add support for multiple requirement input files

Revise dependency_resolver.py to use `click`
Avoid mutating `sys.argv`

Co-authored-by: Logan Pulley <lpulley@ocient.com>

Author: cj81499

python/pip_install/requirements.bzl

@@ -53,7 +53,7 @@ def compile_pip_requirements(
         generate_hashes: whether to put hashes in the requirements_txt file.
         py_binary: the py_binary rule to be used.
         py_test: the py_test rule to be used.
-        requirements_in: file expressing desired dependencies.
+        requirements_in: file(s) expressing desired dependencies.
         requirements_txt: result of "compiling" the requirements.in file.
         requirements_linux: File of linux specific resolve output to check validate if requirement.in has changes.
         requirements_darwin: File of darwin specific resolve output to check validate if requirement.in has changes.
@@ -74,16 +74,17 @@ def compile_pip_requirements(
         visibility = visibility,
     )
 
-    data = [name, requirements_in, requirements_txt] + [f for f in (requirements_linux, requirements_darwin, requirements_windows) if f != None]
+    if type(requirements_in) == "string":
+        requirements_in = [requirements_in]
+    data = [name] + requirements_in + [requirements_txt] + [f for f in (requirements_linux, requirements_darwin, requirements_windows) if f != None]
 
     # Use the Label constructor so this is expanded in the context of the file
     # where it appears, which is to say, in @rules_python
     pip_compile = Label("//python/pip_install/tools/dependency_resolver:dependency_resolver.py")
 
     loc = "$(rlocationpath {})"
 
-    args = [
-        loc.format(requirements_in),
+    args = ["--in={}".format(loc.format(f)) for f in requirements_in] + [
         loc.format(requirements_txt),
         "//%s:%s.update" % (native.package_name(), name),
         "--resolver=backtracking",

python/pip_install/tools/dependency_resolver/dependency_resolver.py

@@ -80,15 +80,15 @@ def _locate(bazel_runfiles, file):
 
 
 @click.command(context_settings={"ignore_unknown_options": True})
-@click.argument("requirements_in")
+@click.option("--in", "requirements_ins", multiple=True, required=True)
 @click.argument("requirements_txt")
 @click.argument("update_target_label")
 @click.option("--requirements-linux")
 @click.option("--requirements-darwin")
 @click.option("--requirements-windows")
 @click.argument("extra_args", nargs=-1, type=click.UNPROCESSED)
 def main(
-    requirements_in: str,
+    requirements_ins: Tuple[str, ...],
     requirements_txt: str,
     update_target_label: str,
     requirements_linux: Optional[str],
@@ -103,7 +103,7 @@ def main(
         requirements_darwin=requirements_darwin, requirements_windows=requirements_windows
     )
 
-    resolved_requirements_in = _locate(bazel_runfiles, requirements_in)
+    resolved_requirements_ins = [_locate(bazel_runfiles, f) for f in requirements_ins]
     resolved_requirements_file = _locate(bazel_runfiles, requirements_file)
 
     # Files in the runfiles directory has the following naming schema:
@@ -120,8 +120,8 @@ def main(
     # use the runfiles file first. Thus, we need to compute the relative path
     # from the execution root.
     # Note: Windows cannot reference generated files without runfiles support enabled.
-    requirements_in_relative = requirements_in[len(repository_prefix):]
-    requirements_file_relative = requirements_file[len(repository_prefix):]
+    requirements_ins_relative = [f[len(repository_prefix) :] for f in requirements_ins]
+    requirements_file_relative = requirements_file[len(repository_prefix) :]
 
     # Before loading click, set the locale for its parser.
     # If it leaks through to the system setting, it may fail:
@@ -158,10 +158,15 @@ def main(
     os.environ["PIP_CONFIG_FILE"] = os.getenv("PIP_CONFIG_FILE") or os.devnull
 
     argv.append(f"--output-file={requirements_file_relative if UPDATE else requirements_out}")
-    argv.append(
-        requirements_in_relative
-        if Path(requirements_in_relative).exists()
-        else resolved_requirements_in
+    argv.extend(
+        (
+            requirements_in_relative
+            if Path(requirements_in_relative).exists()
+            else resolved_requirements_in
+        )
+        for requirements_in_relative, resolved_requirements_in
+        in zip(requirements_ins_relative, resolved_requirements_ins)
+
     )
     argv.extend(extra_args)
 
@@ -196,7 +201,7 @@ def main(
                 print(
                     "pip-compile exited with code 2. This means that pip-compile found "
                     "incompatible requirements or could not find a version that matches "
-                    f"the install requirement in {requirements_in_relative}.",
+                    f"the install requirement in one of {requirements_ins_relative}.",
                     file=sys.stderr,
                 )
                 sys.exit(1)