feat(internal/pip): implement support for local pip project installations (#6126)

This pull request implements support for installing local Python package
paths via pip.

It is particularly useful for configuring the java installer package to
fetch and build local pip projects such as synthtool directly from
sdk-platform-java/hermetic_build/library_generation without spawning
external remote download calls.

Key Changes:
1. Adds the LocalPath configuration schema field inside config.go and
doc/config-schema.md.
2. Implements LocalPath folder validations and absolute path resolutions
inside internal/pip/pip.go.
3. Integrates local_path configuration inside
internal/librarian/java/librarian.yaml.
4. Updates pip_test.go and install_test.go to pre-create sandboxed paths
and assert correct pip arguments.

For #5154

Author: suztomo

doc/config-schema.md

@@ -78,6 +78,7 @@ This document describes the schema for the librarian.yaml.
 | `name` | string | Is the pip package name. |
 | `version` | string | Is the version to install. |
 | `package` | string | Is the pip install specifier (e.g., "pkg@git+https://..."). |
+| `local_path` | string | Is the path to a local Python package to install. |
 
 ## GoTool Configuration
 

internal/config/config.go

@@ -170,6 +170,9 @@ type PipTool struct {
 
 	// Package is the pip install specifier (e.g., "pkg@git+https://...").
 	Package string `yaml:"package,omitempty"`
+
+	// LocalPath is the path to a local Python package to install.
+	LocalPath string `yaml:"local_path,omitempty"`
 }
 
 // GoTool defines a tool to install via go.

internal/librarian/java/install_test.go

@@ -26,8 +26,13 @@ import (
 
 func TestInstall(t *testing.T) {
 	tmpDir := t.TempDir()
+	t.Chdir(tmpDir)
 	tempHome := t.TempDir()
 	t.Setenv("HOME", tempHome)
+	localPkgDir := filepath.Join(tmpDir, "sdk-platform-java", "hermetic_build", "library_generation")
+	if err := os.MkdirAll(localPkgDir, 0755); err != nil {
+		t.Fatal(err)
+	}
 	m2Repo := filepath.Join(tempHome, ".m2", "repository")
 	gjfDir := filepath.Join(m2Repo, "com", "google", "googlejavaformat", "google-java-format", "1.25.2")
 	if err := os.MkdirAll(gjfDir, 0755); err != nil {
@@ -53,7 +58,7 @@ func TestInstall(t *testing.T) {
 		{
 			name:        "pip",
 			logFilename: "pip_invocations.log",
-			wantArgs:    "pip install PyYAML==6.0.2 jinja2==3.1.6",
+			wantArgs:    "pip install PyYAML==6.0.2 jinja2==3.1.6 " + localPkgDir,
 		},
 		{
 			name:        "mvn",

internal/librarian/java/librarian.yaml

@@ -35,3 +35,5 @@ tools:
       version: "6.0.2"
     - name: jinja2
       version: "3.1.6"
+    - name: synthtool
+      local_path: sdk-platform-java/hermetic_build/library_generation

internal/pip/pip.go

@@ -19,18 +19,36 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 
 	"github.com/googleapis/librarian/internal/command"
 	"github.com/googleapis/librarian/internal/config"
 )
 
-// ErrInstall indicates a failure to install pip packages.
-var ErrInstall = errors.New("failed to install python packages")
+var (
+	// ErrInstall indicates a failure to install pip packages.
+	ErrInstall = errors.New("failed to install python packages")
+
+	// ErrLocalPathNotFound indicates that the specified local package path does not exist.
+	ErrLocalPathNotFound = errors.New("local pip package path not found")
+)
 
 // Install installs a list of pip tools into the environment.
 func Install(ctx context.Context, tools []*config.PipTool) error {
 	var installTargets []string
 	for _, tool := range tools {
+		if tool.LocalPath != "" {
+			absPath, err := filepath.Abs(tool.LocalPath)
+			if err != nil {
+				return fmt.Errorf("failed to resolve absolute path for %s: %w", tool.LocalPath, err)
+			}
+			if _, err := os.Stat(absPath); err != nil {
+				return fmt.Errorf("%w: %w", ErrLocalPathNotFound, err)
+			}
+			installTargets = append(installTargets, absPath)
+			continue
+		}
 		if tool.Package != "" {
 			installTargets = append(installTargets, tool.Package)
 			continue

internal/pip/pip_test.go

@@ -29,7 +29,7 @@ import (
 func TestInstall(t *testing.T) {
 	tmpDir := t.TempDir()
 	stubLogPath := filepath.Join(tmpDir, "pip_invocations.log")
-	stubContent := fmt.Sprintf(`#!/bin/bash
+	stubContent := fmt.Sprintf(`#!/bin/sh
 echo "pip $@" >> %q
 `, stubLogPath)
 	stubDir := filepath.Join(tmpDir, "bin")
@@ -41,6 +41,10 @@ echo "pip $@" >> %q
 		t.Fatal(err)
 	}
 	t.Setenv("PATH", stubDir)
+	localPkgPath := filepath.Join(tmpDir, "mylocalpkg")
+	if err := os.MkdirAll(localPkgPath, 0755); err != nil {
+		t.Fatal(err)
+	}
 	for _, test := range []struct {
 		name     string
 		tools    []*config.PipTool
@@ -68,6 +72,13 @@ echo "pip $@" >> %q
 			},
 			wantArgs: "install requests",
 		},
+		{
+			name: "install local package path",
+			tools: []*config.PipTool{
+				{Name: "synthtool", LocalPath: localPkgPath},
+			},
+			wantArgs: "install " + localPkgPath,
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			_ = os.Remove(stubLogPath)
@@ -95,7 +106,7 @@ func TestInstall_Error(t *testing.T) {
 		t.Fatal(err)
 	}
 	stubPath := filepath.Join(stubDir, "pip")
-	if err := os.WriteFile(stubPath, []byte("#!/bin/bash\nexit 1\n"), 0755); err != nil {
+	if err := os.WriteFile(stubPath, []byte("#!/bin/sh\nexit 1\n"), 0755); err != nil {
 		t.Fatal(err)
 	}
 	for _, test := range []struct {
@@ -114,6 +125,13 @@ func TestInstall_Error(t *testing.T) {
 			},
 			wantErr: ErrInstall,
 		},
+		{
+			name: "local path not found",
+			tools: []*config.PipTool{
+				{Name: "failpkg", LocalPath: filepath.Join(tmpDir, "nonexistentpkg")},
+			},
+			wantErr: ErrLocalPathNotFound,
+		},
 	} {
 		t.Run(test.name, func(t *testing.T) {
 			if test.setup != nil {