Add support for [env] section in .cargo/config.toml

src/cargo/core/compiler/compilation.rs

@@ -339,6 +339,16 @@ impl<'cfg> Compilation<'cfg> {
             )
             .env("CARGO_PKG_AUTHORS", &pkg.authors().join(":"))
             .cwd(pkg.root());
+
+        if self.config.cli_unstable().configurable_env {
+            // Apply any environment variables from the config
+            for (key, value) in self.config.env_config()?.iter() {
+                if value.is_force() || cmd.get_env(&key).is_none() {
+                    cmd.env(&key, value.resolve(&self.config));
+                }
+            }
+        }
+
         Ok(cmd)
     }
 }

src/cargo/core/features.rs

@@ -444,6 +444,7 @@ pub struct CliUnstable {
     pub weak_dep_features: bool,
     pub extra_link_arg: bool,
     pub credential_process: bool,
+    pub configurable_env: bool,
 }
 
 const STABILIZED_COMPILE_PROGRESS: &str = "The progress bar is now always \
@@ -598,6 +599,7 @@ impl CliUnstable {
             "doctest-xcompile" => self.doctest_xcompile = parse_empty(k, v)?,
             "panic-abort-tests" => self.panic_abort_tests = parse_empty(k, v)?,
             "jobserver-per-rustc" => self.jobserver_per_rustc = parse_empty(k, v)?,
+            "configurable-env" => self.configurable_env = parse_empty(k, v)?,
             "features" => {
                 // For now this is still allowed (there are still some
                 // unstable options like "compare"). This should be removed at

src/cargo/util/config/mod.rs

@@ -49,10 +49,12 @@
 //! translate from `ConfigValue` and environment variables to the caller's
 //! desired type.
 
+use std::borrow::Cow;
 use std::cell::{RefCell, RefMut};
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::collections::{HashMap, HashSet};
 use std::env;
+use std::ffi::OsStr;
 use std::fmt;
 use std::fs::{self, File};
 use std::io::prelude::*;
@@ -181,6 +183,7 @@ pub struct Config {
     target_cfgs: LazyCell<Vec<(String, TargetCfgConfig)>>,
     doc_extern_map: LazyCell<RustdocExternMap>,
     progress_config: ProgressConfig,
+    env_config: LazyCell<EnvConfig>,
 }
 
 impl Config {
@@ -264,6 +267,7 @@ impl Config {
             target_cfgs: LazyCell::new(),
             doc_extern_map: LazyCell::new(),
             progress_config: ProgressConfig::default(),
+            env_config: LazyCell::new(),
         }
     }
 
@@ -1244,6 +1248,11 @@ impl Config {
         &self.progress_config
     }
 
+    pub fn env_config(&self) -> CargoResult<&EnvConfig> {
+        self.env_config
+            .try_borrow_with(|| self.get::<EnvConfig>("env"))
+    }
+
     /// This is used to validate the `term` table has valid syntax.
     ///
     /// This is necessary because loading the term settings happens very
@@ -1953,6 +1962,54 @@ where
     deserializer.deserialize_option(ProgressVisitor)
 }
 
+#[derive(Debug, Deserialize)]
+#[serde(untagged)]
+enum EnvConfigValueInner {
+    Simple(String),
+    WithOptions {
+        value: String,
+        #[serde(default)]
+        force: bool,
+        #[serde(default)]
+        relative: bool,
+    },
+}
+
+#[derive(Debug, Deserialize)]
+#[serde(transparent)]
+pub struct EnvConfigValue {
+    inner: Value<EnvConfigValueInner>,
+}
+
+impl EnvConfigValue {
+    pub fn is_force(&self) -> bool {
+        match self.inner.val {
+            EnvConfigValueInner::Simple(_) => false,
+            EnvConfigValueInner::WithOptions { force, .. } => force,
+        }
+    }
+
+    pub fn resolve<'a>(&'a self, config: &Config) -> Cow<'a, OsStr> {
+        match self.inner.val {
+            EnvConfigValueInner::Simple(ref s) => Cow::Borrowed(OsStr::new(s.as_str())),
+            EnvConfigValueInner::WithOptions {
+                ref value,
+                relative,
+                ..
+            } => {
+                if relative {
+                    let p = self.inner.definition.root(config).join(&value);
+                    Cow::Owned(p.into_os_string())
+                } else {
+                    Cow::Borrowed(OsStr::new(value.as_str()))
+                }
+            }
+        }
+    }
+}
+
+pub type EnvConfig = HashMap<String, EnvConfigValue>;
+
 /// A type to deserialize a list of strings from a toml file.
 ///
 /// Supports deserializing either a whitespace-separated list of arguments in a

