Add dry-run flag and implement AUR support

README.md

@@ -72,6 +72,7 @@ bash          # bash
 |------|-------|-------------|
 | `--state` | `-s` | State file(s) to read package list from (can be used multiple times) |
 | `--yes` | `-y` | Skip confirmation prompts (for scripting) |
+| `--dry-run` | | Simulate sync without making changes |
 | `--help` | `-h` | Show help message |
 
 ### Examples
@@ -114,6 +115,18 @@ sudo declpac --state ~/.config/declpac/base.txt --state ~/.config/declpac/deskto
 cat ~/.config/declpac/full-system.txt | sudo declpac
 ```
 
+#### Dry-Run Preview
+
+```bash
+# Preview what would happen without making changes
+sudo declpac --dry-run --state packages.txt
+
+# Example output:
+# Installed 3 packages, removed 2 packages
+# Would install: vim, git, docker
+# Would remove: python2, perl-xml-parser
+```
+
 ## How It Works
 
 1. **Collect packages** — Reads from all `--state` files and stdin

cmd/declpac/main.go

@@ -17,6 +17,7 @@ import (
 type Config struct {
 	StateFiles []string
 	NoConfirm  bool
+	DryRun     bool
 }
 
 func main() {
@@ -38,6 +39,11 @@ func main() {
 				Usage:       "Skip confirmation prompts",
 				Destination: &cfg.NoConfirm,
 			},
+			&cli.BoolFlag{
+				Name:        "dry-run",
+				Usage:       "Simulate the sync without making changes",
+				Destination: &cfg.DryRun,
+			},
 		},
 		Action: func(ctx context.Context, cmd *cli.Command) error {
 			return run(cfg)
@@ -63,6 +69,16 @@ func run(cfg *Config) error {
 		return err
 	}
 
+	if cfg.DryRun {
+		result, err := pacman.DryRun(merged)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "error: %v\n", err)
+			return err
+		}
+		fmt.Println(output.Format(result))
+		return nil
+	}
+
 	result, err := pacman.Sync(merged)
 	if err != nil {
 		fmt.Fprintf(os.Stderr, "error: %v\n", err)

openspec/changes/declpac-cli-tool/design.md

@@ -77,7 +77,7 @@ package list, with all packages at their latest available versions.
 
 **AUR Integration**
 - First attempt: Try pacman -Syu for all packages (includes AUR auto-install if enabled)
-- For packages not found in pacman repos: Check AUR via Jguer/aur library
+- For packages not found in pacman repos: Batch query AUR via info endpoint (single HTTP request for multiple packages)
 - If package in AUR: Build and install with makepkg (no AUR helpers)
 - AUR packages should also upgrade to latest version (no partial updates)
 - Clone AUR git repo to temp directory
@@ -110,10 +110,12 @@ package list, with all packages at their latest available versions.
 - Multiple --state flags allowed, all additive
 - Stdin input via standard input stream
 - No interactive prompts - fully automated
+- `--dry-run`: Simulate sync without making changes, print what would be installed/removed
 
 **Output Format**
 - Success: Print to stdout: `Installed X packages, removed Y packages`
 - No changes: Print `Installed 0 packages, removed 0 packages`
+- Dry-run: Print `Installed X packages, removed Y packages` with `Would install: ...` and `Would remove: ...` lines
 - Errors: Print error message to stderr
 - Exit codes: 0 for success, 1 for errors
 

openspec/changes/declpac-cli-tool/proposal.md

@@ -19,6 +19,7 @@ list, ensuring all packages are at the latest version.
 - Machine-readable output (install/remove counts, exit codes)
 - No conflict resolution for missing packages (append-only)
 - Print error to stderr for empty state input and exit with code 1
+- Dry-run mode: simulate sync without making changes, show what would be installed/removed
 
 ## Capabilities
 

openspec/changes/declpac-cli-tool/specs/aur-sync/spec.md

@@ -12,7 +12,7 @@ latest versions.
 
 #### Scenario: Fall back to AUR
 - **WHEN** package is not in pacman repositories but is in AUR
-- **THEN** query AUR via Jguer/aur library
+- **THEN** batch query AUR via info endpoint (multiple packages in single request)
 - **AND** build and install with makepkg -si
 
 #### Scenario: Upgrade AUR packages

openspec/changes/declpac-cli-tool/specs/dry-run/spec.md

@@ -0,0 +1,49 @@
+# Dry-Run Mode
+
+## Summary
+
+Add `--dry-run` flag to simulate the sync operation without making any changes
+to the system. Shows what packages would be installed and what would be removed.
+
+## Motivation
+
+Users want to preview the effects of a sync operation before committing changes.
