P2 slice 2: the data root (plan 3.4, 5.5)

ledger_store::root: one private folder for every book, found without the
environment (--root, else the root setup recorded in a file only this
account can write, else the platform default under the home from the
password database). Every folder made 0700, files 0600; a root that is a
link, another user's, open to others, unmarked, or under a folder another
user could swap is refused; no error names it. Setup keeps a recorded
root, never makes a second root or moves books while one holds any, and
leaves a folder holding other things untouched. Books are created and
adopted one at a time; adoption reads the source under its writer lock
(changing nothing in it), copies into staging, re-hashes every stored
file against its name, checks every named file is there, opens and
verifies the copy with the source's head, imports settings for books
that keep none, syncs, and only then renames it into place.
wanderbooks setup makes the root and never prints where it is. Three
review rounds; mutation on the diff (docs/testing.md).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-cli/Cargo.toml

@@ -18,6 +18,7 @@ gui = ["dep:ledger-gui"]
 
 [dependencies]
 ledger-mcp = { path = "../ledger-mcp" }
+ledger-store = { path = "../ledger-store" }
 ledger-gui = { path = "../ledger-gui", optional = true }
 
 [dev-dependencies]

crates/ledger-cli/src/main.rs

@@ -5,6 +5,7 @@
 //! wanderbooks new [DIR] [--codex] [--force] [--no-start]   (alias: init)
 //! wanderbooks gui [DIR | viewer flags]
 //! wanderbooks dev-stdio [server flags]
+//! wanderbooks setup [--root PATH] [--home DIR]
 //! ```
 //!
 //! `wanderbooks` is the one executable (plan D-22): `gui` is the viewer and
@@ -392,10 +393,12 @@ fn print_usage() {
     eprintln!("usage: wanderbooks new [DIR] [--codex] [--force] [--no-start]");
     eprintln!("       wanderbooks gui [DIR | --data-dir PATH ...]");
     eprintln!("       wanderbooks dev-stdio [--data-dir PATH ...]");
+    eprintln!("       wanderbooks setup [--root PATH] [--home DIR]");
     eprintln!();
     eprintln!("  new        make a books directory and start the agent in it (alias: init)");
     eprintln!("  gui        open the live, read-only view of a books directory");
     eprintln!("  dev-stdio  run the books server over stdio (`dev-stdio --help` for its flags)");
+    eprintln!("  setup      make the books' private folder (only your account can open it)");
     eprintln!("  DIR        the books directory (default: current directory)");
     eprintln!("  --force    rewrite the scaffold in an existing books directory");
     eprintln!("  --no-start don't start the agent afterwards");
@@ -795,6 +798,78 @@ fn run_gui(_args: Vec<String>) -> i32 {
     2
 }
 
+/// `wanderbooks setup [--root PATH] [--home DIR]`: make the books'
+/// private folder (plan 3.4): `--root` if given, else
+/// `$XDG_DATA_HOME/wanderbooks`, else the platform's default under the
+/// account's home (`--home`, else the system's user records). The folder's
+/// location is never printed: nothing an agent is shown names it.
+fn run_setup(args: Vec<String>) -> i32 {
+    let mut root: Option<PathBuf> = None;
+    let mut home: Option<PathBuf> = None;
+    let mut args = args.into_iter();
+    while let Some(arg) = args.next() {
+        let slot = match arg.as_str() {
+            "--root" => &mut root,
+            "--home" => &mut home,
+            "--help" | "-h" => {
+                eprintln!("usage: wanderbooks setup [--root PATH] [--home DIR]");
+                eprintln!(
+                    "  --root  where the books' private folder goes (default: your data folder)"
+                );
+                eprintln!("  --home  the account's home (default: from the system's user records)");
+                return 0;
+            }
+            other => {
+                eprintln!("unknown argument: {other}");
+                eprintln!("usage: wanderbooks setup [--root PATH] [--home DIR]");
+                return 2;
+            }
+        };
+        match args.next() {
+            Some(value) => *slot = Some(PathBuf::from(value)),
+            None => {
+                eprintln!("error: {arg} needs a path");
+                return 1;
+            }
+        }
+    }
+    let account = ledger_store::root::account_home().ok();
+    let home = match home.or_else(|| account.clone()) {
+        Some(home) => home,
+        None => {
+            eprintln!("error: {}", ledger_store::root::RootError::NoHome);
+            return 1;
+        }
+    };
+    if account.as_ref() != Some(&home) {
+        eprintln!(
+            "note: --home isn't this account's home, so this account's books server won't \
+             look there (tests and unusual setups only)"
+        );
+    }
+    let xdg = env::var_os("XDG_DATA_HOME").map(PathBuf::from);
+    match ledger_store::root::Root::setup(&home, root.as_deref(), xdg.as_deref()) {
+        Ok((_, report)) => {
+            let what = if report.created {
+                "made"
+            } else if report.tightened {
+                "already there; made private again (other users could open it)"
+            } else {
+                "already there"
+            };
+            println!("The books' private folder: {what}. Only your account can open it.");
+            if report.recorded {
+                println!("It isn't in the default place, so where it is was noted for next time.");
+            }
+            0
+        }
+        Err(e) => {
+            eprintln!("error: {e}");
+            1
+        }
+    }
+}
+
 /// `wanderbooks dev-stdio`: the books server over stdio, in this process.
 fn run_dev_stdio(args: Vec<String>) -> i32 {
     match ledger_mcp::run("wanderbooks dev-stdio", args) {
@@ -815,6 +890,7 @@ fn main() {
     match all.next().as_deref() {
         Some("gui") => std::process::exit(run_gui(all.collect())),
         Some("dev-stdio") => std::process::exit(run_dev_stdio(all.collect())),
+        Some("setup") => std::process::exit(run_setup(all.collect())),
         _ => {}
     }
     let mut dir: Option<PathBuf> = None;
@@ -845,7 +921,7 @@ fn main() {
             }
         }
     }
-    if let Some(mode @ ("gui" | "dev-stdio")) = cmd.as_deref() {
+    if let Some(mode @ ("gui" | "dev-stdio" | "setup")) = cmd.as_deref() {
         eprintln!("`{mode}` must come first: wanderbooks {mode} [its own flags]");
         std::process::exit(2);
     }

