feat(gazelle): support multiple requirements files in manifest generation (#1301)

For certain workflows it is useful to calculate the integrity hash of
the manifest file based on a number of requirements files. The
requirements locking is usually done by executing a script on each
platform and having gazelle manifest generator be aware that more than
one requirements file may affect the outcome (e.g. the wheels that get
passed to modules map may come from multi_pip_parse rule) is generally
useful.

This change modifies the generation macro to concatenate the
requirements
files into one before passing it to the manifest generator.

examples/build_file_generation/BUILD.bazel

diff --git a/examples/build_file_generation/BUILD.bazel b/examples/build_file_generation/BUILD.bazel
index 7c88d92..928fb12 100644
--- a/examples/build_file_generation/BUILD.bazel
+++ b/examples/build_file_generation/BUILD.bazel
@@ -42,6 +42,8 @@
     name = "gazelle_python_manifest",
     modules_mapping = ":modules_map",
     pip_repository_name = "pip",
+    # NOTE: We can pass a list just like in `bzlmod_build_file_generation` example
+    # but we keep a single target here for regression testing.
     requirements = "//:requirements_lock.txt",
     # NOTE: we can use this flag in order to make our setup compatible with
     # bzlmod.

examples/bzlmod_build_file_generation/BUILD.bazel

diff --git a/examples/bzlmod_build_file_generation/BUILD.bazel b/examples/bzlmod_build_file_generation/BUILD.bazel
index 498969b..c5e27c2 100644
--- a/examples/bzlmod_build_file_generation/BUILD.bazel
+++ b/examples/bzlmod_build_file_generation/BUILD.bazel
@@ -49,7 +49,10 @@
     name = "gazelle_python_manifest",
     modules_mapping = ":modules_map",
     pip_repository_name = "pip",
-    requirements = "//:requirements_lock.txt",
+    requirements = [
+        "//:requirements_lock.txt",
+        "//:requirements_windows.txt",
+    ],
     # NOTE: we can use this flag in order to make our setup compatible with
     # bzlmod.
     use_pip_repository_aliases = True,

examples/bzlmod_build_file_generation/gazelle_python.yaml

diff --git a/examples/bzlmod_build_file_generation/gazelle_python.yaml b/examples/bzlmod_build_file_generation/gazelle_python.yaml
index 12096e5..e33021b 100644
--- a/examples/bzlmod_build_file_generation/gazelle_python.yaml
+++ b/examples/bzlmod_build_file_generation/gazelle_python.yaml
@@ -232,6 +232,7 @@
     isort.wrap: isort
     isort.wrap_modes: isort
     lazy_object_proxy: lazy_object_proxy
+    lazy_object_proxy.cext: lazy_object_proxy
     lazy_object_proxy.compat: lazy_object_proxy
     lazy_object_proxy.simple: lazy_object_proxy
     lazy_object_proxy.slots: lazy_object_proxy
@@ -587,4 +588,4 @@
   pip_repository:
     name: pip
     use_pip_repository_aliases: true
-integrity: d979738b10adbbaff0884837e4414688990491c6c40f6a25d58b9bb564411477
+integrity: cee7684391c4a8a1ff219cd354deae61cdcdee70f2076789aabd5249f3c4eca9

gazelle/manifest/defs.bzl

diff --git a/gazelle/manifest/defs.bzl b/gazelle/manifest/defs.bzl
index 05562a1..f1266a0 100644
--- a/gazelle/manifest/defs.bzl
+++ b/gazelle/manifest/defs.bzl
@@ -30,7 +30,9 @@
 
     Args:
         name: the name used as a base for the targets.
-        requirements: the target for the requirements.txt file.
+        requirements: the target for the requirements.txt file or a list of
+            requirements files that will be concatenated before passing on to
+            the manifest generator.
         pip_repository_name: the name of the pip_install or pip_repository target.
         use_pip_repository_aliases: boolean flag to enable using user-friendly
             python package aliases.
@@ -55,6 +57,16 @@
 
     manifest_generator_hash = Label("//manifest/generate:generate_lib_sources_hash")
 
+    if type(requirements) == "list":
+        native.genrule(
+            name = name + "_requirements_gen",
+            srcs = sorted(requirements),
+            outs = [name + "_requirements.txt"],
+            cmd_bash = "cat $(SRCS) > $@",
+            cmd_bat = "type $(SRCS) > $@",
+        )
+        requirements = name + "_requirements_gen"
+
     update_args = [
         "--manifest-generator-hash",
         "$(rootpath {})".format(manifest_generator_hash),