Set PIP_* env vars for outputs/script (#5368)

* Set PIP_* env vars for outputs/script

* Add test

* add news

conda_build/build.py

@@ -1775,6 +1775,7 @@ def bundle_conda(
         env_output["RECIPE_DIR"] = metadata.path
         env_output["MSYS2_PATH_TYPE"] = "inherit"
         env_output["CHERE_INVOKING"] = "1"
+        _set_env_variables_for_build(metadata, env_output)
         for var in utils.ensure_list(metadata.get_value("build/script_env")):
             if "=" in var:
                 val = var.split("=", 1)[1]
@@ -3060,13 +3061,7 @@ def construct_metadata_for_test(recipedir_or_package, config):
     return m, hash_input
 
 
-def write_build_scripts(m, script, build_file):
-    # TODO: Prepending the prefixes here should probably be guarded by
-    #         if not m.activate_build_script:
-    #       Leaving it as is, for now, since we need a quick, non-disruptive patch release.
-    with utils.path_prepended(m.config.host_prefix, False):
-        with utils.path_prepended(m.config.build_prefix, False):
-            env = environ.get_dict(m=m)
+def _set_env_variables_for_build(m, env):
     env["CONDA_BUILD_STATE"] = "BUILD"
 
     # hard-code this because we never want pip's build isolation
@@ -3098,6 +3093,17 @@ def write_build_scripts(m, script, build_file):
     if "replacements" in env:
         del env["replacements"]
 
+
+def write_build_scripts(m, script, build_file):
+    # TODO: Prepending the prefixes here should probably be guarded by
+    #         if not m.activate_build_script:
+    #       Leaving it as is, for now, since we need a quick, non-disruptive patch release.
+    with utils.path_prepended(m.config.host_prefix, False):
+        with utils.path_prepended(m.config.build_prefix, False):
+            env = environ.get_dict(m=m)
+
+    _set_env_variables_for_build(m, env)
+
     work_file = join(m.config.work_dir, "conda_build.sh")
     env_file = join(m.config.work_dir, "build_env_setup.sh")
     with open(env_file, "w") as bf:

news/5368-pip-outputs

@@ -0,0 +1,19 @@
+### Enhancements
+
+* PIP_* env variables are set when building outputs in multi-output recipes. (#3993 via #5368)
+
+### Bug fixes
+
+* <news item>
+
+### Deprecations
+
+* <news item>
+
+### Docs
+
+* <news item>
+
+### Other
+
+* <news item>

tests/test-recipes/split-packages/script_install_files/subpackage1.py

@@ -2,6 +2,8 @@
 
 out_path = os.path.join(os.environ['PREFIX'], 'subpackage_file_1')
 
+assert "PIP_NO_INDEX" in os.environ
+
 with open(out_path, 'w') as f:
     f.write("weeee")