Add a more comprehensive python deps test (#2675)

Instead of just verifying the versions are valid for an individual
plugin, build a directory structure containing a plugin and its
dependencies and attempt to resolve everything together. This catches
issues like #2674 and also validates the requires-python values. The
requires-python validation caught two issues in mypy plugins at the
latest version.

Author: pkwarren

plugins/community/nipunn1313-mypy-grpc/v5.1.0/buf.plugin.yaml

@@ -11,7 +11,8 @@ registry:
   python:
     package_type: "stub-only"
     # https://github.com/nipunn1313/mypy-protobuf/blob/v5.1.0/pyproject.toml#L21
-    requires_python: ">=3.8"
+    # Bumped to match protobuf requirement.
+    requires_python: ">=3.9"
     deps:
       # https://github.com/nipunn1313/mypy-protobuf/tree/v5.1.0#requirements-to-run-typecheckers-on-stubs-generated-by-mypy-protobuf
       # > Earlier releases might work, but aren't tested.

plugins/community/nipunn1313-mypy/v5.1.0/buf.plugin.yaml

@@ -11,7 +11,8 @@ registry:
   python:
     package_type: "stub-only"
     # https://github.com/nipunn1313/mypy-protobuf/blob/v5.1.0/pyproject.toml#L21
-    requires_python: ">=3.8"
+    # Bumped to match protobuf requirement.
+    requires_python: ">=3.9"
     deps:
       # https://github.com/nipunn1313/mypy-protobuf/tree/v5.1.0#requirements-to-run-typecheckers-on-stubs-generated-by-mypy-protobuf
       # > Earlier releases might work, but aren't tested.

tests/plugins_test.go

@@ -16,6 +16,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"reflect"
+	"slices"
 	"strconv"
 	"strings"
 	"testing"
@@ -59,6 +60,25 @@ plugins:
 	protocGenPluginTemplate = template.Must(template.New("protoc-gen-plugin").Parse(`#!/bin/bash
 
 exec docker run --log-driver=none --rm -i {{.ImageName}}:{{.Version}} "$@"
+`))
+	pyprojectTemplate = template.Must(template.New("pyproject.toml").Parse(`[project]
+name = {{ printf "%q" .Name }}
+version = {{ printf "%q" .Version }}
+{{- if .RequiresPython }}
+requires-python = {{ printf "%q" .RequiresPython }}
+{{- end }}
+dependencies = [
+{{- range .Deps }}
+  {{ printf "%q" . }},
+{{- end }}
+]
+{{- if .Sources }}
+
+[tool.uv.sources]
+{{- range .Sources }}
+{{ .Name }} = { path = {{ printf "%q" .Path }} }
+{{- end }}
+{{- end }}
 `))
 	images = []string{
 		"eliza",
@@ -458,34 +478,93 @@ func cargoReqMatches(req, version string) bool {
 func TestPyPIDependencies(t *testing.T) {
 	t.Parallel()
 	ctx := t.Context()
-	plugins := loadFilteredPlugins(t)
-	for _, p := range plugins {
-		if p.Registry.Python == nil || len(p.Registry.Python.Deps) == 0 {
+	allPlugins := loadAllPlugins(t)
+	pluginByRef := make(map[string]*plugin.Plugin, len(allPlugins))
+	for _, p := range allPlugins {
+		pluginByRef[p.String()] = p
+	}
+	for _, p := range loadFilteredPlugins(t) {
+		if p.Registry.Python == nil {
 			continue
 		}
-		// https://docs.astral.sh/uv/getting-started/installation/
-		_, err := exec.LookPath("uv")
-		require.NoError(t, err, "uv must be installed to run this test")
 		t.Run(fmt.Sprintf("%s/%s@%s", p.Identity.Owner(), p.Identity.Plugin(), p.PluginVersion), func(t *testing.T) {
 			t.Parallel()
+			_, err := exec.LookPath("uv")
+			require.NoError(t, err, "uv must be installed to run this test")
+			// Model every plugin in the dependency closure as its own
+			// distribution, matching how the BSR publishes one SDK package per
+			// plugin. Resolving the graph rather than a flattened list of PyPI
+			// specifiers also verifies that each plugin's requires_python is
+			// compatible with the SDKs it depends on.
 			tmpdir := t.TempDir()
+			writePythonSDKProjects(t, tmpdir, p, pluginByRef, make(map[string]bool))
+			// uv lock resolves the whole graph against PyPI without creating a
+			// virtualenv or installing anything.
+			uvLockCmd := exec.CommandContext(ctx, "uv", "lock")
+			uvLockCmd.Dir = filepath.Join(tmpdir, pythonSDKDirName(p))
+			output, err := uvLockCmd.CombinedOutput()
+			require.NoErrorf(t, err, "uv lock failed - output: %s", string(output))
+		})
+	}
+}
 
