Fix the debug config feature and --debug flag.

lib/cli/Cargo.toml

@@ -45,7 +45,9 @@ distance = "0.4"
 # For the inspect subcommand
 bytesize = "1.0"
 cfg-if = "0.1"
-
+# For debug feature
+fern = { version = "0.6", features = ["colored"], optional = true }
+log = { version = "0.4", optional = true }
 
 [features]
 # Don't add the compiler features in default, please add them on the Makefile
@@ -94,3 +96,4 @@ llvm = [
     "wasmer-compiler-llvm",
     "compiler",
 ]
+debug = ["fern", "log"]

lib/cli/src/commands/run.rs

@@ -1,4 +1,5 @@
 use crate::common::get_cache_dir;
+use crate::logging;
 use crate::store::{CompilerType, EngineType, StoreOptions};
 use crate::suggestions::suggest_function_exports;
 use crate::warning;
@@ -70,6 +71,10 @@ pub struct Run {
 impl Run {
     /// Execute the run command
     pub fn execute(&self) -> Result<()> {
+        #[cfg(feature = "debug")]
+        if self.debug {
+            logging::set_up_logging().unwrap();
+        }
         self.inner_execute().with_context(|| {
             let compilers = CompilerType::enabled()
                 .iter()

lib/cli/src/logging.rs

@@ -1,3 +1,4 @@
+//! Logging functions for the debug feature.
 use crate::utils::wasmer_should_print_color;
 use fern::colors::{Color, ColoredLevelConfig};
 use std::time;

lib/wasi/Cargo.toml

@@ -16,7 +16,7 @@ byteorder = "1.3"
 thiserror = "1"
 generational-arena = { version = "0.2", features = ["serde"] }
 libc = { version = "^0.2.69", default-features = false }
-tracing = "0.1"
+tracing = { version = "0.1", features = ["log"] }
 getrandom = "0.1"
 time = "0.1"
 typetag = "0.1"