Add various support for cargo configuration.

Also adds support for parsing and reading configuration options/environment variables from cargo, and allows users to ignore config files in the package.

This adds the `[build.env.cargo-config]` option, which can be set to `complete`, `ignore`, or `default`. If set to `complete`, cross will have access to every to every cargo config file on the host (if using remote cross, a config file is written to a temporary file which is mounted on the data volume at `/.cargo/config.toml`). If set to ignore, any `.cargo/config.toml` files outside of `CARGO_HOME` are ignored, by mounting anonymous data volumes to hide config files in any `.cargo` directories. The default behavior uses the backwards-compatible behavior, allowing cross to access any config files in the package and `CARGO_HOME` directories. If the build is called outside the workspace root or at the workspace root, then we only mount an anonymous volume at `$PWD/.cargo`.

The alias support includes recursive subcommand detection, and errors before it invokes cargo. A sample error message is `[cross] error: alias y has unresolvable recursive definition: x -> y -> z -> a -> y`, and therefore can handle non-trivial recursive subcommands.

.changes/931.json

@@ -1,4 +1,12 @@
-{
-    "description": "deny installation of debian packages that conflict with our cross-compiler toolchains.",
-    "type": "fixed"
-}
+[
+    {
+        "description": "add support for cargo aliases.",
+        "type": "added",
+        "issues": [562],
+    },
+    {
+        "description": "allow users to ignore config files in the package.",
+        "type": "added",
+        "issues": [621]
+    }
+]

.changes/933.json

@@ -0,0 +1,4 @@
+{
+    "description": "deny installation of debian packages that conflict with our cross-compiler toolchains.",
+    "type": "fixed"
+}

docs/cross_toml.md

@@ -21,6 +21,7 @@ For example:
 
 ```toml
 [build.env]
+cargo-config = "complete"
 volumes = ["VOL1_ARG", "VOL2_ARG"]
 passthrough = ["IMPORTANT_ENV_VARIABLES"]
 ```
@@ -63,6 +64,7 @@ This is similar to `build.env`, but allows you to be more specific per target.
 
 ```toml
 [target.x86_64-unknown-linux-gnu.env]
+cargo-config = "ignore"
 volumes = ["VOL1_ARG", "VOL2_ARG"]
 passthrough = ["IMPORTANT_ENV_VARIABLES"]
 ```

src/cargo_config.rs

@@ -0,0 +1,64 @@
+use std::collections::HashMap;
+
+use crate::cargo_toml::CargoToml;
+use crate::config::{split_to_cloned_by_ws, Environment};
+use crate::errors::*;
+
+pub const CARGO_NO_PREFIX_ENVVARS: &[&str] = &[
+    "http_proxy",
+    "TERM",
+    "RUSTDOCFLAGS",
+    "RUSTFLAGS",
+    "BROWSER",
+    "HTTPS_PROXY",
+    "HTTP_TIMEOUT",
+    "https_proxy",
+];
+
+#[derive(Debug)]
+struct CargoEnvironment(Environment);
+
+impl CargoEnvironment {
+    fn new(map: Option<HashMap<&'static str, &'static str>>) -> Self {
+        CargoEnvironment(Environment::new("CARGO", map))
+    }
+
+    pub fn alias(&self, name: &str) -> Option<Vec<String>> {
+        let key = format!("ALIAS_{name}");
+        self.0
+            .get_var(&self.0.var_name(&key))
+            .map(|x| split_to_cloned_by_ws(&x))
+    }
+}
+
+#[derive(Debug)]
+pub struct CargoConfig {
+    toml: Option<CargoToml>,
+    env: CargoEnvironment,
+}
+
+impl CargoConfig {
+    pub fn new(toml: Option<CargoToml>) -> Self {
+        CargoConfig {
+            toml,
+            env: CargoEnvironment::new(None),
+        }
+    }
+
+    pub fn alias(&self, name: &str) -> Result<Option<Vec<String>>> {
+        match self.env.alias(name) {
+            Some(alias) => Ok(Some(alias)),
+            None => match self.toml.as_ref() {
+                Some(t) => t.alias(name),
+                None => Ok(None),
+            },
+        }
+    }
+
+    pub fn to_toml(&self) -> Result<Option<String>> {
+        match self.toml.as_ref() {
+            Some(t) => Ok(Some(t.to_toml()?)),
+            None => Ok(None),
+        }
+    }
+}