-			uvInitCmd := exec.CommandContext(ctx, "uv", "init")
-			uvInitCmd.Dir = tmpdir
-			output, err := uvInitCmd.CombinedOutput()
-			require.NoErrorf(t, err, "uv init failed - output: %s", string(output))
-
-			// Make sure we can add all dependencies with `uv add`, which will lookup
-			// the dependency specifier from pypi and make sure that we can resolve
-			// versions.
-			for _, dep := range p.Registry.Python.Deps {
-				uvInitCmd := exec.CommandContext(ctx, "uv", "add", dep)
-				uvInitCmd.Dir = tmpdir
-				output, err := uvInitCmd.CombinedOutput()
-				require.NoErrorf(t, err, "uv add failed - output: %s", string(output))
-			}
+// pythonSDKDistName returns the distribution name used to model the Python SDK
+// generated by a plugin.
+func pythonSDKDistName(p *plugin.Plugin) string {
+	return p.Identity.Owner() + "-" + p.Identity.Plugin()
+}
+
+// pythonSDKDirName returns the directory holding a plugin's generated pyproject.toml.
+func pythonSDKDirName(p *plugin.Plugin) string {
+	return pythonSDKDistName(p) + "-" + strings.TrimPrefix(p.PluginVersion, "v")
+}
+
+// writePythonSDKProjects writes a pyproject.toml for pythonPlugin and for every
+// plugin in its dependency closure, wiring plugin deps as path dependencies.
+func writePythonSDKProjects(
+	t *testing.T,
+	dir string,
+	pythonPlugin *plugin.Plugin,
+	pluginByRef map[string]*plugin.Plugin,
+	written map[string]bool,
+) {
+	t.Helper()
+	if written[pythonPlugin.String()] {
+		return
+	}
+	written[pythonPlugin.String()] = true
+	type pathSource struct {
+		Name string
+		Path string
+	}
+	deps := slices.Clone(pythonPlugin.Registry.Python.Deps)
+	var sources []pathSource
+	for _, pluginDependency := range pythonPlugin.Deps {
+		pluginDep, ok := pluginByRef[pluginDependency.Plugin]
+		require.Truef(t, ok, "dependency %q of plugin %q not found", pluginDependency.Plugin, pythonPlugin.String())
+		if pluginDep.Registry.Python == nil {
+			continue
+		}
+		deps = append(deps, pythonSDKDistName(pluginDep))
+		sources = append(sources, pathSource{
+			Name: pythonSDKDistName(pluginDep),
+			Path: "../" + pythonSDKDirName(pluginDep),
 		})
+		writePythonSDKProjects(t, dir, pluginDep, pluginByRef, written)
 	}
+	slices.Sort(deps)
+	slices.SortFunc(sources, func(a, b pathSource) int { return cmp.Compare(a.Name, b.Name) })
+	projectDir := filepath.Join(dir, pythonSDKDirName(pythonPlugin))
+	require.NoError(t, os.MkdirAll(projectDir, 0o755))
+	var pyproject bytes.Buffer
+	require.NoError(t, pyprojectTemplate.Execute(&pyproject, map[string]any{
+		"Name":           pythonSDKDistName(pythonPlugin),
+		"Version":        strings.TrimPrefix(pythonPlugin.PluginVersion, "v"),
+		"RequiresPython": pythonPlugin.Registry.Python.RequiresPython,
+		"Deps":           deps,
+		"Sources":        sources,
+	}))
+	require.NoError(t, os.WriteFile(filepath.Join(projectDir, "pyproject.toml"), pyproject.Bytes(), 0o644))
 }
 
 func TestRegistryDepsHaveRegistryConfig(t *testing.T) {