build: only set polars version metadata when building with polars f…

…eature

build.rs

@@ -1,8 +1,3 @@
-use std::{fs, path::Path};
-
-// This is the string that is searched for in Cargo.toml to find the Polars revision
-const QSV_POLARS_REV: &str = "# QSV_POLARS_REV=";
-
 fn main() {
     // we use TARGET in --version and user-agent strings
     println!(
@@ -16,24 +11,33 @@ fn main() {
         std::env::var("QSV_KIND").unwrap_or_else(|_| "compiled".to_string())
     );
 
-    // QSV_POLARS_REV contains either the commit id short hash or the git tag
-    // of the Polars version qsv was built against
-    let cargo_toml_path = Path::new("Cargo.toml");
-    let cargo_toml_content =
-        fs::read_to_string(cargo_toml_path).expect("Failed to read Cargo.toml");
-    let polars_rev = cargo_toml_content
-        .find(QSV_POLARS_REV)
-        .map_or_else(String::new, |index| {
-            let start_index = index + QSV_POLARS_REV.len();
-            let end_index = cargo_toml_content[start_index..]
-                .find('\n')
-                .map_or(cargo_toml_content.len(), |i| start_index + i);
-            cargo_toml_content[start_index..end_index]
-                .trim()
-                .to_string()
-        });
-    println!(
-        "cargo:rustc-env=QSV_POLARS_REV={}",
-        std::env::var("QSV_POLARS_REV").unwrap_or(polars_rev)
-    );
+    #[cfg(feature = "polars")]
+    {
+        use std::{fs, path::Path};
+
+        // This is the string that is searched for in Cargo.toml to find the Polars revision
+        const QSV_POLARS_REV: &str = "# QSV_POLARS_REV=";
+
+        // QSV_POLARS_REV contains either the commit id short hash or the git tag
+        // of the Polars version qsv was built against
+        let cargo_toml_path = Path::new("Cargo.toml");
+        let cargo_toml_content =
+            fs::read_to_string(cargo_toml_path).expect("Failed to read Cargo.toml");
+        let polars_rev =
+            cargo_toml_content
+                .find(QSV_POLARS_REV)
+                .map_or_else(String::new, |index| {
+                    let start_index = index + QSV_POLARS_REV.len();
+                    let end_index = cargo_toml_content[start_index..]
+                        .find('\n')
+                        .map_or(cargo_toml_content.len(), |i| start_index + i);
+                    cargo_toml_content[start_index..end_index]
+                        .trim()
+                        .to_string()
+                });
+        println!(
+            "cargo:rustc-env=QSV_POLARS_REV={}",
+            std::env::var("QSV_POLARS_REV").unwrap_or(polars_rev)
+        );
+    }
 }