refactor: centralize environment variable access

- Add util/env_var.rs module with semantic helpers
- Replace direct std::env calls across codebase
- Improve maintainability and testability of env var usage

Author: dk19y

crates/chat-cli/src/api_client/mod.rs

@@ -100,7 +100,7 @@ pub struct ApiClient {
 
 impl ApiClient {
     pub async fn new(
-        env: &Env,
+        _env: &Env,
         fs: &Fs,
         database: &mut Database,
         // endpoint is only passed here for list_profiles where it needs to be called for each region
@@ -138,7 +138,7 @@ impl ApiClient {
                 model_cache: Arc::new(RwLock::new(None)),
             };
 
-            if let Ok(json) = env.get("Q_MOCK_CHAT_RESPONSE") {
+            if let Some(json) = crate::util::env_var::get_mock_chat_response() {
                 this.set_mock_output(serde_json::from_str(fs.read_to_string(json).await.unwrap().as_str()).unwrap());
             }
 
@@ -148,7 +148,7 @@ impl ApiClient {
         // If SIGV4_AUTH_ENABLED is true, use Q developer client
         let mut streaming_client = None;
         let mut sigv4_streaming_client = None;
-        match env.get("AMAZON_Q_SIGV4").is_ok() {
+        match crate::util::env_var::is_sigv4_enabled() {
             true => {
                 let credentials_chain = CredentialsChain::new().await;
                 if let Err(err) = credentials_chain.provide_credentials().await {

crates/chat-cli/src/auth/builder_id.rs

@@ -63,6 +63,7 @@ use crate::database::{
     Database,
     Secret,
 };
+use crate::util::env_var::is_sigv4_enabled;
 
 #[derive(Debug, Copy, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 pub enum OAuthFlow {
@@ -545,7 +546,7 @@ pub async fn poll_create_token(
 
 pub async fn is_logged_in(database: &mut Database) -> bool {
     // Check for BuilderId if not using Sigv4
-    if std::env::var("AMAZON_Q_SIGV4").is_ok_and(|v| !v.is_empty()) {
+    if is_sigv4_enabled() {
         debug!("logged in using sigv4 credentials");
         return true;
     }

crates/chat-cli/src/aws_common/user_agent_override_interceptor.rs

@@ -125,7 +125,7 @@ impl Intercept for UserAgentOverrideInterceptor {
     }
 }
 
-fn apply_additional_metadata(env: &Env, ua: &mut AwsUserAgent) {
+fn apply_additional_metadata(_env: &Env, ua: &mut AwsUserAgent) {
     let ver = format!("{VERSION_HEADER}/{VERSION_VALUE}");
     match AdditionalMetadata::new(clean_metadata(&ver)) {
         Ok(md) => {
@@ -134,7 +134,7 @@ fn apply_additional_metadata(env: &Env, ua: &mut AwsUserAgent) {
         Err(err) => panic!("Failed to parse version: {err}"),
     };
 
-    if let Ok(val) = env.get(AWS_TOOLING_USER_AGENT) {
+    if let Some(val) = crate::util::env_var::get_aws_tooling_user_agent() {
         match AdditionalMetadata::new(clean_metadata(&val)) {
             Ok(md) => {
                 ua.add_additional_metadata(md);

crates/chat-cli/src/cli/chat/cli/editor.rs

@@ -11,6 +11,7 @@ use crate::cli::chat::{
     ChatState,
 };
 use crate::theme::StyledText;
+use crate::util::env_var::get_editor;
 
 #[deny(missing_docs)]
 #[derive(Debug, PartialEq, Args)]
@@ -86,7 +87,7 @@ impl EditorArgs {
 /// Launch the user's preferred editor with the given file path
 fn launch_editor(file_path: &std::path::Path) -> Result<(), ChatError> {
     // Get the editor from environment variable or use a default
-    let editor_cmd = std::env::var("EDITOR").unwrap_or_else(|_| "vi".to_string());
+    let editor_cmd = get_editor();
 
     // Parse the editor command to handle arguments
     let mut parts =

crates/chat-cli/src/cli/chat/tools/delegate.rs

@@ -41,6 +41,7 @@ use crate::cli::{
 };
 use crate::os::Os;
 use crate::theme::StyledText;
+use crate::util::env_var::get_all_env_vars;
 
 /// Launch and manage async agent processes. Delegate tasks to agents that run independently in
 /// background.
@@ -333,7 +334,7 @@ pub async fn spawn_agent_process(os: &Os, agent: &str, task: &str) -> Result<Age
     cmd.stdout(std::process::Stdio::piped());
     cmd.stderr(std::process::Stdio::piped());
     cmd.stdin(std::process::Stdio::null()); // No user input
-    cmd.envs(std::env::vars());
+    cmd.envs(get_all_env_vars());
 
     #[cfg(not(windows))]
     cmd.process_group(0);

crates/chat-cli/src/cli/chat/tools/execute/unix.rs

@@ -16,6 +16,7 @@ use super::{
     format_output,
 };
 use crate::os::Os;
+use crate::util::env_var::get_chat_shell;
 