crates/ledger-cli/tests/setup.rs

@@ -0,0 +1,124 @@
+//! `wanderbooks setup`: the books' private folder, made from the command
+//! line, with its location never printed.
+#![cfg(unix)]
+
+use std::os::unix::fs::PermissionsExt;
+use std::process::Command;
+
+fn wanderbooks() -> Command {
+    Command::new(env!("CARGO_BIN_EXE_wanderbooks"))
+}
+
+fn mode(path: &std::path::Path) -> u32 {
+    std::fs::metadata(path).unwrap().permissions().mode() & 0o777
+}
+
+#[test]
+fn setup_makes_the_private_folder_and_never_names_it() {
+    let home = tempfile::Builder::new()
+        .prefix("wb-setup-")
+        .tempdir()
+        .unwrap();
+    let root = home.path().join(".local/share/wanderbooks");
+    let out = wanderbooks()
+        .args(["setup", "--home"])
+        .arg(home.path())
+        .env_remove("XDG_DATA_HOME")
+        .output()
+        .unwrap();
+    assert!(out.status.success(), "{out:?}");
+    let text = String::from_utf8_lossy(&out.stdout);
+    assert!(text.contains("The books' private folder: made"), "{text}");
+    assert!(
+        String::from_utf8_lossy(&out.stderr).contains("--home isn't this account's home"),
+        "{out:?}"
+    );
+    assert!(
+        !text.contains(home.path().to_str().unwrap()),
+        "names the folder: {text}"
+    );
+    assert!(!String::from_utf8_lossy(&out.stderr).contains(home.path().to_str().unwrap()));
+    assert_eq!(mode(&root), 0o700);
+    for sub in ["books", "run", "legacy"] {
+        assert_eq!(mode(&root.join(sub)), 0o700, "{sub}");
+    }
+    // Again: already there.
+    let out = wanderbooks()
+        .args(["setup", "--home"])
+        .arg(home.path())
+        .env_remove("XDG_DATA_HOME")
+        .output()
+        .unwrap();
+    assert!(
+        String::from_utf8_lossy(&out.stdout).contains("already there."),
+        "{out:?}"
+    );
+    // Others could open it: made private again.
+    std::fs::set_permissions(&root, std::fs::Permissions::from_mode(0o755)).unwrap();
+    let out = wanderbooks()
+        .args(["setup", "--home"])
+        .arg(home.path())
+        .env_remove("XDG_DATA_HOME")
+        .output()
+        .unwrap();
+    assert!(
+        String::from_utf8_lossy(&out.stdout).contains("made private again"),
+        "{out:?}"
+    );
+    assert_eq!(mode(&root), 0o700);
+}
+
+#[test]
+fn a_root_elsewhere_is_noted_and_xdg_is_honoured() {
+    let home = tempfile::Builder::new()
+        .prefix("wb-setup-xdg-")
+        .tempdir()
+        .unwrap();
+    let xdg = home.path().join("xdg");
+    let out = wanderbooks()
+        .args(["setup", "--home"])
+        .arg(home.path())
+        .env("XDG_DATA_HOME", &xdg)
+        .output()
+        .unwrap();
+    assert!(out.status.success(), "{out:?}");
+    assert!(
+        String::from_utf8_lossy(&out.stdout).contains("noted for next time"),
+        "{out:?}"
+    );
+    assert_eq!(mode(&xdg.join("wanderbooks")), 0o700);
+    let noted =
+        std::fs::read_to_string(home.path().join(".local/share/wanderbooks.location")).unwrap();
+    assert_eq!(
+        noted.trim_end(),
+        xdg.join("wanderbooks").display().to_string()
+    );
+}
+
+#[test]
+fn setup_refuses_what_it_does_not_know_and_unsafe_folders() {
+    let out = wanderbooks().args(["setup", "--bogus"]).output().unwrap();
+    assert_eq!(out.status.code(), Some(2));
+    let out = wanderbooks().args(["setup", "--root"]).output().unwrap();
+    assert_eq!(out.status.code(), Some(1));
+    assert!(String::from_utf8_lossy(&out.stderr).contains("--root needs a path"));
+    let home = tempfile::Builder::new()
+        .prefix("wb-setup-link-")
+        .tempdir()
+        .unwrap();
+    let real = home.path().join("real");
+    std::fs::create_dir(&real).unwrap();
+    std::os::unix::fs::symlink(&real, home.path().join("link")).unwrap();
+    let out = wanderbooks()
+        .args(["setup", "--home"])
+        .arg(home.path())
+        .arg("--root")
+        .arg(home.path().join("link"))
+        .output()
+        .unwrap();
+    assert_eq!(out.status.code(), Some(1), "{out:?}");
+    assert!(String::from_utf8_lossy(&out.stderr).contains("is a symlink"));
+    // A mode comes first.
+    let out = wanderbooks().args(["--force", "setup"]).output().unwrap();
+    assert_eq!(out.status.code(), Some(2));
+}