feat: add project-qualified hub labels @hub//project/<stamp>:<pkg>

docs/uv.md

@@ -274,9 +274,10 @@ py_library(
 ## A mental model
 
 ```
-@pypi                                     # Your UV built hub repository
-@pypi//requests:requests                  # The library for a requirement
-@pypi//jinja2-cli/entrypoints:jinja2-cli  # A requirement's declared entrypoint
+@pypi                                        # Your UV built hub repository
+@pypi//requests:requests                     # The library for a requirement
+@pypi//jinja2-cli/entrypoints:jinja2-cli     # A requirement's declared entrypoint
+@pypi//project/my_project:requests           # Project-qualified label (see below)
 ```
 
 This central hub wraps "spoke" internal dependency group repos. For instance if you have two
@@ -286,6 +287,24 @@ over the dependency group targets in which that requirement is defined.
 Hub requirement targets are _incompatible_ with dependency group configurations in which the
 requirement in question is not defined.
 
+### Project-qualified labels
+
+In a multi-project hub where two projects both provide the same package, the unqualified label
+can produce a Bazel "multiple keys match" error when the active dep_group name is shared across
+projects. The project-qualified form scopes the `select()` to a single project, eliminating
+the ambiguity:
+
+```python
+# Unqualified — works unless two projects have the same package + same dep_group name
+deps = ["@pypi//requests"]
+
+# Project-qualified — always routes to exactly one project's resolution
+deps = ["@pypi//project/my_project:requests"]
+```
+
+The `<stamp>` in `//project/<stamp>` is the [PEP 503-normalised](https://peps.python.org/pep-0503/#normalized-names)
+form of the `[project].name` declared in that project's `pyproject.toml`.
+
 Each dependency group requirement is backed by a `whl_install` rule which chooses among
 prebuilt wheels listed in the lockfile to produce the equivalent of a
 `py_library`.

e2e/cases/multi-project-hub/BUILD.bazel

@@ -50,3 +50,32 @@ py_test(
         "@pypi_multi//cowsay",
     ],
 )
+
+# Project-qualified labels: each project exposes its packages under
+# @hub//project/<stamp>:<pkg>, scoping the select to that project only.
+py_test(
+    name = "alpha_qualified",
+    srcs = ["__test__.py"],
+    dep_group = "dev",
+    main = "__test__.py",
+    python_version = "3.11",
+    deps = ["@pypi_multi//project/alpha:cowsay"],
+)
+
+py_test(
+    name = "beta_qualified",
+    srcs = ["__test__.py"],
+    dep_group = "beta",
+    main = "__test__.py",
+    python_version = "3.11",
+    deps = ["@pypi_multi//project/beta:cowsay"],
+)
+
+py_test(
+    name = "gamma_qualified",
+    srcs = ["__test__.py"],
+    dep_group = "gamma",
+    main = "__test__.py",
+    python_version = "3.11",
+    deps = ["@pypi_multi//project/gamma:cowsay"],
+)

e2e/cases/single-project-hub/BUILD.bazel

@@ -14,3 +14,15 @@ py_test(
         "@pypi_single//cowsay",
     ],
 )
+
+# Verifies @hub//project/<stamp>:<pkg> resolves correctly.
+py_test(
+    name = "single_project_hub_qualified_label",
+    srcs = ["__test__.py"],
+    dep_group = "single_project_hub",
+    main = "__test__.py",
+    python_version = "3.11",
+    deps = [
+        "@pypi_single//project/single_project_hub:cowsay",
+    ],
+)

uv/private/uv_hub/repository.bzl

@@ -169,6 +169,56 @@ exports_files(
 
         repository_ctx.file(package_name + "/BUILD.bazel", content = "\n".join(content))
 
+    ################################################################################
+    # Lay down //project/<stamp>/BUILD.bazel — project-qualified labels
+    # (@hub//project/<stamp>:<pkg> scopes the select to one project, avoiding
+    # "multiple keys match" in multi-project hubs with shared package names.)
+    per_project = {}
+    for pkg_name, cfgs in packages.items():
+        for cfg, target in cfgs.items():
+            proj_id = target[1:].split("//")[0]  # "@project__<stamp>//:pkg" → "project__<stamp>"
+            per_project.setdefault(proj_id, {}).setdefault(pkg_name, {})[cfg] = target
+
+    for proj_id, proj_pkgs in sorted(per_project.items()):
+        stamp = proj_id[len("project__"):]
+        proj_cfg_set = {}
+        for pkg_cfgs in proj_pkgs.values():
+            for cfg in pkg_cfgs.keys():
+                proj_cfg_set[cfg] = 1
+        proj_cfg_names = sorted(proj_cfg_set.keys())
+
+        p_content = [
+            """\
+load("@aspect_rules_py//py:defs.bzl", "py_library")
+load("//:defs.bzl", "compatible_with")
+""",
+        ]
+
+        for pkg_name, pkg_cfgs in sorted(proj_pkgs.items()):
+            select_spec = {
+                "//dep_group:{}".format(cfg): tgt
+                for cfg, tgt in pkg_cfgs.items()
+            }
+            p_content.append(
+                """
+alias(
+    name = "{name}",
+    actual = select({select}),
+    target_compatible_with = select(compatible_with({compat})),
+    visibility = ["//visibility:public"],
+)
+""".format(
+                    name = pkg_name,
+                    select = indent(pprint(select_spec), "      ").lstrip(),
+                    compat = repr(proj_cfg_names),
+                ),
+            )
+
+        repository_ctx.file(
+            "project/{}/BUILD.bazel".format(stamp),
+            "\n".join(p_content),
+        )
+
     ################################################################################
     # Lay down //:defs.bzl
     content = [