feat(postgres): honor --sandbox-binary for binary discovery

Binary discovery for PostgreSQL was hardcoded to ~/opt/postgresql/<version>
(FindBinary in postgresql.go and basedirFromVersion), so the pg path ignored
the --sandbox-binary flag that the MySQL deploy path already honors.

In deploySandboxPostgreSQL, when --sandbox-binary is explicitly provided, the
binaries are now expected at <sandbox-binary>/<version>/bin/postgres and that
directory is passed to the provider as config.Options["basedir"], which
resolveBasedir already consumes (sandbox.go:150). The basedir then drives
bin/lib/share for initdb and the generated scripts.

The --sandbox-binary flag is shared (default ~/opt/mysql), so it is applied to
PostgreSQL ONLY when flags.Changed() — otherwise the strict historical behavior
(~/opt/postgresql/<version> via FindBinary) is preserved, including the existing
'Run: dbdeployer unpack ...' hint. The Provider interface is unchanged.

Added TestResolveBasedir locking the Options["basedir"] override contract that
the cmd layer now relies on (override honored; empty/absent falls back to
~/opt/postgresql/<version>).

Author: nnosal

cmd/deploy_postgresql.go

@@ -40,7 +40,26 @@ func deploySandboxPostgreSQL(cmd *cobra.Command, args []string) {
 		common.Exitf(1, "invalid version: %s", err)
 	}
 
-	if _, err := p.FindBinary(version); err != nil {
+	// Binary discovery. The --sandbox-binary flag is shared with the MySQL
+	// path and defaults to ~/opt/mysql, so it is only applied to PostgreSQL
+	// when explicitly provided. When set, binaries are expected at
+	// <sandbox-binary>/<version>/bin/postgres and that directory becomes the
+	// sandbox basedir (bin/lib/share). When not set, fall back to the strict
+	// historical behavior: ~/opt/postgresql/<version>.
+	options := map[string]string{}
+	if flags.Changed(globals.SandboxBinaryLabel) {
+		sandboxBinary, _ := flags.GetString(globals.SandboxBinaryLabel)
+		sbAbs, err := common.AbsolutePath(sandboxBinary)
+		if err != nil {
+			common.Exitf(1, "error defining absolute path for --%s: %s", globals.SandboxBinaryLabel, err)
+		}
+		basedir := path.Join(sbAbs, version)
+		binPath := path.Join(basedir, "bin", "postgres")
+		if !common.FileExists(binPath) {
+			common.Exitf(1, "PostgreSQL binary not found at %s", binPath)
+		}
+		options["basedir"] = basedir
+	} else if _, err := p.FindBinary(version); err != nil {
 		common.Exitf(1, "PostgreSQL binaries not found: %s\nRun: dbdeployer unpack --provider=postgresql <server.deb> <client.deb>", err)
 	}
 
@@ -98,7 +117,7 @@ func deploySandboxPostgreSQL(cmd *cobra.Command, args []string) {
 		Host:       "127.0.0.1",
 		DbUser:     dbUser,
 		DbPassword: dbPassword,
-		Options:    map[string]string{},
+		Options:    options,
 	}
 
 	if _, err := p.CreateSandbox(config); err != nil {

providers/postgresql/postgresql_test.go

@@ -1,6 +1,8 @@
 package postgresql
 
 import (
+	"os"
+	"path/filepath"
 	"strings"
 	"testing"
 
@@ -278,3 +280,33 @@ func TestGenerateCheckRecoveryScriptDbUser(t *testing.T) {
 		t.Error("recovery script missing replica ports")
 	}
 }
+
+// TestResolveBasedir locks in the contract that deploy_postgresql.go relies on:
+// an explicit Options["basedir"] override (set when --sandbox-binary is given)
+// is honored as-is, and absent/empty values fall back to ~/opt/postgresql/<ver>.
+func TestResolveBasedir(t *testing.T) {
+	p := NewPostgreSQLProvider()
+	home, _ := os.UserHomeDir()
+	wantDefault := filepath.Join(home, "opt", "postgresql", "18.4")
+
+	// Explicit override is returned verbatim.
+	got, err := p.resolveBasedir(providers.SandboxConfig{
+		Version: "18.4",
+		Options: map[string]string{"basedir": "/custom/root/18.4"},
+	})
+	if err != nil || got != "/custom/root/18.4" {
+		t.Errorf("override: got (%q, %v), want /custom/root/18.4", got, err)
+	}
+
+	// No Options: falls back to ~/opt/postgresql/<version>.
+	got, err = p.resolveBasedir(providers.SandboxConfig{Version: "18.4", Options: map[string]string{}})
+	if err != nil || got != wantDefault {
+		t.Errorf("fallback: got (%q, %v), want %q", got, err, wantDefault)
+	}
+
+	// Empty basedir value is treated as unset (falls back).
+	got, err = p.resolveBasedir(providers.SandboxConfig{Version: "18.4", Options: map[string]string{"basedir": ""}})
+	if err != nil || got != wantDefault {
+		t.Errorf("empty basedir: got (%q, %v), want %q", got, err, wantDefault)
+	}
+}