Try #684:

CHANGELOG.md

@@ -5,6 +5,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+- #494 - Parse Cargo's --manifest-path option to determine mounted docker root
 - #629 - Update Android NDK version and API version
 - #681 - Warn on unknown fields and confusable targets
 - #665 - when not using [env.volumes](https://github.com/cross-rs/cross#mounting-volumes-into-the-build-environment), mount project in /project

README.md

@@ -355,6 +355,9 @@ $ QEMU_STRACE=1 cross run --target aarch64-unknown-linux-gnu
 - path dependencies (in Cargo.toml) that point outside the Cargo project won't
   work because `cross` use docker containers only mounts the Cargo project so
   the container doesn't have access to the rest of the filesystem.
+  However, you may use Cargo's `--manifest-path` option to reference your
+  target crate, executed from a common root directory from which all your
+  dependencies are available.
 
 ## Minimum Supported Rust Version (MSRV)
 

ci/test.sh

@@ -135,6 +135,21 @@ EOF
                 popd
 
                 rm -rf "${td}"
+                td=$(mktemp -d)
+                git clone \
+                    --depth 1 \
+                    --recursive \
+                    https://github.com/cross-rs/test-workspace "${td}"
+
+                pushd "${td}"
+      cross run --target "${TARGET}" -p binary --manifest-path="./workspace/Cargo.toml"
+                pushd "workspace"
+                cross run --target "${TARGET}" -p binary
+                pushd "binary"
+                cross run --target "${TARGET}"
+                popd
+                popd
+                popd
             ;;
         esac
 

src/cargo.rs

@@ -1,7 +1,8 @@
+use serde::Deserialize;
 use std::path::{Path, PathBuf};
 use std::process::{Command, ExitStatus};
-use std::{env, fs};
 
+use crate::cli::Args;
 use crate::errors::*;
 use crate::extensions::CommandExt;
 
@@ -52,38 +53,96 @@ impl<'a> From<&'a str> for Subcommand {
     }
 }
 
-#[derive(Debug)]
-pub struct Root {
-    path: PathBuf,
+#[derive(Debug, Deserialize)]
+pub struct CargoMetadata {
+    pub workspace_root: PathBuf,
+    pub target_directory: PathBuf,
+    pub packages: Vec<Package>,
+    pub workspace_members: Vec<String>,
 }
 
-impl Root {
-    pub fn path(&self) -> &Path {
-        &self.path
+impl CargoMetadata {
+    fn non_workspace_members(&self) -> impl Iterator<Item = &Package> {
+        self.packages
+            .iter()
+            .filter(|p| !self.workspace_members.iter().any(|m| m == &p.id))
     }
-}
 
-/// Cargo project root
-pub fn root() -> Result<Option<Root>> {
-    let cd = env::current_dir().wrap_err("couldn't get current directory")?;
+    pub fn path_dependencies(&self) -> impl Iterator<Item = &Path> {
+        // TODO: Also filter out things that are in workspace, but not a workspace member
+        self.non_workspace_members().filter_map(|p| p.crate_path())
+    }
+}
 
-    let mut dir = &*cd;
-    loop {
-        let toml = dir.join("Cargo.toml");
+#[derive(Debug, Deserialize)]
+pub struct Package {
+    id: String,
+    manifest_path: PathBuf,
+    source: Option<String>,
+}
 
-        if fs::metadata(&toml).is_ok() {
-            return Ok(Some(Root {
-                path: dir.to_owned(),
-            }));
+impl Package {
+    /// Returns the absolute path to the packages manifest "folder"
+    fn crate_path(&self) -> Option<&Path> {
+        // when source is none, this package is a path dependency or a workspace member
+        if self.source.is_none() {
+            self.manifest_path.parent()
+        } else {
+            None
         }
+    }
+}
 
-        match dir.parent() {
-            Some(p) => dir = p,
-            None => break,
+/// Cargo metadata with specific invocation
+pub fn cargo_metadata_with_args(
+    cd: Option<&Path>,
+    args: Option<&Args>,
+) -> Result<Option<CargoMetadata>> {
+    let mut command = std::process::Command::new(
+        std::env::var("CARGO")
+            .ok()
+            .unwrap_or_else(|| "cargo".to_string()),
+    );
+    command.arg("metadata").arg("--format-version=1");
+    if let Some(cd) = cd {
+        command.current_dir(cd);
+    }
+    if let Some(config) = args {
+        if let Some(ref manifest_path) = config.manifest_path {
+            command.args(["--manifest-path".as_ref(), manifest_path.as_os_str()]);
         }
+    } else {
+        command.arg("--no-deps");
     }
-
-    Ok(None)
+    if let Some(target) = args.and_then(|a| a.target.as_ref()) {
+        command.args(["--filter-platform", target.triple()]);
+    }
+    let output = command.output()?;
+    let manifest: Option<CargoMetadata> =
+        serde_json::from_slice(&output.stdout).wrap_err_with(|| {
+            format!(
+                "{command:?} returned nothing. {:?}",
+                String::from_utf8(output.stderr)
+            )
+        })?;
+    manifest
+        .map(|m| -> Result<_> {
+            Ok(CargoMetadata {
+                target_directory: args
+                    .and_then(|a| a.target_dir.clone())
+                    .map(|p| {
+                        if p.is_relative() {
+                            cd.expect("this is a bug, working directory should be provided here")
+                                .join(p)
+                        } else {
+                            p
+                        }
+                    })
+                    .unwrap_or(m.target_directory),
+                ..m
+            })
+        })
+        .transpose()
 }
 
 /// Pass-through mode

src/cli.rs

@@ -13,11 +13,13 @@ pub struct Args {
     pub target: Option<Target>,
     pub target_dir: Option<PathBuf>,
     pub docker_in_docker: bool,
+    pub manifest_path: Option<PathBuf>,
 }
 
 pub fn parse(target_list: &TargetList) -> Args {
     let mut channel = None;
     let mut target = None;
+    let mut manifest_path: Option<PathBuf> = None;
     let mut target_dir = None;
     let mut sc = None;
     let mut all: Vec<String> = Vec::new();
@@ -28,7 +30,21 @@ pub fn parse(target_list: &TargetList) -> Args {
             if arg.is_empty() {
                 continue;
             }
-            if let ("+", ch) = arg.split_at(1) {
+            if arg == "--manifest-path" {
+                all.push(arg);
+                if let Some(m) = args.next() {
+                    let p = PathBuf::from(&m);
+                    all.push(m);
+                    manifest_path = env::current_dir().ok().map(|cwd| cwd.join(p));
+                }
+            } else if arg.starts_with("--manifest-path=") {
+                manifest_path = arg
+                    .split_once('=')
+                    .map(|x| x.1)
+                    .map(PathBuf::from)
+                    .and_then(|p| env::current_dir().ok().map(|cwd| cwd.join(p)));
+                all.push(arg);
+            } else if let ("+", ch) = arg.split_at(1) {
                 channel = Some(ch.to_string());
             } else if arg == "--target" {
                 all.push(arg);
@@ -73,5 +89,6 @@ pub fn parse(target_list: &TargetList) -> Args {
         target,
         target_dir,
         docker_in_docker,
+        manifest_path,
     }
 }