+This is useful for:
+- Verifying the intended changes are correct
+- Avoiding unintended package installations
+- Understanding what orphan cleanup will remove
+
+## Interface
+
+```
+declpac --dry-run --state packages.txt
+```
+
+## Behavior
+
+1. Read state files and stdin (same as normal mode)
+2. Validate packages exist (same as normal mode)
+3. Query current installed packages via `pacman -Qq`
+4. Compare declared packages to current state
+5. Identify packages that would be installed (not currently installed)
+6. Identify orphans that would be removed via `pacman -Qdtq`
+7. Output results with "Would install:" and "Would remove:" sections
+
+## Output Format
+
+```
+Installed 3 packages, removed 2 packages
+Would install: vim, git, docker
+Would remove: python2, perl-xml-parser
+```
+
+## Non-Goals
+
+- Actual package operations (no pacman -Syu, no pacman -Rns execution)
+- Package version comparison
+- Detailed dependency analysis
+
+## Trade-offs
+
+- Doesn't predict transitive dependencies that pacman might install
+- Orphan list may change after packages are installed

openspec/changes/declpac-cli-tool/tasks.md

@@ -93,3 +93,12 @@
 - [x] 10.9 Test AUR fallback with makepkg for AUR package
 - [x] 10.10 Test error handling for missing packages
 - [x] 10.11 Generate final binary
+
+## 11. Dry-Run Mode
+
+- [x] 11.1 Add --dry-run flag to CLI argument parsing
+- [x] 11.2 Implement DryRun function to query current state
+- [x] 11.3 Compare declared packages to current installations
+- [x] 11.4 Identify packages to install (not currently installed)
+- [x] 11.5 Identify orphans to remove via pacman -Qdtq
+- [x] 11.6 Output "Would install:" and "Would remove:" sections

pkg/output/output.go

@@ -1,12 +1,27 @@
 package output
 
-import "fmt"
+import (
+	"fmt"
+	"strings"
+)
 
 type Result struct {
 	Installed int
 	Removed   int
+	ToInstall []string
+	ToRemove  []string
 }
 
 func Format(r *Result) string {
-	return fmt.Sprintf("Installed %d packages, removed %d packages", r.Installed, r.Removed)
+	var b strings.Builder
+	b.WriteString(fmt.Sprintf("Installed %d packages, removed %d packages", r.Installed, r.Removed))
+	if len(r.ToInstall) > 0 {
+		b.WriteString("\nWould install: ")
+		b.WriteString(strings.Join(r.ToInstall, ", "))
+	}
+	if len(r.ToRemove) > 0 {
+		b.WriteString("\nWould remove: ")
+		b.WriteString(strings.Join(r.ToRemove, ", "))
+	}
+	return b.String()
 }

pkg/pacman/pacman.go

@@ -1,7 +1,11 @@
 package pacman
 
 import (
+	"encoding/json"
 	"fmt"
+	"io"
+	"net/http"
+	"net/url"
 	"os"
 	"os/exec"
 	"regexp"
@@ -14,12 +18,15 @@ import (
 var (
 	Root       = "/"
 	LockFile   = "/var/lib/pacman/db.lock"
+	AURInfoURL = "https://aur.archlinux.org/rpc?v=5&type=info"
 )
 
-type Pac struct{}
+type Pac struct {
+	aurCache map[string]AURPackage
+}
 
 func New() (*Pac, error) {
-	return &Pac{}, nil
+	return &Pac{aurCache: make(map[string]AURPackage)}, nil
 }
 
 func (p *Pac) Close() error {
@@ -30,6 +37,18 @@ type PackageInfo struct {
 	Name    string
 	InAUR   bool
 	Exists  bool
+	AURInfo *AURPackage
+}
+
+type AURResponse struct {
+	Results []AURPackage `json:"results"`
+}
+
+type AURPackage struct {
+	Name        string `json:"Name"`
+	PackageBase string `json:"PackageBase"`
+	Version     string `json:"Version"`
+	URL         string `json:"URL"`
 }
 
 func (p *Pac) ValidatePackage(name string) (*PackageInfo, error) {
@@ -43,9 +62,9 @@ func (p *Pac) ValidatePackage(name string) (*PackageInfo, error) {
 		return &PackageInfo{Name: name, Exists: true, InAUR: false}, nil
 	}
 
-	cmd = exec.Command("aur", "search", name)
-	if out, err := cmd.Output(); err == nil && len(out) > 0 {