 /// Run a bash command on Unix systems.
 /// # Arguments
@@ -30,7 +31,7 @@ pub async fn run_command<W: Write>(
     max_result_size: usize,
     mut updates: Option<W>,
 ) -> Result<CommandResult> {
-    let shell = std::env::var("AMAZON_Q_CHAT_SHELL").unwrap_or("bash".to_string());
+    let shell = get_chat_shell();
 
     // Set up environment variables with user agent metadata for CloudTrail tracking
     let env_vars = env_vars_with_user_agent(os);

crates/chat-cli/src/cli/chat/tools/mod.rs

@@ -444,9 +444,9 @@ fn format_path(cwd: impl AsRef<Path>, path: impl AsRef<Path>) -> String {
         .unwrap_or(path.as_ref().to_string_lossy().to_string())
 }
 
-fn supports_truecolor(os: &Os) -> bool {
+fn supports_truecolor(_os: &Os) -> bool {
     // Simple override to disable truecolor since shell_color doesn't use Context.
-    !os.env.get("Q_DISABLE_TRUECOLOR").is_ok_and(|s| !s.is_empty())
+    !crate::util::env_var::is_truecolor_disabled()
         && shell_color::get_color_support().contains(shell_color::ColorSupport::TERM24BIT)
 }
 
@@ -514,7 +514,7 @@ pub fn queue_function_result(result: &str, updates: &mut impl Write, is_error: b
 
 /// Helper function to set up environment variables with user agent metadata for CloudTrail tracking
 pub fn env_vars_with_user_agent(os: &Os) -> std::collections::HashMap<String, String> {
-    let mut env_vars: std::collections::HashMap<String, String> = std::env::vars().collect();
+    let mut env_vars: std::collections::HashMap<String, String> = crate::util::env_var::get_all_env_vars().collect();
 
     // Set up additional metadata for the AWS CLI user agent
     let user_agent_metadata_value = format!(

crates/chat-cli/src/cli/chat/util/mod.rs

@@ -16,6 +16,7 @@ use eyre::Result;
 
 use super::ChatError;
 use super::token_counter::TokenCounter;
+use crate::util::env_var::get_term;
 
 pub fn truncate_safe(s: &str, max_bytes: usize) -> &str {
     if s.len() <= max_bytes {
@@ -119,7 +120,7 @@ pub fn play_notification_bell(requires_confirmation: bool) {
 /// Determine if we should play the bell based on terminal type
 fn should_play_bell() -> bool {
     // Get the TERM environment variable
-    if let Ok(term) = std::env::var("TERM") {
+    if let Some(term) = get_term() {
         // List of terminals known to handle bell character well
         let bell_compatible_terms = [
             "xterm",

crates/chat-cli/src/cli/mod.rs

@@ -1,4 +1,8 @@
 use crate::theme::StyledText;
+use crate::util::env_var::{
+    get_aws_region,
+    is_log_stdout_enabled,
+};
 mod agent;
 pub mod chat;
 mod debug;
@@ -231,7 +235,7 @@ impl Cli {
                 ),
                 false => None,
             },
-            log_to_stdout: std::env::var_os("Q_LOG_STDOUT").is_some() || self.verbose > 0,
+            log_to_stdout: is_log_stdout_enabled() || self.verbose > 0,
             log_file_path: match subcommand {
                 RootSubcommand::Chat { .. } => Some(logs_dir().expect("home dir must be set").join("qchat.log")),
                 _ => None,
@@ -240,7 +244,7 @@ impl Cli {
         });
 
         // Check for region support.
-        if let Ok(region) = std::env::var("AWS_REGION") {
+        if let Ok(region) = get_aws_region() {
             if GOV_REGIONS.contains(&region.as_str()) {
                 bail!("AWS GovCloud ({region}) is not supported.")
             }

crates/chat-cli/src/cli/settings.rs

@@ -10,7 +10,6 @@ use crossterm::style::Stylize;
 use eyre::{
     Result,
     WrapErr,
-    bail,
 };
 use globset::Glob;
 use serde_json::json;
@@ -190,12 +189,11 @@ impl SettingsArgs {
         match self.cmd {
             Some(SettingsSubcommands::Open) => {
                 let file = directories::settings_path().context("Could not get settings path")?;
-                if let Ok(editor) = os.env.get("EDITOR") {
-                    tokio::process::Command::new(editor).arg(file).spawn()?.wait().await?;
-                    Ok(ExitCode::SUCCESS)
-                } else {
-                    bail!("The EDITOR environment variable is not set")
-                }
+
+                let editor =
+                    crate::util::env_var::try_get_editor().context("The EDITOR environment variable is not set")?;
+                tokio::process::Command::new(editor).arg(file).spawn()?.wait().await?;
+                Ok(ExitCode::SUCCESS)
             },
             Some(SettingsSubcommands::List { all, format, state }) => {
                 if state {