fix #781: add a "--preserve-symlinks" flag

CHANGELOG.md

@@ -19,6 +19,10 @@
 
     Having a logo for esbuild should make it easier to include esbuild in lists of other tools since the other tools often all have logos.
 
+* Add support for node's `--preserve-symlinks` flag ([#781](https://github.com/evanw/esbuild/issues/781))
+
+    This release adds the `--preserve-symlinks` flag which behaves like [the corresponding flag in node](https://nodejs.org/api/cli.html#cli_preserve_symlinks). Without the flag, esbuild and node will use the real path (after resolving symlinks) as the identity of a file. This means that a given file can only be instantiated once. With the flag, esbuild and node will use the original path (without resolving symlinks) as the identity of a file. This means that a given file can be instantiated multiple times, once for every symlink pointing to it. Each copy will have its own identity so the resulting bundle may contain duplicate files. This option is useful if your code relies on this flag in node (or the [`resolve.symlinks` setting in Webpack](https://webpack.js.org/configuration/resolve/#resolvesymlinks)).
+
 * Ignore a leading byte order mark (BOM) in CSS files ([#776](https://github.com/evanw/esbuild/issues/776))
 
     Some text editors insert a U+FEFF code point at the start of text files. This is a zero-width non-breaking space character. Using one at the start of a file is a convention which is meant to indicate that the contents of the file are UTF-8 encoded. When this is done, the character is called a [byte order mark](https://en.wikipedia.org/wiki/Byte_order_mark).

cmd/esbuild/main.go

@@ -71,6 +71,7 @@ var helpText = func(colors logger.Colors) string {
   --out-extension:.js=.mjs  Use a custom output extension instead of ".js"
   --outbase=...             The base path used to determine entry point output
                             paths (for multiple entry points)
+  --preserve-symlinks       Disable symlink resolution for module lookup
   --public-path=...         Set the base URL for the "file" loader
   --pure:N                  Mark the name N as a pure function for tree shaking
   --resolve-extensions=...  A comma-separated list of implicit extensions

internal/config/config.go

@@ -160,6 +160,7 @@ const (
 
 type Options struct {
 	Mode              Mode
+	PreserveSymlinks  bool
 	RemoveWhitespace  bool
 	MinifyIdentifiers bool
 	MangleSyntax      bool

internal/resolver/resolver.go

@@ -336,13 +336,15 @@ func (r *resolver) finalizeResolve(result ResolveResult) *ResolveResult {
 					result.PreserveUnusedImportsTS = dirInfo.tsConfigJSON.PreserveImportsNotUsedAsValues
 				}
 
-				if entry, ok := dirInfo.entries[base]; ok {
-					if symlink := entry.Symlink(r.fs); symlink != "" {
-						// Is this entry itself a symlink?
-						path.Text = symlink
-					} else if dirInfo.absRealPath != "" {
-						// Is there at least one parent directory with a symlink?
-						path.Text = r.fs.Join(dirInfo.absRealPath, base)
+				if !r.options.PreserveSymlinks {
+					if entry, ok := dirInfo.entries[base]; ok {
+						if symlink := entry.Symlink(r.fs); symlink != "" {
+							// Is this entry itself a symlink?
+							path.Text = symlink
+						} else if dirInfo.absRealPath != "" {
+							// Is there at least one parent directory with a symlink?
+							path.Text = r.fs.Join(dirInfo.absRealPath, base)
+						}
 					}
 				}
 			}
@@ -768,11 +770,13 @@ func (r *resolver) dirInfoUncached(path string) *dirInfo {
 		info.enclosingBrowserScope = parentInfo.enclosingBrowserScope
 
 		// Make sure "absRealPath" is the real path of the directory (resolving any symlinks)
-		if entry, ok := parentInfo.entries[base]; ok {
-			if symlink := entry.Symlink(r.fs); symlink != "" {
-				info.absRealPath = symlink
-			} else if parentInfo.absRealPath != "" {
-				info.absRealPath = r.fs.Join(parentInfo.absRealPath, base)
+		if !r.options.PreserveSymlinks {
+			if entry, ok := parentInfo.entries[base]; ok {
+				if symlink := entry.Symlink(r.fs); symlink != "" {
+					info.absRealPath = symlink
+				} else if parentInfo.absRealPath != "" {
+					info.absRealPath = r.fs.Join(parentInfo.absRealPath, base)
+				}
 			}
 		}
 	}

lib/common.ts

@@ -173,6 +173,7 @@ function flagsForBuildOptions(
   let bundle = getFlag(options, keys, 'bundle', mustBeBoolean);
   let watch = getFlag(options, keys, 'watch', mustBeBooleanOrObject);
   let splitting = getFlag(options, keys, 'splitting', mustBeBoolean);
+  let preserveSymlinks = getFlag(options, keys, 'preserveSymlinks', mustBeBoolean);
   let metafile = getFlag(options, keys, 'metafile', mustBeString);
   let outfile = getFlag(options, keys, 'outfile', mustBeString);
   let outdir = getFlag(options, keys, 'outdir', mustBeString);
@@ -209,6 +210,7 @@ function flagsForBuildOptions(
     }
   }
   if (splitting) flags.push('--splitting');
+  if (preserveSymlinks) flags.push('--preserve-symlinks');
   if (metafile) flags.push(`--metafile=${metafile}`);
   if (outfile) flags.push(`--outfile=${outfile}`);
   if (outdir) flags.push(`--outdir=${outdir}`);