src/cargo_toml.rs

@@ -0,0 +1,268 @@
+use std::collections::BTreeSet;
+use std::env;
+use std::path::Path;
+
+use crate::config::split_to_cloned_by_ws;
+use crate::errors::*;
+use crate::file;
+
+type Table = toml::value::Table;
+type Value = toml::value::Value;
+
+// the strategy is to merge, with arrays merging together
+// and the deeper the config file is, the higher its priority.
+// arrays merge, numbers/strings get replaced, objects merge in.
+// we don't want to make any assumptions about the cargo
+// config data, in case we need to use it later.
+#[derive(Debug, Clone, Default)]
+pub struct CargoToml(Table);
+
+impl CargoToml {
+    fn parse(path: &Path) -> Result<CargoToml> {
+        let contents = file::read(&path)
+            .wrap_err_with(|| format!("could not read cargo config file at `{path:?}`"))?;
+        Ok(CargoToml(toml::from_str(&contents)?))
+    }
+
+    pub fn to_toml(&self) -> Result<String> {
+        toml::to_string(&self.0).map_err(Into::into)
+    }
+
+    // finding cargo config files actually runs from the
+    // current working directory the command is invoked,
+    // not from the project root. same is true with work
+    // spaces: the project layout does not matter.
+    pub fn read() -> Result<Option<CargoToml>> {
+        // note: cargo supports both `config` and `config.toml`
+        // `config` exists for compatibility reasons, but if
+        // present, only it will be read.
+        let read = |dir: &Path| -> Result<Option<CargoToml>> {
+            let noext = dir.join("config");
+            let ext = dir.join("config.toml");
+            if noext.exists() {
+                Ok(Some(CargoToml::parse(&noext)?))
+            } else if ext.exists() {
+                Ok(Some(CargoToml::parse(&ext)?))
+            } else {
+                Ok(None)
+            }
+        };
+
+        let read_and_merge = |result: &mut Option<CargoToml>, dir: &Path| -> Result<()> {
+            let parent = read(dir)?;
+            // can't use a match, since there's a use-after-move issue
+            match (result.as_mut(), parent) {
+                (Some(r), Some(p)) => r.merge(&p)?,
+                (None, Some(p)) => *result = Some(p),
+                (Some(_), None) | (None, None) => (),
+            }
+
+            Ok(())
+        };
+
+        let mut result = None;
+        let cwd = env::current_dir()?;
+        let mut dir: &Path = &cwd;
+        loop {
+            read_and_merge(&mut result, &dir.join(".cargo"))?;
+            let parent_dir = dir.parent();
+            match parent_dir {
+                Some(path) => dir = path,
+                None => break,
+            }
+        }
+
+        read_and_merge(&mut result, &home::cargo_home()?)?;
+
+        Ok(result)
+    }
+
+    fn merge(&mut self, parent: &CargoToml) -> Result<()> {
+        // can error on mismatched-data
+
+        fn validate_types(x: &Value, y: &Value) -> Option<()> {
+            match x.same_type(y) {
+                true => Some(()),
+                false => None,
+            }
+        }
+
+        // merge 2 tables. x has precedence over y.
+        fn merge_tables(x: &mut Table, y: &Table) -> Option<()> {
+            // we need to iterate over both keys, so we need a full deduplication
+            let keys: BTreeSet<String> = x.keys().chain(y.keys()).cloned().collect();
+            for key in keys {
+                let in_x = x.contains_key(&key);
+                let in_y = y.contains_key(&key);
+                match (in_x, in_y) {
+                    (true, true) => {
+                        // need to do our merge strategy
+                        let xk = x.get_mut(&key)?;
+                        let yk = y.get(&key)?;
+                        validate_types(xk, yk)?;
+
+                        // now we've filtered out missing keys and optional values
+                        // all key/value pairs should be same type.
+                        if xk.is_table() {
+                            merge_tables(xk.as_table_mut()?, yk.as_table()?)?;
+                        } else if xk.is_array() {
+                            xk.as_array_mut()?.extend_from_slice(yk.as_array()?);
+                        }
+                    }
+                    (false, true) => {
+                        // key in y is not in x: copy it over
+                        let yk = y[&key].clone();
