feat: make measure mode always default to instrumentation

Author: GuillaumeLagrange

crates/cargo-codspeed/src/app.rs

@@ -14,8 +14,6 @@ struct Cli {
 
     /// The measurement tool to use for measuring performance.
     /// Automatically set to `walltime` on macro runners
-    // This is an Option even if MeasurementMode has a default because
-    // the default is dynamic and this would mislead the user
     #[arg(short, long, global = true, env = "CODSPEED_RUNNER_MODE")]
     measurement_mode: Option<MeasurementMode>,
 

crates/cargo-codspeed/src/measurement_mode.rs

@@ -1,22 +1,13 @@
 use clap::ValueEnum;
 use serde::Serialize;
-use std::{env, path::Path};
+use std::path::Path;
 
-#[derive(Debug, Clone, ValueEnum, Serialize, PartialEq, Eq)]
+#[derive(Debug, Clone, ValueEnum, Serialize, PartialEq, Eq, Default)]
 #[serde(rename_all = "lowercase")]
 pub enum MeasurementMode {
-    Walltime,
+    #[default]
     Instrumentation,
-}
-
-impl Default for MeasurementMode {
-    fn default() -> Self {
-        if env::var("CODSPEED_ENV").is_ok() {
-            MeasurementMode::Instrumentation
-        } else {
-            MeasurementMode::Walltime
-        }
-    }
+    Walltime,
 }
 
 impl AsRef<Path> for MeasurementMode {