Add ResolveDeps for end-to-end dependency resolution

Adds ResolveDeps() which creates a temporary project, adds dependencies
using the managers library (init + add), runs resolution, and parses the
output into a normalized dependency graph.

Also adds Managers() and EcosystemForManager() helpers for discovering
registered parsers.

Author: andrew

go.mod

@@ -4,7 +4,10 @@ go 1.25.7
 
 require github.com/git-pkgs/purl v0.1.8
 
+require gopkg.in/yaml.v3 v3.0.1 // indirect
+
 require (
+	github.com/git-pkgs/managers v0.8.2-0.20260327140953-3ae446558edc
 	github.com/git-pkgs/packageurl-go v0.2.1 // indirect
 	github.com/git-pkgs/vers v0.2.2 // indirect
 )

go.sum

@@ -1,6 +1,12 @@
+github.com/git-pkgs/managers v0.8.2-0.20260327140953-3ae446558edc h1:ps+yFaDqHvvKzgmFCfAJqN5agU4fXiAMsYOJNG6pt3s=
+github.com/git-pkgs/managers v0.8.2-0.20260327140953-3ae446558edc/go.mod h1:8DR7tIQEEyPyJ7QGzStVbovnGl7tAJcrhQLzjQPzFzc=
 github.com/git-pkgs/packageurl-go v0.2.1 h1:j6VnjJiYS9b1nTLfJGsG6SLaA7Nk6Io+ta8grOyTa4o=
 github.com/git-pkgs/packageurl-go v0.2.1/go.mod h1:rcIxiG37BlQLB6FZfgdj9Fm7yjhRQd3l+5o7J0QPAk4=
 github.com/git-pkgs/purl v0.1.8 h1:iyjEHM2WIZUL9A3+q9ylrabqILsN4nOay9X6jfEjmzQ=
 github.com/git-pkgs/purl v0.1.8/go.mod h1:ihlHw3bnSLXat+9Nl9MsJZBYiG7s3NkwmvE3L/Es/sI=
 github.com/git-pkgs/vers v0.2.2 h1:42QkiIURhGN2wM8AuYYU+FbzS1YV6jmdGd1RiFp7gXs=
 github.com/git-pkgs/vers v0.2.2/go.mod h1:biTbSQK1qdbrsxDEKnqe3Jzclxz8vW6uDcwKjfUGcOo=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

