From bf2fac74f24fa858e18f36029ad6038aa2a4a40b Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Sat, 19 Jan 2019 11:09:23 -0700
Subject: [PATCH] io: use `PWD` to initialize `current-directory`

---
 racket/src/io/file/identity.rkt | 40 ++++++++++++++++++---------------
 racket/src/io/path/system.rkt   | 30 +++++++++++++++++++++++--
 racket/src/racket/src/file.c    |  2 ++
 3 files changed, 52 insertions(+), 20 deletions(-)

diff --git a/racket/src/io/file/identity.rkt b/racket/src/io/file/identity.rkt
index 6bc58f7d26..16add2cd80 100644
--- a/racket/src/io/file/identity.rkt
+++ b/racket/src/io/file/identity.rkt
@@ -11,7 +11,8 @@
                              #:host-path [host-path #f]
                              #:as-link? [as-link? #f] ; used only if `host-path`
                              #:fd [fd #f]
-                             #:port [port #f]) ; for errors, and non-#f if `fd` provided
+                             #:port [port #f] ; for errors, and non-#f if `fd` provided
+                             #:no-error? [no-error? #f])
   (define r0 (if host-path
                  (rktio_path_identity rktio host-path (not as-link?))
                  (rktio_fd_identity rktio fd)))
@@ -21,20 +22,23 @@
                   (rktio_identity_to_vector r0)
                   (rktio_free r0))))
   (end-atomic)
-  (when (rktio-error? r0)
-    (raise-filesystem-error who
-                            r
-                            (if host-path
-                                (format (string-append
-                                         "error obtaining identity for path\n"
-                                         "  path: ~a")
-                                        (host-> host-path))
-                                (format (string-append
-                                         "error obtaining identity for port\n"
-                                         "  port: ~v")
-                                        port))))
-  (+ (vector-ref r 0)
-     (arithmetic-shift (vector-ref r 1)
-                       (vector-ref r 3))
-     (arithmetic-shift (vector-ref r 2)
-                       (+ (vector-ref r 3) (vector-ref r 4)))))
+  (cond
+    [(rktio-error? r0)
+     (and (not no-error?)
+          (raise-filesystem-error who
+                                  r
+                                  (if host-path
+                                      (format (string-append
+                                               "error obtaining identity for path\n"
+                                               "  path: ~a")
+                                              (host-> host-path))
+                                      (format (string-append
+                                               "error obtaining identity for port\n"
+                                               "  port: ~v")
+                                              port))))]
+    [else
+     (+ (vector-ref r 0)
+        (arithmetic-shift (vector-ref r 1)
+                          (vector-ref r 3))
+        (arithmetic-shift (vector-ref r 2)
+                          (+ (vector-ref r 3) (vector-ref r 4))))]))
diff --git a/racket/src/io/path/system.rkt b/racket/src/io/path/system.rkt
index 88820447ba..182b230205 100644
--- a/racket/src/io/path/system.rkt
+++ b/racket/src/io/path/system.rkt
@@ -5,6 +5,8 @@
          "../host/error.rkt"
          "../security/main.rkt"
          "../file/host.rkt"
+         "../envvar/main.rkt"
+         "../file/identity.rkt"
          "path.rkt"
          "parameter.rkt"
          "directory-path.rkt")
@@ -57,8 +59,32 @@
 (define run-file #f)
 (define (set-run-file! p) (set! run-file p))
 
-(define orig-dir (path->directory-path
-                  (host-> (rktio_to_bytes (rktio_get_current_directory rktio)))))
+(define orig-dir
+  (let ()
+    (define os-host-dir (rktio_to_bytes (rktio_get_current_directory rktio)))
+    (define os-dir (path->directory-path (host-> os-host-dir)))
+    (case (system-type 'os)
+      [(windows) os-dir]
+      [else
+       ;; Check `PWD` environment variable, and use it when it
+       ;; refers to the same directory as `os-dir`. That's useful
+       ;; when `PWD` refers to a link, for example.
+       (define pwd (environment-variables-ref (current-environment-variables) #"PWD"))
+       (cond
+         [(not pwd) os-dir]
+         [else
+          (define os-dir-id
+            (begin
+              (start-atomic)
+              (path-or-fd-identity 'original-directory #:host-path os-host-dir #:no-error? #t)))
+          (define pwd-id
+            (begin
+              (start-atomic)
+              (path-or-fd-identity 'original-directory #:host-path pwd #:no-error? #t)))
+          (cond
+            [(and os-dir-id (eqv? os-dir-id pwd-id ))
+             (path->directory-path (host-> pwd))]
+            [else os-dir])])])))
 
 (define collects-dir #f)
 (define (set-collects-dir! p) (set! collects-dir p))
diff --git a/racket/src/racket/src/file.c b/racket/src/racket/src/file.c
index d0f5789ab4..4d3a5bda78 100644
--- a/racket/src/racket/src/file.c
+++ b/racket/src/racket/src/file.c
@@ -1833,6 +1833,8 @@ Scheme_Object *scheme_get_fd_identity(Scheme_Object *port, intptr_t fd, char *pa
   }
 
   if (!ident) {
+    if (noerr)
+      return NULL;
     if (!path) {
       scheme_raise_exn(MZEXN_FAIL_FILESYSTEM,
                        "port-file-identity: error obtaining identity\n"