tests/testsuite/cargo_env_config.rs

@@ -0,0 +1,133 @@
+//! Tests for `[env]` config.
+
+use cargo_test_support::{basic_bin_manifest, project};
+
+#[cargo_test]
+fn env_basic() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file(
+            "src/main.rs",
+            r#"
+        use std::env;
+        fn main() {
+            println!( "compile-time:{}", env!("ENV_TEST_1233") );
+            println!( "run-time:{}", env::var("ENV_TEST_1233").unwrap());
+        }
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+                [env]
+                ENV_TEST_1233 = "Hello"
+            "#,
+        )
+        .build();
+
+    p.cargo("run -Zconfigurable-env")
+        .masquerade_as_nightly_cargo()
+        .with_stdout_contains("compile-time:Hello")
+        .with_stdout_contains("run-time:Hello")
+        .run();
+}
+
+#[cargo_test]
+fn env_invalid() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file(
+            "src/main.rs",
+            r#"
+        fn main() {
+        }
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+                [env]
+                ENV_TEST_BOOL = false
+            "#,
+        )
+        .build();
+
+    p.cargo("build -Zconfigurable-env")
+        .masquerade_as_nightly_cargo()
+        .with_status(101)
+        .with_stderr_contains("[..]could not load config key `env.ENV_TEST_BOOL`")
+        .run();
+}
+
+#[cargo_test]
+fn env_force() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo"))
+        .file(
+            "src/main.rs",
+            r#"
+        use std::env;
+        fn main() {
+            println!( "ENV_TEST_FORCED:{}", env!("ENV_TEST_FORCED") );
+            println!( "ENV_TEST_UNFORCED:{}", env!("ENV_TEST_UNFORCED") );
+            println!( "ENV_TEST_UNFORCED_DEFAULT:{}", env!("ENV_TEST_UNFORCED_DEFAULT") );
+        }
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+                [env]
+                ENV_TEST_UNFORCED_DEFAULT = "from-config"
+                ENV_TEST_UNFORCED = { value = "from-config", force = false }
+                ENV_TEST_FORCED = { value = "from-config", force = true }
+            "#,
+        )
+        .build();
+
+    p.cargo("run -Zconfigurable-env")
+        .masquerade_as_nightly_cargo()
+        .env("ENV_TEST_FORCED", "from-env")
+        .env("ENV_TEST_UNFORCED", "from-env")
+        .env("ENV_TEST_UNFORCED_DEFAULT", "from-env")
+        .with_stdout_contains("ENV_TEST_FORCED:from-config")
+        .with_stdout_contains("ENV_TEST_UNFORCED:from-env")
+        .with_stdout_contains("ENV_TEST_UNFORCED_DEFAULT:from-env")
+        .run();
+}
+
+#[cargo_test]
+fn env_relative() {
+    let p = project()
+        .file("Cargo.toml", &basic_bin_manifest("foo2"))
+        .file(
+            "src/main.rs",
+            r#"
+        use std::env;
+        use std::path::Path;
+        fn main() {
+            println!( "ENV_TEST_REGULAR:{}", env!("ENV_TEST_REGULAR") );
+            println!( "ENV_TEST_REGULAR_DEFAULT:{}", env!("ENV_TEST_REGULAR_DEFAULT") );
+            println!( "ENV_TEST_RELATIVE:{}", env!("ENV_TEST_RELATIVE") );
+
+            assert!( Path::new(env!("ENV_TEST_RELATIVE")).is_absolute() );
+            assert!( !Path::new(env!("ENV_TEST_REGULAR")).is_absolute() );
+            assert!( !Path::new(env!("ENV_TEST_REGULAR_DEFAULT")).is_absolute() );
+        }
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+                [env]
+                ENV_TEST_REGULAR = { value = "Cargo.toml", relative = false }
+                ENV_TEST_REGULAR_DEFAULT = "Cargo.toml"
+                ENV_TEST_RELATIVE = { value = "Cargo.toml", relative = true }
+            "#,
+        )
+        .build();
+
+    p.cargo("run -Zconfigurable-env")
+        .masquerade_as_nightly_cargo()
+        .run();
+}

tests/testsuite/main.rs

@@ -24,6 +24,7 @@ mod build_script_extra_link_arg;
 mod cache_messages;
 mod cargo_alias_config;
 mod cargo_command;
+mod cargo_env_config;
 mod cargo_features;
 mod cargo_targets;
 mod cfg;