+                        x.insert(key, yk);
+                    }
+                    // key isn't present in y: can ignore it
+                    (_, false) => (),
+                }
+            }
+
+            Some(())
+        }
+
+        merge_tables(&mut self.0, &parent.0).ok_or_else(|| eyre::eyre!("could not merge"))
+    }
+
+    pub fn alias(&self, name: &str) -> Result<Option<Vec<String>>> {
+        let parse_alias = |value: &Value| -> Result<Vec<String>> {
+            if let Some(s) = value.as_str() {
+                Ok(split_to_cloned_by_ws(s))
+            } else if let Some(a) = value.as_array() {
+                a.iter()
+                    .map(|i| {
+                        i.as_str()
+                            .map(ToOwned::to_owned)
+                            .ok_or_else(|| eyre::eyre!("invalid alias type, got {value}"))
+                    })
+                    .collect()
+            } else {
+                eyre::bail!("invalid alias type, got {}", value.type_str());
+            }
+        };
+
+        let alias = match self.0.get("alias") {
+            Some(a) => a,
+            None => return Ok(None),
+        };
+        let table = match alias.as_table() {
+            Some(t) => t,
+            None => eyre::bail!("cargo config aliases must be a table"),
+        };
+
+        match table.get(name) {
+            Some(v) => Ok(Some(parse_alias(v)?)),
+            None => Ok(None),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    macro_rules! s {
+        ($s:literal) => {
+            $s.to_owned()
+        };
+    }
+
+    #[test]
+    fn test_parse() -> Result<()> {
+        let config1 = CargoToml(toml::from_str(CARGO_TOML1)?);
+        let config2 = CargoToml(toml::from_str(CARGO_TOML2)?);
+        assert_eq!(config1.alias("foo")?, Some(vec![s!("build"), s!("foo")]));
+        assert_eq!(config1.alias("bar")?, Some(vec![s!("check"), s!("bar")]));
+        assert_eq!(config2.alias("baz")?, Some(vec![s!("test"), s!("baz")]));
+        assert_eq!(config2.alias("bar")?, Some(vec![s!("init"), s!("bar")]));
+        assert_eq!(config1.alias("far")?, None);
+        assert_eq!(config2.alias("far")?, None);
+
+        let mut merged = config1;
+        merged.merge(&config2)?;
+        assert_eq!(merged.alias("foo")?, Some(vec![s!("build"), s!("foo")]));
+        assert_eq!(merged.alias("baz")?, Some(vec![s!("test"), s!("baz")]));
+        assert_eq!(merged.alias("bar")?, Some(vec![s!("check"), s!("bar")]));
+
+        // check our merge went well, with arrays, etc.
+        assert_eq!(
+            merged
+                .0
+                .get("build")
+                .and_then(|x| x.get("jobs"))
+                .and_then(|x| x.as_integer()),
+            Some(2),
+        );
+        assert_eq!(
+            merged
+                .0
+                .get("build")
+                .and_then(|x| x.get("rustflags"))
+                .and_then(|x| x.as_array())
+                .and_then(|x| x.iter().map(|i| i.as_str()).collect()),
+            Some(vec!["-C lto", "-Zbuild-std", "-Zdoctest-xcompile"]),
+        );
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_read() -> Result<()> {
+        let config = CargoToml::read()?.expect("cross must have cargo config.");
+        assert_eq!(
+            config.alias("build-docker-image")?,
+            Some(vec![s!("xtask"), s!("build-docker-image")])
+        );
+        assert_eq!(
+            config.alias("xtask")?,
+            Some(vec![s!("run"), s!("-p"), s!("xtask"), s!("--")])
+        );
+
+        Ok(())
+    }
+
+    const CARGO_TOML1: &str = r#"
+[alias]
+foo = "build foo"
+bar = "check bar"
+
+[build]
+jobs = 2
+rustc-wrapper = "sccache"
+target = "x86_64-unknown-linux-gnu"
+rustflags = ["-C lto", "-Zbuild-std"]
+incremental = true
+
+[doc]
+browser = "firefox"
+
+[env]
+VAR1 = "VAL1"
+VAR2 = { value = "VAL2", force = true }
+VAR3 = { value = "relative/path", relative = true }
+"#;
+
+    const CARGO_TOML2: &str = r#"
+# want to check tables merge
+# want to check arrays concat
+# want to check rest override
+[alias]
+baz = "test baz"
+bar = "init bar"
+
+[build]
+jobs = 4
+rustc-wrapper = "sccache"
+target = "x86_64-unknown-linux-gnu"
+rustflags = ["-Zdoctest-xcompile"]
+incremental = true
+
+[doc]
+browser = "chromium"
+
+[env]
+VAR1 = "NEW1"
+VAR2 = { value = "VAL2", force = false }
+"#;
+}