Refuse incomplete SVG/PDF exports beyond the depth limit (#218)

SVG and PDF exports check the visible subtree's depth before bounds or drawing and refuse, with an actionable message, a document nested past 256 levels instead of silently leaving the deep layers out; nothing partial is written, and an inner layer can still be exported. The CLI and MCP report the same error. Fixes #208.

Also: on Windows, figcraft and figcraft-cli link with an 8 MB main-thread stack (Windows gives 1 MB where Linux and macOS give 8), so an export at the depth limit no longer overflows it.

Co-authored-by: bflatastic <bflatastic@users.noreply.github.com>

apps/figcraft-cli/build.rs

@@ -0,0 +1,14 @@
+//! Windows: give the main thread the stack Linux and macOS give it (see `main_thread_stack`).
+fn main() {
+    main_thread_stack();
+}
+
+/// Windows starts the main thread with 1 MB of stack, Linux and macOS with 8 MB. Layers nest up
+/// to 256 deep in an export, and that recursion needs the same room everywhere.
+fn main_thread_stack() {
+    if std::env::var("CARGO_CFG_TARGET_OS").as_deref() != Ok("windows") {
+        return;
+    }
+    let msvc = std::env::var("CARGO_CFG_TARGET_ENV").as_deref() == Ok("msvc");
+    println!("cargo::rustc-link-arg-bins={}", if msvc { "/STACK:8388608" } else { "-Wl,--stack,8388608" });
+}

apps/figcraft-cli/src/files.rs

@@ -102,8 +102,8 @@ pub fn write_doc(doc: &Document, page: NodeId, out: &str) -> CliResult<()> {
             let v = figcraft_format::to_json(doc).map_err(|e| CliError::Failed(e.to_string()))?;
             serde_json::to_vec_pretty(&v).map_err(|e| CliError::Failed(e.to_string()))?
         }
-        "svg" => figcraft_svg::export_svg(&doc.in_srgb(), &children(doc, page), &Default::default())
-            .ok_or_else(|| CliError::Failed("the page is empty: nothing to export".into()))?
+        "svg" => figcraft_svg::try_export_svg(&doc.in_srgb(), &children(doc, page), &Default::default())
+            .map_err(|e| CliError::Failed(e.to_string()))?
             .into_bytes(),
         "png" | "jpg" | "jpeg" | "webp" => encode(doc, &render_page(doc, page, 1.0)?, &e)?,
         "pdf" => page_pdf(doc, page, &PrintSettings::default())?,
@@ -379,4 +379,31 @@ mod tests {
         assert_eq!(sanitize("../.."), "_");
         assert_eq!(sanitize(""), "layer");
     }
+
+    #[test]
+    fn export_depth_errors_preserve_conversion_destinations() {
+        let mut doc = Document::new("export depth");
+        let page = doc.first_page().unwrap();
+        let root = doc.create(page, figcraft_doc::NodeKind::Frame, "root", 0.0, 0.0, 32.0, 32.0).unwrap();
+        let mut parent = root;
+        for _ in 1..257 {
+            parent = doc.create(parent, figcraft_doc::NodeKind::Group, "group", 0.0, 0.0, 32.0, 32.0).unwrap();
+        }
+        doc.create(parent, figcraft_doc::NodeKind::Rectangle, "leaf", 0.0, 0.0, 8.0, 8.0).unwrap();
+        let stamp = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_nanos();
+        let dir = std::env::temp_dir().join(format!("figcraft-cli-export-depth-{}-{stamp}", std::process::id()));
+        std::fs::create_dir(&dir).unwrap();
+        for ext in ["svg", "pdf"] {
+            let path = dir.join(format!("previous.{ext}"));
+            std::fs::write(&path, b"previous export").unwrap();
+            let CliError::Failed(error) = write_doc(&doc, page, path.to_str().unwrap()).unwrap_err() else {
+                panic!("depth overflow must be an operation failure");
+            };
+            assert!(error.contains("maximum export depth of 256"), "{ext}: {error}");
+            assert!(error.contains("select an inner layer"), "{ext}: {error}");
+            assert_eq!(std::fs::read(&path).unwrap(), b"previous export");
+        }
+        assert_eq!(std::fs::read_dir(&dir).unwrap().count(), 2);
+        std::fs::remove_dir_all(dir).unwrap();
+    }
 }

apps/figcraft-cli/tests/export_depth.rs

@@ -0,0 +1,59 @@
+//! Depth refusal through the actual CLI, including its exit status and destination writes.
+#![allow(clippy::unwrap_used, clippy::expect_used, clippy::panic)]
+
+use figcraft_doc::color::{Color, Paint};
+use figcraft_doc::{Document, NodeKind};
+use std::process::Command;
+
+#[test]
+fn export_depth_cli_refuses_partial_files_and_accepts_an_inner_root() {
+    let mut doc = Document::new("export depth");
+    let root = doc.create(doc.first_page().unwrap(), NodeKind::Frame, "root", 0.0, 0.0, 32.0, 32.0).unwrap();
+    let mut parent = root;
+    for depth in 1..257 {
+        let name = if depth == 1 { "inner-root" } else { "group" };
+        parent = doc.create(parent, NodeKind::Group, name, 0.0, 0.0, 32.0, 32.0).unwrap();
+    }
+    let leaf = doc.create(parent, NodeKind::Rectangle, "leaf", 3.0, 5.0, 13.0, 17.0).unwrap();
+    doc.get_mut(leaf).unwrap().fills = vec![Paint::solid(Color::from_hex("FF0000").unwrap())];
+    let stamp = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).unwrap().as_nanos();
+    let dir = std::env::temp_dir().join(format!("figcraft-cli-depth-process-{}-{stamp}", std::process::id()));
+    std::fs::create_dir(&dir).unwrap();
+    let input = dir.join("deep.figcraft");
+    std::fs::write(&input, figcraft_format::save_bytes(&doc, None).unwrap()).unwrap();
+    for ext in ["svg", "pdf"] {
+        let path = dir.join(format!("previous.{ext}"));
+        std::fs::write(&path, b"previous export").unwrap();
+        for verb in ["convert", "export"] {
+            let mut command = Command::new(env!("CARGO_BIN_EXE_figcraft-cli"));
+            command.arg(verb).arg(&input);
+            if verb == "export" {
+                command.arg("-o");
+            }
+            let output = command.arg(&path).arg("--no-system-fonts").output().unwrap();
+            let error = String::from_utf8_lossy(&output.stderr);
+            assert_eq!(output.status.code(), Some(1), "{verb} {ext}: {error}");
+            assert!(error.contains("maximum export depth of 256"), "{verb} {ext}: {error}");
+            assert!(error.contains("select an inner layer"), "{verb} {ext}: {error}");
+            assert_eq!(std::fs::read(&path).unwrap(), b"previous export");
+        }
+        let inner = dir.join(format!("inner.{ext}"));
+        let output = Command::new(env!("CARGO_BIN_EXE_figcraft-cli"))
+            .arg("export")
+            .arg(&input)
+            .arg("-o")
+            .arg(&inner)
+            .args(["--node", "inner-root", "--no-system-fonts"])
+            .output()
+            .unwrap();
+        assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+        let bytes = std::fs::read(inner).unwrap();
+        if ext == "svg" {
+            assert!(String::from_utf8_lossy(&bytes).contains("#FF0000"));
+        } else {
+            assert!(bytes.starts_with(b"%PDF"));
+        }
+    }
+    assert_eq!(std::fs::read_dir(&dir).unwrap().count(), 5, "no staging files after refusal");
+    std::fs::remove_dir_all(dir).unwrap();
+}