-		return &PackageInfo{Name: name, Exists: true, InAUR: true}, nil
+	p.ensureAURCache([]string{name})
+	if aurInfo, ok := p.aurCache[name]; ok {
+		return &PackageInfo{Name: name, Exists: true, InAUR: true, AURInfo: &aurInfo}, nil
 	}
 
 	return &PackageInfo{Name: name, Exists: false, InAUR: false}, nil
@@ -105,16 +124,26 @@ func Sync(packages []string) (*output.Result, error) {
 		}
 	}
 
+	pacmanPkgs, aurPkgs := p.categorizePackages(packages)
+
 	for _, pkg := range packages {
 		if err := p.MarkExplicit(pkg); err != nil {
 			fmt.Fprintf(os.Stderr, "warning: could not mark %s as explicit: %v\n", pkg, err)
 		}
 	}
 
-	_, err = p.SyncPackages(packages)
+	if len(pacmanPkgs) > 0 {
+		_, err = p.SyncPackages(pacmanPkgs)
 		if err != nil {
 			return nil, err
 		}
+	}
+
+	for _, pkg := range aurPkgs {
+		if err := p.InstallAUR(pkg); err != nil {
+			return nil, err
+		}
+	}
 
 	removed, err := p.CleanupOrphans()
 	if err != nil {
@@ -130,6 +159,118 @@ func Sync(packages []string) (*output.Result, error) {
 	}, nil
 }
 
+func (p *Pac) categorizePackages(packages []string) (pacmanPkgs, aurPkgs []string) {
+	var notInPacman []string
+
+	for _, pkg := range packages {
+		info, err := p.ValidatePackage(pkg)
+		if err != nil || !info.Exists {
+			notInPacman = append(notInPacman, pkg)
+		} else if !info.InAUR {
+			pacmanPkgs = append(pacmanPkgs, pkg)
+		}
+	}
+
+	if len(notInPacman) > 0 {
+		p.ensureAURCache(notInPacman)
+		for _, pkg := range notInPacman {
+			if _, ok := p.aurCache[pkg]; ok {
+				aurPkgs = append(aurPkgs, pkg)
+			} else {
+				fmt.Fprintf(os.Stderr, "error: package not found: %s\n", pkg)
+			}
+		}
+	}
+
+	return pacmanPkgs, aurPkgs
+}
+
+func (p *Pac) ensureAURCache(packages []string) {
+	if len(packages) == 0 {
+		return
+	}
+
+	var uncached []string
+	for _, pkg := range packages {
+		if _, ok := p.aurCache[pkg]; !ok {
+			uncached = append(uncached, pkg)
+		}
+	}
+
+	if len(uncached) == 0 {
+		return
+	}
+
+	p.fetchAURInfo(uncached)
+}
+
+func (p *Pac) fetchAURInfo(packages []string) map[string]AURPackage {
+	result := make(map[string]AURPackage)
+
+	if len(packages) == 0 {
+		return result
+	}
+
+	v := url.Values{}
+	for _, pkg := range packages {
+		v.Add("arg[]", pkg)
+	}
+
+	resp, err := http.Get(AURInfoURL + "&" + v.Encode())
+	if err != nil {
+		return result
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return result
+	}
+
+	var aurResp AURResponse
+	if err := json.Unmarshal(body, &aurResp); err != nil {
+		return result
+	}
+
+	for _, r := range aurResp.Results {
+		p.aurCache[r.Name] = r
+		result[r.Name] = r
+	}
+
+	return result
+}
+
+func (p *Pac) InstallAUR(pkgName string) error {
+	aurInfo, ok := p.aurCache[pkgName]
+	if !ok {
+		return fmt.Errorf("AUR package not found in cache: %s", pkgName)
+	}
+
+	tmpDir, err := os.MkdirTemp("", "declpac-aur-")
+	if err != nil {
+		return fmt.Errorf("failed to create temp directory: %w", err)
+	}
+	defer os.RemoveAll(tmpDir)
+
+	cloneURL := "https://aur.archlinux.org/" + aurInfo.PackageBase + ".git"
+	cloneCmd := exec.Command("git", "clone", cloneURL, tmpDir)
+	cloneCmd.Stdout = os.Stdout
+	cloneCmd.Stderr = os.Stderr
+	if err := cloneCmd.Run(); err != nil {
+		return fmt.Errorf("failed to clone AUR repo: %w", err)
+	}
+
+	makepkgCmd := exec.Command("makepkg", "-si", "--noconfirm")
+	makepkgCmd.Stdout = os.Stdout
+	makepkgCmd.Stderr = os.Stderr
+	makepkgCmd.Dir = tmpDir
+	if err := makepkgCmd.Run(); err != nil {
+		return fmt.Errorf("makepkg failed to build AUR package: %w", err)
+	}
+
+	return nil
+}
+
 func getInstalledCount() (int, error) {
 	cmd := exec.Command("pacman", "-Qq")
 	output, err := cmd.Output()
