importPath, "_test")
+	if isXTest {
+		importPath = importPath[:len(importPath)-5]
+	}
+
+	nativesContext := overlayCtx(xctx.Env())
+	nativesPkg, err := nativesContext.Import(importPath, "", 0)
+	if err != nil {
+		return nil, nil
+	}
+
+	jsFiles := nativesPkg.JSFiles
+	var files []*ast.File
+	names := nativesPkg.GoFiles
+	if pkg.IsTest {
+		names = append(names, nativesPkg.TestGoFiles...)
+	}
+	if isXTest {
+		names = nativesPkg.XTestGoFiles
+	}
+
+	for _, name := range names {
+		fullPath := path.Join(nativesPkg.Dir, name)
+		r, err := nativesContext.bctx.OpenFile(fullPath)
+		if err != nil {
+			panic(err)
+		}
+		// Files should be uniquely named and in the original package directory in order to be
+		// ordered correctly
+		newPath := path.Join(pkg.Dir, "gopherjs__"+name)
+		file, err := parser.ParseFile(fileSet, newPath, r, parser.ParseComments)
+		if err != nil {
+			panic(err)
+		}
+		r.Close()
+
+		files = append(files, file)
+	}
+	return jsFiles, files
+}
+
+// augmentOverlayFile is the part of parseAndAugment that processes
+// an overlay file AST to collect information such as compiler directives
+// and perform any initial augmentation needed to the overlay.
+func augmentOverlayFile(file *ast.File, overrides map[string]overrideInfo) {
+	anyChange := false
+	for i, decl := range file.Decls {
+		purgeDecl := astutil.Purge(decl)
+		switch d := decl.(type) {
+		case *ast.FuncDecl:
+			k := astutil.FuncKey(d)
+			oi := overrideInfo{
+				keepOriginal: astutil.KeepOriginal(d),
+			}
+			if astutil.OverrideSignature(d) {
+				oi.overrideSignature = d
+				purgeDecl = true
+			}
+			overrides[k] = oi
+		case *ast.GenDecl:
+			for j, spec := range d.Specs {
+				purgeSpec := purgeDecl || astutil.Purge(spec)
+				switch s := spec.(type) {
+				case *ast.TypeSpec:
+					overrides[s.Name.Name] = overrideInfo{
+						purgeMethods: purgeSpec,
+					}
+				case *ast.ValueSpec:
+					for _, name := range s.Names {
+						overrides[name.Name] = overrideInfo{}
+					}
+				}
+				if purgeSpec {
+					anyChange = true
+					d.Specs[j] = nil
+				}
+			}
+		}
+		if purgeDecl {
+			anyChange = true
+			file.Decls[i] = nil
+		}
+	}
+	if anyChange {
+		astutil.FinalizeRemovals(file)
+		astutil.PruneImports(file)
+	}
+}
+
+// augmentOriginalImports is the part of parseAndAugment that processes
+// an original file AST to modify the imports for that file.
+func augmentOriginalImports(importPath string, file *ast.File) {
+	switch importPath {
+	case "crypto/rand", "encoding/gob", "encoding/json", "expvar", "go/token", "log", "math/big", "math/rand", "regexp", "time":
+		for _, spec := range file.Imports {
+			path, _ := strconv.Unquote(spec.Path.Value)
+			if path == "sync" {
+				if spec.Name == nil {
+					spec.Name = ast.NewIdent("sync")
+				}
+				spec.Path.Value = `"github.com/gopherjs/gopherjs/nosync"`
+			}
+		}
+	}
+}
+
+// augmentOriginalFile is the part of parseAndAugment that processes an
+// original file AST to augment the source code using the overrides from
+// the overlay files.
+func augmentOriginalFile(file *ast.File, overrides map[string]overrideInfo) {
+	anyChange := false
+	for i, decl := range file.Decls {
+		switch d := decl.(type) {
+		case *ast.FuncDecl:
+			if info, ok := overrides[astutil.FuncKey(d)]; ok {
+				anyChange = true
+				removeFunc := true
+				if info.keepOriginal {
+					// Allow overridden function calls
+					// The standard library implementation of foo() becomes _gopherjs_original_foo()
+					d.Name.Name = "_gopherjs_original_" + d.Name.Name
+					removeFunc = false
+				}
+				if overSig := info.overrideSignature; overSig != nil {
+					d.Recv = overSig.Recv
+					d.Type.TypeParams = overSig.Type.TypeParams
+					d.Type.Params = overSig.Type.Params
+					d.Type.Results = overSig.Type.Results
+					removeFunc = false
+				}
+				if removeFunc {
+					file.Decls[i] = nil
+				}
+			} else if recvKey := astutil.FuncReceiverKey(d); len(recvKey) > 0 {
+				// check if the receiver has been purged, if so, remove the method too.
+				if info, ok := overrides[recvKey]; ok && info.purgeMethods {
+					anyChange = true
+					file.Decls[i] = nil
+				}
+			}
+		case *ast.GenDecl:
+			for j, spec := range d.Specs {
+				switch s := spec.(type) {
+				case *ast.TypeSpec:
+					if _, ok := overrides[s.Name.Name]; ok {
+						anyChange = true
+						d.Specs[j] = nil
+					}
+				case *ast.ValueSpec:
+					if len(s.Names) == len(s.Values) {
+						// multi-value context
+						// e.g. var a, b = 2, foo[int]()
+						// A removal will also remove the value which may be from a
+						// function call. This allows us to remove unwanted statements.
+						// However, if that call has a side effect which still needs
+						// to be run, add the call into the overlay.
+						for k, name := range s.Names {
+							if _, ok := overrides[name.Name]; ok {
+								anyChange = true
+								s.Names[k] = nil
+								s.Values[k] = nil
+							}
+						}
+					} else {
+						// single-value context
+						// e.g. var a, b = foo[int]()
+						// If a removal from the overlays makes all returned values unused,
+						// then remove the function call as well. This allows us to stop
+						// unwanted calls if needed. If that call has a side effect which
+						// still needs to be run, add the call into the overlay.
+						nameRemoved := false
+						for _, name := range s.Names {
+							if _, ok := overrides[name.Name]; ok {
+								nameRemoved = true
+								name.Name = `_`
+							}
+						}
+						if nameRemoved {
+							removeSpec := true
+							for _, name := range s.Names {
+								if name.Name != `_` {
+									removeSpec = false
+									break
+								}
+							}
+							if removeSpec {
+								anyChange = true
+								d.Specs[j] = nil
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+	if anyChange {
+		astutil.FinalizeRemovals(file)
+		astutil.PruneImports(file)
+	}
+}