resolve_deps.go

@@ -0,0 +1,262 @@
+package resolve
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/git-pkgs/managers"
+	"github.com/git-pkgs/managers/definitions"
+)
+
+// InputDep describes a dependency to add to the generated project.
+type InputDep struct {
+	Name    string // package name in ecosystem-native format
+	Version string // version constraint (optional)
+}
+
+// ErrResolveNotSupported is returned when the manager does not support the resolve operation.
+var ErrResolveNotSupported = errors.New("manager does not support resolve")
+
+// Managers returns the list of manager names that have registered parsers.
+func Managers() []string {
+	names := make([]string, 0, len(parsers))
+	for name := range parsers {
+		names = append(names, name)
+	}
+	return names
+}
+
+// EcosystemForManager returns the ecosystem name for a registered manager.
+func EcosystemForManager(manager string) (string, bool) {
+	eco, ok := managerEcosystem[manager]
+	return eco, ok
+}
+
+// ResolveDeps creates a temporary project, adds the given dependencies using the
+// specified package manager, runs resolution, and parses the output into a
+// dependency graph.
+//
+// The package manager CLI must be installed and available on PATH.
+func ResolveDeps(ctx context.Context, manager string, deps []InputDep) (*Result, error) {
+	// Verify we have a parser for this manager.
+	if _, ok := parsers[manager]; !ok {
+		return nil, fmt.Errorf("%w: %s", ErrUnsupportedManager, manager)
+	}
+
+	// Clear environment variables that might leak from parent processes
+	// (e.g. BUNDLE_GEMFILE from a Rails app calling this binary).
+	clearParentEnv()
+
+	// Create temp directory for the project.
+	tmpDir, err := os.MkdirTemp("", "resolve-*")
+	if err != nil {
+		return nil, fmt.Errorf("creating temp dir: %w", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	// Set up the managers library.
+	defs, err := definitions.LoadEmbedded()
+	if err != nil {
+		return nil, fmt.Errorf("loading manager definitions: %w", err)
+	}
+
+	translator := managers.NewTranslator()
+	runner := managers.NewExecRunner()
+	detector := managers.NewDetector(translator, runner)
+	for _, def := range defs {
+		detector.Register(def)
+	}
+
+	mgr, err := detector.Detect(tmpDir, managers.DetectOptions{Manager: manager})
+	if err != nil {
+		return nil, fmt.Errorf("setting up manager %s: %w", manager, err)
+	}
+
+	// Init the project and add dependencies.
+	if mgr.Supports(managers.CapInit) {
+		result, err := mgr.Init(ctx)
+		if err != nil {
+			return nil, fmt.Errorf("init %s: %w", manager, err)
+		}
+		if !result.Success() {
+			return nil, fmt.Errorf("init %s: exit %d: %s", manager, result.ExitCode, result.Stderr)
+		}
+
+		// Re-detect after init (some commands create subdirectories).
+		mgr, err = detector.Detect(tmpDir, managers.DetectOptions{Manager: manager})
+		if err != nil {
+			return nil, fmt.Errorf("re-detecting manager after init: %w", err)
+		}
+
+		// Add each dependency via the manager CLI.
+		if mgr.Supports(managers.CapAdd) {
+			seen := make(map[string]bool)
+			for _, dep := range deps {
+				if seen[dep.Name] {
+					continue
+				}
+				seen[dep.Name] = true
+
+				result, err := mgr.Add(ctx, dep.Name, managers.AddOptions{Version: dep.Version})
+				if err != nil {
+					return nil, fmt.Errorf("add %s: %w", dep.Name, err)
+				}
+				if !result.Success() {
+					return nil, fmt.Errorf("add %s: exit %d: %s", dep.Name, result.ExitCode, result.Stderr)
+				}
+			}
+		}
+	} else {
+		// Fallback: write a minimal manifest for managers without init.
+		if err := writeManifest(tmpDir, manager, deps); err != nil {
+			return nil, fmt.Errorf("writing manifest for %s: %w", manager, err)
+		}
+
+		// Re-detect so the manager sees the manifest.
+		mgr, err = detector.Detect(tmpDir, managers.DetectOptions{Manager: manager})
+		if err != nil {
+			return nil, fmt.Errorf("detecting manager after manifest write: %w", err)
+		}
+
+		// Run install to resolve dependencies.
+		installResult, err := mgr.Install(ctx, managers.InstallOptions{})
+		if err != nil {
+			return nil, fmt.Errorf("install %s: %w", manager, err)
+		}
+		if !installResult.Success() {
+			return nil, fmt.Errorf("install %s: exit %d: %s", manager, installResult.ExitCode, installResult.Stderr)
+		}
+	}
+
+	// Run resolve to get the dependency graph output.
+	if !mgr.Supports(managers.CapResolve) {
+		return nil, fmt.Errorf("%w: %s", ErrResolveNotSupported, manager)
+	}
+
+	resolveResult, err := mgr.Resolve(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("resolve %s: %w", manager, err)
+	}
+
+	// Parse the output.
+	return Parse(manager, []byte(resolveResult.Stdout))
+}
+
+// writeManifest creates a minimal manifest file for managers that don't support init.
+func writeManifest(dir, manager string, deps []InputDep) error {
+	switch manager {
+	case "pip":
+		return writePipManifest(dir, deps)
+	case "maven":
+		return writeMavenManifest(dir, deps)
+	case "sbt":
+		return writeSbtManifest(dir, deps)
+	default:
+		return fmt.Errorf("no manifest template for manager %s", manager)
+	}
+}
+
+func writePipManifest(dir string, deps []InputDep) error {
+	var lines []string
+	for _, dep := range deps {
+		if dep.Version != "" {
+			lines = append(lines, dep.Name+dep.Version)
+		} else {
+			lines = append(lines, dep.Name)
+		}
+	}
+	return os.WriteFile(filepath.Join(dir, "requirements.txt"), []byte(strings.Join(lines, "\n")+"\n"), 0644)
+}
+
+func writeMavenManifest(dir string, deps []InputDep) error {
+	var depXML strings.Builder
+	for _, dep := range deps {
+		// Maven deps use groupId:artifactId format
+		parts := strings.SplitN(dep.Name, ":", 2)
+		groupID := parts[0]
+		artifactID := groupID
+		if len(parts) == 2 {
+			artifactID = parts[1]
+		}
+		version := dep.Version
+		if version == "" {
+			version = "[0,)"
+		}
+		depXML.WriteString("    <dependency>\n")
+		depXML.WriteString("      <groupId>" + groupID + "</groupId>\n")
+		depXML.WriteString("      <artifactId>" + artifactID + "</artifactId>\n")
+		depXML.WriteString("      <version>" + version + "</version>\n")
+		depXML.WriteString("    </dependency>\n")
+	}
+
+	pom := `<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+  <groupId>resolve</groupId>
+  <artifactId>resolve-tmp</artifactId>
+  <version>0.0.1</version>
+  <dependencies>
+` + depXML.String() + `  </dependencies>
+</project>
+`
+	return os.WriteFile(filepath.Join(dir, "pom.xml"), []byte(pom), 0644)
+}
+
+func writeSbtManifest(dir string, deps []InputDep) error {
+	var lines []string
+	lines = append(lines, `name := "resolve-tmp"`)
+	lines = append(lines, `version := "0.0.1"`)
+	lines = append(lines, "")
+
+	var depLines []string
+	for _, dep := range deps {
+		parts := strings.SplitN(dep.Name, ":", 2)
+		groupID := parts[0]
+		artifactID := groupID
+		if len(parts) == 2 {
+			artifactID = parts[1]
+		}
+		version := dep.Version
+		if version == "" {
+			version = "LATEST"
+		}
+		depLines = append(depLines, fmt.Sprintf(`  "%s" %% "%s" %% "%s"`, groupID, artifactID, version))
+	}
+	if len(depLines) > 0 {
+		lines = append(lines, "libraryDependencies ++= Seq(")
+		lines = append(lines, strings.Join(depLines, ",\n"))
+		lines = append(lines, ")")
+	}
+
+	return os.WriteFile(filepath.Join(dir, "build.sbt"), []byte(strings.Join(lines, "\n")+"\n"), 0644)
+}
+
+// envVarsToClear lists specific environment variables that point to a parent
+// project and would cause package manager commands to operate on the wrong
+// directory (e.g. BUNDLE_GEMFILE from a Rails app).
+var envVarsToClear = []string{
+	"BUNDLE_GEMFILE",
+	"BUNDLE_LOCKFILE",
+	"BUNDLE_BIN_PATH",
+	"BUNDLE_PATH",
+	"BUNDLER_SETUP",
+	"BUNDLER_VERSION",
+	"GEM_HOME",
+	"GEM_PATH",
+	"RUBYOPT",
+	"RUBYLIB",
+}
+
+// clearParentEnv removes environment variables that could interfere with
+// package manager commands run in a temporary directory.
+func clearParentEnv() {
+	for _, key := range envVarsToClear {
+		os.Unsetenv(key)
+	}
+}

