distutils_rust: download vendored crates from LFS

Summary: Switch from dewey to in-repo LFS utility.

Test Plan:
Run `make local` on my Arch Linux. Check `hg-vendored-crates.tar.gz` was
downloaded and stored in `build/`. Run `make local` again and make sure it
says:

  hg-vendored-crates.tar.gz was already downloaded and up-to-date

Reviewers: mbthomas, #mercurial

Reviewed By: mbthomas

Differential Revision: https://phabricator.intern.facebook.com/D6706906

Signature: 6706906:1515723430:233ccbb47286dbc4e5d856ff4b20c848b281928c

distutils_rust/__init__.py

@@ -3,6 +3,7 @@
 # Copyright 2017 Facebook, Inc.
 
 from __future__ import absolute_import
+import contextlib
 import distutils
 import distutils.command.build
 import distutils.core
@@ -13,6 +14,18 @@ import shutil
 import subprocess
 import tarfile
 
+SCRIPT_ROOT = os.path.realpath(os.path.join(__file__, '../..'))
+LFS_SCRIPT_PATH = os.path.join(SCRIPT_ROOT, 'fb/tools/lfs.py')
+
+@contextlib.contextmanager
+def chdir(path):
+    cwd = os.getcwd()
+    try:
+        os.chdir(path)
+        yield
+    finally:
+        os.chdir(cwd)
+
 class RustExtension(object):
     """Data for a Rust extension.
 
@@ -32,25 +45,20 @@ class RustExtension(object):
         self.manifest = manifest or 'Cargo.toml'
 
 class RustVendoredCrates(object):
-    """Data for Rust vendored crates stored in Dewey.
+    """Data for Rust vendored crates stored in LFS.
 
-    'name' is the name of the vendoring set, and is also the Dewey tag.
-
-    'project' is the Dewey project the vendored crates are stored in.
-
-    'hashfile' is the filename that stores the Dewey hash that should be
-    downloaded.
-
-    'path' is the path in Dewey of the file to download.
+    'name' is the name of the vendoring set, and is also the LFS name (with
+    ".tar.gz" appended) to download.
 
     'dest' is the directory into which the archive should be extracted.
     """
-    def __init__(self, name, project=None, hashfile=None, path=None, dest=None):
+    def __init__(self, name, dest=None):
         self.name = name
-        self.project = project
-        self.hashfile = hashfile or '.' + name
-        self.path = path or name + '.tar.gz'
-        self.dest = dest or '.'
+        self.dest = dest or os.getcwd()
+
+    @property
+    def filename(self):
+        return '%s.tar.gz' % self.name
 
 class BuildRustExt(distutils.core.Command):
 
@@ -126,40 +134,21 @@ class BuildRustExt(distutils.core.Command):
         return os.path.join(package_dir, name)
 
     def download_vendored_crates(self, ven):
-        commit = open(ven.hashfile).read()
-        desttarfile = os.path.join(ven.dest, ven.path)
-        desthashfile = desttarfile + ".hash"
-        if (os.path.exists(ven.dest) and
-                os.path.exists(desthashfile) and
-                commit == open(desthashfile).read()):
-            # Already downloaded, nothing to do.
-            return
-
         try:
             os.makedirs(ven.dest)
         except OSError:
             pass
 
         distutils.log.info("downloading vendored crates '%s'", ven.name)
-        cmd = ["dewey", "cat"]
-        if ven.project is not None:
-            cmd += ["--project", ven.project]
-        cmd += [
-            "--commit", commit,
-            "--tag", ven.name,
-            "--path", ven.path,
-            "--dest", desttarfile]
+        cmd = [LFS_SCRIPT_PATH, 'download', ven.filename]
+        with chdir(ven.dest):
+            rc = subprocess.call(cmd)
+            if rc:
+                raise distutils.errors.CompileError(
+                    "download of Rust vendored crates '%s' failed" % ven.name)
 
-        rc = subprocess.call(cmd)
-        if rc:
-            raise distutils.errors.CompileError(
-                "download of Rust vendored crates '%s' failed" % ven.name)
-
-        with tarfile.open(desttarfile, 'r:gz') as tar:
-            tar.extractall(ven.dest)
-        os.remove(desttarfile)
-        with open(desthashfile, 'w') as f:
-            f.write(commit)
+            with tarfile.open(ven.filename, 'r:gz') as tar:
+                tar.extractall(ven.dest)
 
     def build_ext(self, ext):
         distutils.log.info("building '%s' extension", ext.name)

setup.py

@@ -1285,7 +1285,7 @@ def build_libraries(self, libraries):
 distutils.command.build_clib.build_clib.build_libraries = build_libraries
 
 rustvendoredcrates = [
-    RustVendoredCrates('hg-vendored-crates', project='fbsource', dest='build'),
+    RustVendoredCrates('hg-vendored-crates', dest='build'),
 ]
 
 rustextmodules = [