c2a: add option to use Cargo.toml.orig

`Cargo --publish` strips dev-dependencies from Cargo.toml, an issue
that won't be fixed until [1] is resolved, which doesn't seem
likely as it has been open for ~5 years now.

cargo2android needs dev-dependencies listed in Cargo.toml in order
to generate the rust_test in Android.bp, add an option that tells
cargo2android to use the cargo.toml.orig instead of the cargo.toml.

With this change there are now two options that temporarily
update Cargo.toml, so I've pulled these out into a separate class
to clean up the code a bit.

[1] https://github.com/rust-lang/cargo/issues/4242

Test: run against projects with --add_workspace and
--orig-cargo-toml

Change-Id: I3b8633a807c9734981ebde0bef9b73868acf6774

scripts/cargo2android.py

@@ -1320,20 +1320,69 @@ class Runner(object):
         else:
           in_pkg = pkg_section.match(line) is not None
 
+  # Simple class for manipulation and error handling on Cargo.toml files.
+  class CargoToml(object):
+    cargo_toml = './Cargo.toml'
+    cargo_toml_orig = './Cargo.toml.orig'
+    cargo_toml_lines = None
+
+    def __init__(self, args):
+      if not os.access(self.cargo_toml, os.R_OK):
+        print('error: cannot find or read', self.cargo_toml)
+        return None
+
+      if args.orig_cargo_toml:
+        if not os.access(self.cargo_toml_orig, os.R_OK):
+          print('error: cannot find or read', self.cargo_toml_orig)
+          return None
+
+      # These arguments result in modifying the Cargo.toml.
+      # Save the original to be restored.
+      if args.orig_cargo_toml or args.add_workspace:
+        with open(self.cargo_toml, 'r') as in_file:
+          self.cargo_toml_lines = in_file.readlines()
+
+      # Temporarily replace Cargo.toml with Cargo.toml.orig.
+      # This is useful because crates.io removes dev-dependencies from Cargo.toml when
+      # version numbers are not specified, which is not possible for many crates due to
+      # https://github.com/rust-lang/cargo/issues/4242.
+      if args.orig_cargo_toml:
+        with open(self.cargo_toml, 'w') as out_file:
+          with open(self.cargo_toml_orig, 'r') as in_file:
+            lines = in_file.readlines()
+            out_file.writelines(lines)
+        if args.verbose:
+          print('### INFO: Overwrote Cargo.toml with Cargo.toml.orig')
+
+      # Add [workspace] to Cargo.toml if it is not there.
+      if args.add_workspace:
+        with open(self.cargo_toml, 'r') as in_file:
+          lines = in_file.readlines()
+        if '[workspace]\n' in lines:
+          print('### WARNING: found [workspace] in Cargo.toml')
+        else:
+          with open(self.cargo_toml, 'a') as out_file:
+            out_file.write('[workspace]\n')
+            if args.verbose:
+              print('### INFO: added [workspace] to Cargo.toml')
+
+    def restore(self, args):
+      if self.cargo_toml_lines is not None:
+        with open(self.cargo_toml, 'w') as out_file:
+          out_file.writelines(self.cargo_toml_lines)
+        if args.verbose:
+          print('### INFO: restored original Cargo.toml')
+
   def run_cargo(self):
     """Calls cargo -v and save its output to ./cargo.out."""
     if self.skip_cargo:
       return self
-    cargo_toml = './Cargo.toml'
     cargo_out = './cargo.out'
     # Do not use Cargo.lock, because .bp rules are designed to
     # run with "latest" crates avaialable on Android.
     cargo_lock = './Cargo.lock'
     cargo_lock_saved = './cargo.lock.saved'
     had_cargo_lock = os.path.exists(cargo_lock)
-    if not os.access(cargo_toml, os.R_OK):
-      print('ERROR: Cannot find or read', cargo_toml)
-      return self
     if not self.dry_run:
       if os.path.exists(cargo_out):
         os.remove(cargo_out)
@@ -1344,20 +1393,11 @@ class Runner(object):
     # set up search PATH for cargo to find the correct rustc
     saved_path = os.environ['PATH']
     os.environ['PATH'] = os.path.dirname(self.cargo_path) + ':' + saved_path
-    # Add [workspace] to Cargo.toml if it is not there.
+
-    added_workspace = False
+    cargo_toml = self.CargoToml(self.args)
-    if self.args.add_workspace:
+    if cargo_toml is None:
-      with open(cargo_toml, 'r') as in_file:
+      return self
-        cargo_toml_lines = in_file.readlines()
+
-      found_workspace = '[workspace]\n' in cargo_toml_lines
-      if found_workspace:
-        print('### WARNING: found [workspace] in Cargo.toml')
-      else:
-        with open(cargo_toml, 'a') as out_file:
-          out_file.write('[workspace]\n')
-          added_workspace = True
-          if self.args.verbose:
-            print('### INFO: added [workspace] to Cargo.toml')
     for c in self.cargo:
       features = ''
       if c != 'clean':
@@ -1374,11 +1414,9 @@ class Runner(object):
     if self.args.tests:
       cmd = self.cargo_path + ' test' + features + cmd_tail_target + ' -- --list' + cmd_tail_redir
       self.run_cmd(cmd, cargo_out)
-    if added_workspace:  # restore original Cargo.toml
+
-      with open(cargo_toml, 'w') as out_file:
+    cargo_toml.restore(self.args)
-        out_file.writelines(cargo_toml_lines)
+
-      if self.args.verbose:
-        print('### INFO: restored original Cargo.toml')
     os.environ['PATH'] = saved_path
     if not self.dry_run:
       if not had_cargo_lock:  # restore to no Cargo.lock state
@@ -1708,6 +1746,11 @@ def get_parser():
       action='store_true',
       default=False,
       help='skip cargo command, parse cargo.out, and generate Android.bp')
+  parser.add_argument(
+      '--orig-cargo-toml',
+      action='store_true',
+      default=False,
+      help='Use Cargo.toml.orig instead of Cargo.toml.')
   parser.add_argument(
       '--tests',
       action='store_true',