resolve_deps_test.go

@@ -0,0 +1,96 @@
+package resolve_test
+
+import (
+	"context"
+	"errors"
+	"os/exec"
+	"testing"
+	"time"
+
+	"github.com/git-pkgs/resolve"
+	_ "github.com/git-pkgs/resolve/parsers"
+)
+
+func hasCommand(name string) bool {
+	_, err := exec.LookPath(name)
+	return err == nil
+}
+
+func TestResolveDepsUnsupportedManager(t *testing.T) {
+	ctx := context.Background()
+	_, err := resolve.ResolveDeps(ctx, "nonexistent", nil)
+	if !errors.Is(err, resolve.ErrUnsupportedManager) {
+		t.Errorf("expected ErrUnsupportedManager, got %v", err)
+	}
+}
+
+func TestResolveDepsNPM(t *testing.T) {
+	if !hasCommand("npm") {
+		t.Skip("npm not installed")
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	result, err := resolve.ResolveDeps(ctx, "npm", []resolve.InputDep{
+		{Name: "express", Version: "4.21.2"},
+	})
+	if err != nil {
+		t.Fatalf("ResolveDeps failed: %v", err)
+	}
+
+	if result.Manager != "npm" {
+		t.Errorf("Manager = %q, want %q", result.Manager, "npm")
+	}
+	if result.Ecosystem != "npm" {
+		t.Errorf("Ecosystem = %q, want %q", result.Ecosystem, "npm")
+	}
+
+	express := findDep(result.Direct, "express")
+	if express == nil {
+		t.Fatal("missing express in results")
+	}
+	if express.Version != "4.21.2" {
+		t.Errorf("express version = %q, want %q", express.Version, "4.21.2")
+	}
+	// express has 30+ transitive deps
+	if len(express.Deps) < 10 {
+		t.Errorf("expected express to have 10+ transitive deps, got %d", len(express.Deps))
+	}
+
+	// spot check a known transitive dep
+	bodyParser := findDep(express.Deps, "body-parser")
+	if bodyParser == nil {
+		t.Fatal("missing body-parser as transitive dep of express")
+	}
+}
+
+func TestResolveDepsManagers(t *testing.T) {
+	names := resolve.Managers()
+	if len(names) == 0 {
+		t.Fatal("expected at least one registered manager")
+	}
+}
+
+func TestResolveDepsEcosystemForManager(t *testing.T) {
+	eco, ok := resolve.EcosystemForManager("npm")
+	if !ok {
+		t.Fatal("expected npm to be registered")
+	}
+	if eco != "npm" {
+		t.Errorf("ecosystem = %q, want %q", eco, "npm")
+	}
+
+	eco, ok = resolve.EcosystemForManager("bundler")
+	if !ok {
+		t.Fatal("expected bundler to be registered")
+	}
+	if eco != "gem" {
+		t.Errorf("ecosystem = %q, want %q", eco, "gem")
+	}
+
+	_, ok = resolve.EcosystemForManager("nonexistent")
+	if ok {
+		t.Error("expected nonexistent manager to not be registered")
+	}
+}