lib/types.ts

@@ -37,6 +37,7 @@ interface CommonOptions {
 export interface BuildOptions extends CommonOptions {
   bundle?: boolean;
   splitting?: boolean;
+  preserveSymlinks?: boolean;
   outfile?: string;
   metafile?: string;
   outdir?: string;

pkg/api/api.go

@@ -244,6 +244,7 @@ type BuildOptions struct {
 
 	GlobalName        string
 	Bundle            bool
+	PreserveSymlinks  bool
 	Splitting         bool
 	Outfile           string
 	Metafile          string

pkg/api/api_impl.go

@@ -616,6 +616,7 @@ func rebuildImpl(
 		AbsNodePaths:          make([]string, len(buildOpts.NodePaths)),
 		Banner:                buildOpts.Banner,
 		Footer:                buildOpts.Footer,
+		PreserveSymlinks:      buildOpts.PreserveSymlinks,
 		WatchMode:             buildOpts.Watch != nil,
 		Plugins:               plugins,
 	}

pkg/cli/cli_impl.go

@@ -38,6 +38,9 @@ func parseOptionsImpl(osArgs []string, buildOpts *api.BuildOptions, transformOpt
 		case arg == "--bundle" && buildOpts != nil:
 			buildOpts.Bundle = true
 
+		case arg == "--preserve-symlinks" && buildOpts != nil:
+			buildOpts.PreserveSymlinks = true
+
 		case arg == "--splitting" && buildOpts != nil:
 			buildOpts.Splitting = true
 

scripts/end-to-end-tests.js

@@ -62,6 +62,7 @@
   // my Windows VM (Windows 10 in VirtualBox on macOS).
   if (process.platform !== 'win32') {
     tests.push(
+      // Without preserve symlinks
       test(['--bundle', 'in.js', '--outfile=node.js'], {
         'in.js': `import {foo} from 'foo'; if (foo !== 123) throw 'fail'`,
         'registry/node_modules/foo/index.js': `export {bar as foo} from 'bar'`,
@@ -87,6 +88,32 @@
         'node_modules/foo/index.js': { symlink: `TEST_DIR_ABS_PATH/registry/node_modules/foo/index.js` },
       }),
 
+      // With preserve symlinks
+      test(['--bundle', 'src/in.js', '--outfile=node.js', '--preserve-symlinks'], {
+        'src/in.js': `import {foo} from 'foo'; if (foo !== 123) throw 'fail'`,
+        'registry/node_modules/foo/index.js': `export {bar as foo} from 'bar'`,
+        'src/node_modules/bar/index.js': `export const bar = 123`,
+        'src/node_modules/foo': { symlink: `../../registry/node_modules/foo` },
+      }),
+      test(['--bundle', 'src/in.js', '--outfile=node.js', '--preserve-symlinks'], {
+        'src/in.js': `import {foo} from 'foo'; if (foo !== 123) throw 'fail'`,
+        'registry/node_modules/foo/index.js': `export {bar as foo} from 'bar'`,
+        'src/node_modules/bar/index.js': `export const bar = 123`,
+        'src/node_modules/foo/index.js': { symlink: `../../../registry/node_modules/foo/index.js` },
+      }),
+      test(['--bundle', 'src/in.js', '--outfile=node.js', '--preserve-symlinks'], {
+        'src/in.js': `import {foo} from 'foo'; if (foo !== 123) throw 'fail'`,
+        'registry/node_modules/foo/index.js': `export {bar as foo} from 'bar'`,
+        'src/node_modules/bar/index.js': `export const bar = 123`,
+        'src/node_modules/foo': { symlink: `TEST_DIR_ABS_PATH/registry/node_modules/foo` },
+      }),
+      test(['--bundle', 'src/in.js', '--outfile=node.js', '--preserve-symlinks'], {
+        'src/in.js': `import {foo} from 'foo'; if (foo !== 123) throw 'fail'`,
+        'registry/node_modules/foo/index.js': `export {bar as foo} from 'bar'`,
+        'src/node_modules/bar/index.js': `export const bar = 123`,
+        'src/node_modules/foo/index.js': { symlink: `TEST_DIR_ABS_PATH/registry/node_modules/foo/index.js` },
+      }),
+
       // This is a test for https://github.com/evanw/esbuild/issues/222
       test(['--bundle', 'src/in.js', '--outfile=out/node.js', '--metafile=out/meta.json', '--platform=node', '--format=cjs'], {
         'a/b/src/in.js': `