fix(macros): don't mutate environment variables

Author: joeydewaal

sqlx-macros-core/src/query/mod.rs

@@ -111,37 +111,14 @@ static METADATA: Lazy<Mutex<HashMap<String, Metadata>>> = Lazy::new(Default::def
 
 // If we are in a workspace, lookup `workspace_root` since `CARGO_MANIFEST_DIR` won't
 // reflect the workspace dir: https://github.com/rust-lang/cargo/issues/3946
-fn init_metadata(manifest_dir: &String) -> Metadata {
-    let manifest_dir: PathBuf = manifest_dir.into();
+fn init_metadata(manifest_dir_str: &String) -> Metadata {
+    let manifest_dir: PathBuf = manifest_dir_str.into();
 
-    // If a .env file exists at CARGO_MANIFEST_DIR, load environment variables from this,
-    // otherwise fallback to default dotenv behaviour.
-    let env_path = manifest_dir.join(".env");
-
-    #[cfg_attr(not(procmacro2_semver_exempt), allow(unused_variables))]
-    let env_path = if env_path.exists() {
-        // Load the new environment variables and override the old ones if necessary.
-        let res = dotenvy::from_path_override(&env_path);
-        if let Err(e) = res {
-            panic!("failed to load environment from {env_path:?}, {e}");
-        }
-
-        Some(env_path)
-    } else {
-        dotenvy::dotenv_override().ok()
-    };
-
-    // tell the compiler to watch the `.env` for changes, if applicable
-    #[cfg(procmacro2_semver_exempt)]
-    if let Some(env_path) = env_path.as_ref().and_then(|path| path.to_str()) {
-        proc_macro::tracked_path::path(env_path);
-    }
-
-    let offline = env("SQLX_OFFLINE")
+    let offline = env_with_fallback("SQLX_OFFLINE", Some(&manifest_dir_str))
         .map(|s| s.eq_ignore_ascii_case("true") || s == "1")
         .unwrap_or(false);
 
-    let database_url = env("DATABASE_URL").ok();
+    let database_url = env_with_fallback("DATABASE_URL", Some(&manifest_dir_str));
 
     Metadata {
         manifest_dir,
@@ -182,7 +159,7 @@ pub fn expand_input<'a>(
 
             // Check SQLX_OFFLINE_DIR, then local .sqlx, then workspace .sqlx.
             let dirs = [
-                |_: &Metadata| env("SQLX_OFFLINE_DIR").ok().map(PathBuf::from),
+                |_: &Metadata| env_with_fallback("SQLX_OFFLINE_DIR", None).map(PathBuf::from),
                 |meta: &Metadata| Some(meta.manifest_dir.join(".sqlx")),
                 |meta: &Metadata| Some(meta.workspace_root().join(".sqlx")),
             ];
@@ -360,7 +337,7 @@ where
     if !offline {
         // Only save query metadata if SQLX_OFFLINE_DIR is set manually or by `cargo sqlx prepare`.
         // Note: in a cargo workspace this path is relative to the root.
-        if let Ok(dir) = env("SQLX_OFFLINE_DIR") {
+        if let Some(dir) = env_with_fallback("SQLX_OFFLINE_DIR", None) {
             let path = PathBuf::from(&dir);
 
             match fs::metadata(&path) {
@@ -402,3 +379,46 @@ fn env(name: &str) -> Result<String, std::env::VarError> {
         std::env::var(name)
     }
 }
+
+/// Get the value of an environment variable, try .env file if the variable can't be found.
+fn env_with_fallback(name: &str, manifest_dir: Option<&str>) -> Option<String> {
+    let manifest_dir: PathBuf = manifest_dir.map(Into::into).unwrap_or_else(|| {
+        env("CARGO_MANIFEST_DIR")
+            .expect("`CARGO_MANIFEST_DIR` must be set")
+            .into()
+    });
+
+    if let Ok(opt_env) = env(name) {
+        return Some(opt_env);
+    }
+
+    // If a .env file exists at CARGO_MANIFEST_DIR, read environment variables from this,
+    // otherwise fallback to default dotenv file.
+    let env_path = manifest_dir.join(".env");
+
+    #[cfg_attr(not(procmacro2_semver_exempt), allow(unused_variables))]
+    let env_file = if env_path.exists() {
+        match dotenvy::from_path_iter(&env_path) {
+            Ok(iter) => iter,
+            Err(e) => panic!("failed to load environment from {env_path:?}, {e}"),
+        }
+    } else {
+        dotenvy::dotenv_iter().ok()?
+    };
+
+    // tell the compiler to watch the `.env` for changes, if applicable
+    #[cfg(procmacro2_semver_exempt)]
+    if let Some(env_path) = env_path.as_ref().and_then(|path| path.to_str()) {
+        proc_macro::tracked_path::path(env_path);
+    }
+
+    for item in env_file {
+        let Ok((key, value)) = item else {
+            continue;
+        };
+        if key == name {
+            return Some(value);
+        }
+    }
+    None
+}