fix(tools): allow using env vars in tools

docs/dev-tools/index.md

@@ -22,6 +22,9 @@ It's also compatible
 with asdf `.tool-versions` files as well as [idiomatic version files](/configuration#idiomatic-version-files) like `.node-version` and
 `.ruby-version`. See [configuration](/configuration) for more details.
 
+When specifying tool versions, you can also refer to environment variables defined in the same file, but note
+that environment variables from referenced files are not resolved here.
+
 ::: info
 mise is inspired by [asdf](https://asdf-vm.com) and can leverage asdf's
 vast [plugin ecosystem](https://github.com/mise-plugins/registry)

docs/templates.md

@@ -20,8 +20,12 @@ Here is an example of a `mise.toml` file that uses templates:
 ```toml
 [env]
 PROJECT_NAME = "{{ cwd | basename }}"
+TERRAFORM_VERSION = "1.0.0"
 
 [tools]
+# refers to env variable defined in this file
+terraform = "{{ env.TERRAFORM_VERSION }}"
+# refers to external env variable
 node = "{{ get_env(name='NODE_VERSION', default='20') }}"
 ```
 

src/config/config_file/mise_toml.rs

@@ -22,7 +22,7 @@ use crate::config::config_file::{config_root, toml::deserialize_arr};
 use crate::config::env_directive::{AgeFormat, EnvDirective, EnvDirectiveOptions, RequiredValue};
 use crate::config::settings::SettingsPartial;
 use crate::config::{Alias, AliasMap, Config};
-use crate::file;
+use crate::env_diff::EnvMap;
 use crate::file::{create_dir_all, display_path};
 use crate::hooks::{Hook, Hooks};
 use crate::redactions::Redactions;
@@ -31,6 +31,7 @@ use crate::task::Task;
 use crate::tera::{BASE_CONTEXT, get_tera};
 use crate::toolset::{ToolRequest, ToolRequestSet, ToolSource, ToolVersionOptions};
 use crate::watch_files::WatchFile;
+use crate::{env, file};
 
 use super::{ConfigFileType, min_version::MinVersionSpec};
 
@@ -137,11 +138,13 @@ impl MiseToml {
             "config_root",
             config_root::config_root(path).to_str().unwrap(),
         );
-        Self {
+        let mut rf = Self {
             path: path.to_path_buf(),
             context,
             ..Default::default()
-        }
+        };
+        rf.update_context_env(env::PRISTINE_ENV.clone());
+        rf
     }
 
     pub fn from_file(path: &Path) -> eyre::Result<Self> {
@@ -166,6 +169,7 @@ impl MiseToml {
         rf.context = BASE_CONTEXT.clone();
         rf.context
             .insert("config_root", path.parent().unwrap().to_str().unwrap());
+        rf.update_context_env(env::PRISTINE_ENV.clone());
         rf.path = path.to_path_buf();
         let project_root = rf.project_root().map(|p| p.to_path_buf());
         for task in rf.tasks.0.values_mut() {
@@ -356,6 +360,23 @@ impl MiseToml {
         Ok(())
     }
 
+    // Merge base OS env vars with env sections from this file,
+    // so they are available for templating.
+    // Note this only merges regular key-value variables; referenced files are not resolved.
+    fn update_context_env(&mut self, mut base_env: EnvMap) {
+        let env_vars = self
+            .env
+            .0
+            .iter()
+            .filter_map(|e| match e {
+                EnvDirective::Val(key, value, _) => Some((key.clone(), value.clone())),
+                _ => None,
+            })
+            .collect::<IndexMap<_, _>>();
+        base_env.extend(env_vars);
+        self.context.insert("env", &base_env);
+    }
+
     fn parse_template(&self, input: &str) -> eyre::Result<String> {
         self.parse_template_with_context(&self.context, input)
     }
@@ -1731,6 +1752,30 @@ mod tests {
         });
     }
 
+    #[tokio::test]
+    async fn test_env_var_in_tool() {
+        let _config = Config::get().await.unwrap();
+        let p = CWD.as_ref().unwrap().join(".test.mise.toml");
+        file::write(
+            &p,
+            r#"
+        [env]
+        TERRAFORM_VERSION = '1.0.0'
+        JQ_PREFIX = '1.6'
+
+        [tools]
+        terraform = "{{env.TERRAFORM_VERSION}}"
+        jq = { prefix = "{{ env.JQ_PREFIX }}" }
+        "#,
+        )
+        .unwrap();
+        let cf = MiseToml::from_file(&p).unwrap();
+        assert_snapshot!(replace_path(&format!(
+            "{:#?}",
+            cf.to_tool_request_set().unwrap().tools
+        )));
+    }
+
     #[tokio::test]
     async fn test_env_array_valid() {
         let _config = Config::get().await.unwrap();

src/config/config_file/snapshots/mise__config__config_file__mise_toml__tests__env_var_in_tool.snap

@@ -0,0 +1,34 @@
+---
+source: src/config/config_file/mise_toml.rs
+expression: "replace_path(&format!(\"{:#?}\", cf.to_tool_request_set().unwrap().tools))"
+---
+{
+    BackendArg(terraform): [
+        Version {
+            backend: BackendArg(terraform),
+            version: "1.0.0",
+            options: ToolVersionOptions {
+                os: None,
+                install_env: {},
+                opts: {},
+            },
+            source: MiseToml(
+                "~/cwd/.test.mise.toml",
+            ),
+        },
+    ],
+    BackendArg(jq): [
+        Prefix {
+            backend: BackendArg(jq),
+            prefix: "1.6",
+            options: ToolVersionOptions {
+                os: None,
+                install_env: {},
+                opts: {},
+            },
+            source: MiseToml(
+                "~/cwd/.test.mise.toml",
+            ),
+        },
+    ],
+}