@@ -177,3 +318,63 @@ func (p *Pac) CleanupOrphans() (int, error) {
 	count := strings.Count(orphanList, "\n") + 1
 	return count, nil
 }
+
+func DryRun(packages []string) (*output.Result, error) {
+	p, err := New()
+	if err != nil {
+		return nil, err
+	}
+	defer p.Close()
+
+	current, err := p.GetInstalledPackages()
+	if err != nil {
+		return nil, err
+	}
+	currentSet := make(map[string]bool)
+	for _, pkg := range current {
+		currentSet[pkg] = true
+	}
+
+	var toInstall []string
+	var aurPkgs []string
+	for _, pkg := range packages {
+		if !currentSet[pkg] {
+			info, err := p.ValidatePackage(pkg)
+			if err != nil || !info.Exists {
+				return nil, fmt.Errorf("package not found: %s", pkg)
+			}
+			if info.InAUR {
+				aurPkgs = append(aurPkgs, pkg)
+			} else {
+				toInstall = append(toInstall, pkg)
+			}
+		}
+	}
+
+	orphans, err := p.listOrphans()
+	if err != nil {
+		return nil, err
+	}
+
+	return &output.Result{
+		Installed: len(toInstall) + len(aurPkgs),
+		Removed:   len(orphans),
+		ToInstall: append(toInstall, aurPkgs...),
+		ToRemove:  orphans,
+	}, nil
+}
+
+func (p *Pac) listOrphans() ([]string, error) {
+	cmd := exec.Command("pacman", "-Qdtq")
+	orphans, err := cmd.Output()
+	if err != nil {
+		return nil, nil
+	}
+
+	list := strings.TrimSpace(string(orphans))
+	if list == "" {
+		return nil, nil
+	}
+
+	return strings.Split(list, "\n"), nil
+}

pkg/validation/validation.go

@@ -1,8 +1,12 @@
 package validation
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
+	"net/http"
+	"net/url"
 	"os"
 	"os/exec"
 	"time"
@@ -10,6 +14,16 @@ import (
 
 var LockFile = "/var/lib/pacman/db.lock"
 
+const AURInfoURL = "https://aur.archlinux.org/rpc?v=5&type=info"
+
+type AURResponse struct {
+	Results []AURResult `json:"results"`
+}
+
+type AURResult struct {
+	Name string `json:"Name"`
+}
+
 func Validate(packages []string) error {
 	if len(packages) == 0 {
 		return errors.New("no packages found")
@@ -46,29 +60,75 @@ func checkDBFreshness() error {
 }
 
 func validatePackages(packages []string) error {
+	var pacmanPkgs []string
+	var aurPkgs []string
+
 	for _, pkg := range packages {
-		if err := validatePackage(pkg); err != nil {
-			return err
+		if inPacman(pkg) {
+			pacmanPkgs = append(pacmanPkgs, pkg)
+		} else {
+			aurPkgs = append(aurPkgs, pkg)
+		}
+	}
+
+	if len(aurPkgs) > 0 {
+		foundAUR := batchSearchAUR(aurPkgs)
+		for _, pkg := range aurPkgs {
+			if !foundAUR[pkg] {
+				return fmt.Errorf("package not found: %s", pkg)
 			}
 		}
+	}
+
 	return nil
 }
 
-func validatePackage(name string) error {
+func inPacman(name string) bool {
 	cmd := exec.Command("pacman", "-Qip", name)
 	if err := cmd.Run(); err == nil {
-		return nil
+		return true
 	}
 
 	cmd = exec.Command("pacman", "-Sip", name)
 	if err := cmd.Run(); err == nil {
-		return nil
+		return true
 	}
 
-	cmd = exec.Command("aur", "search", name)
-	if out, err := cmd.Output(); err == nil && len(out) > 0 {
-		return nil
+	return false
+}
+
+func batchSearchAUR(packages []string) map[string]bool {
+	result := make(map[string]bool)
+
+	if len(packages) == 0 {
+		return result
+	}
+
+	v := url.Values{}
+	v.Set("type", "info")
+	for _, pkg := range packages {
+		v.Add("arg[]", pkg)
+	}
+
+	resp, err := http.Get(AURInfoURL + "&" + v.Encode())
+	if err != nil {
+		return result
+	}
+	defer resp.Body.Close()
+
+	body, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return result
+	}
+
+	var aurResp AURResponse
+	if err := json.Unmarshal(body, &aurResp); err != nil {
+		return result
+	}
+
+	for _, r := range aurResp.Results {
+		result[r.Name] = true
 	}
 
-	return fmt.Errorf("package not found: %s", name)
+	return result
 }