refactor: Environment.get_agent() returns an agent or panics (#3408)

The Environment on the call stack is either an AgentEnvironment, or it isn't.  All of these `.ok_or_else`/`.expect` checks either always fail, or never fail.  They never fail.  They're all unreachable.

This PR changes `Environment::get_agent()` to return an `&Agent` rather than an `Option<&Agent>`, and removes all of the unreachable error checking.

src/dfx/src/commands/canister/call.rs

@@ -263,9 +263,7 @@ pub async fn exec(
     // Get the argument, get the type, convert the argument to the type and return
     // an error if any of it doesn't work.
     let arg_value = blob_from_arguments(arguments, opts.random.as_deref(), arg_type, &method_type)?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/canister/delete.rs

@@ -10,7 +10,7 @@ use crate::lib::operations::canister::{
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::util::assets::wallet_wasm;
 use crate::util::blob_from_arguments;
-use anyhow::{anyhow, Context};
+use anyhow::Context;
 use candid::Principal;
 use clap::Parser;
 use dfx_core::canister::build_wallet_canister;
@@ -149,9 +149,7 @@ async fn delete_canister(
                     "Canister {canister} has not been stopped. Delete anyway?"
                 ))?;
             }
-            let agent = env
-                .get_agent()
-                .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+            let agent = env.get_agent();
             let mgr = ManagementCanister::create(agent);
             let canister_id =
                 Principal::from_text(canister).or_else(|_| canister_id_store.get(canister))?;

src/dfx/src/commands/canister/info.rs

@@ -17,9 +17,7 @@ pub struct InfoOpts {
 }
 
 pub async fn exec(env: &dyn Environment, opts: InfoOpts) -> DfxResult {
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let callee_canister = opts.canister.as_str();
     let canister_id_store = env.get_canister_id_store()?;

src/dfx/src/commands/canister/metadata.rs

@@ -1,7 +1,7 @@
 use crate::lib::error::DfxResult;
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::Environment;
-use anyhow::{anyhow, Context};
+use anyhow::Context;
 use candid::Principal;
 use clap::Parser;
 use std::io::{stdout, Write};
@@ -17,9 +17,7 @@ pub struct CanisterMetadataOpts {
 }
 
 pub async fn exec(env: &dyn Environment, opts: CanisterMetadataOpts) -> DfxResult {
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let callee_canister = opts.canister_name.as_str();
     let canister_id_store = env.get_canister_id_store()?;

src/dfx/src/commands/canister/request_status.rs

@@ -3,7 +3,7 @@ use crate::lib::error::{DfxError, DfxResult};
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::util::clap::parsers;
 use crate::util::print_idl_blob;
-use anyhow::{anyhow, Context};
+use anyhow::Context;
 use backoff::backoff::Backoff;
 use backoff::ExponentialBackoff;
 use candid::Principal;
@@ -36,9 +36,7 @@ pub struct RequestStatusOpts {
 pub async fn exec(env: &dyn Environment, opts: RequestStatusOpts) -> DfxResult {
     let request_id =
         RequestId::from_str(&opts.request_id[2..]).context("Invalid argument: request_id")?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/canister/sign.rs

@@ -125,9 +125,7 @@ pub async fn exec(
     // Get the argument, get the type, convert the argument to the type and return
     // an error if any of it doesn't work.
     let arg_value = blob_from_arguments(arguments, opts.random.as_deref(), arg_type, &method_type)?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let network = env
         .get_network_descriptor()

src/dfx/src/commands/deps/deploy.rs

@@ -7,7 +7,7 @@ use crate::lib::deps::{
 use crate::lib::environment::Environment;
 use crate::lib::error::DfxResult;
 use crate::lib::root_key::fetch_root_key_if_needed;
-use anyhow::anyhow;
+
 use candid::Principal;
 use clap::Parser;
 use fn_error_context::context;
@@ -38,9 +38,7 @@ pub async fn exec(env: &dyn Environment, opts: DepsDeployOpts) -> DfxResult {
     let init_json = load_init_json(&project_root)?;
 
     fetch_root_key_if_needed(env).await?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let canister_ids = match &opts.canister {
         Some(canister) => {

src/dfx/src/commands/deps/pull.rs

@@ -53,9 +53,7 @@ pub async fn exec(env: &dyn Environment, opts: DepsPullOpts) -> DfxResult {
 
     fetch_root_key_if_needed(&env).await?;
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let all_dependencies =
         resolve_all_dependencies(agent, logger, &pull_canisters_in_config).await?;

src/dfx/src/commands/identity/set_wallet.rs

@@ -57,9 +57,7 @@ pub fn exec(env: &dyn Environment, opts: SetWalletOpts, network: NetworkOpt) ->
             "Skipping verification of availability of the canister on the network due to --force..."
         );
     } else {
-        let agent = env
-            .get_agent()
-            .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+        let agent = env.get_agent();
 
         runtime
             .block_on(async {

src/dfx/src/commands/ledger/balance.rs

@@ -34,9 +34,7 @@ pub async fn exec(env: &dyn Environment, opts: BalanceOpts) -> DfxResult {
             |v| AccountIdentifier::from_str(&v),
         )
         .map_err(|err| anyhow!(err))?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     let balance = ledger::balance(agent, &acc_id, opts.ledger_canister_id).await?;
 

src/dfx/src/commands/ledger/create_canister.rs

@@ -9,7 +9,7 @@ use crate::lib::nns_types::icpts::{ICPTs, TRANSACTION_FEE};
 use crate::lib::operations::cmc::{notify_create, transfer_cmc};
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::util::clap::parsers::e8s_parser;
-use anyhow::{anyhow, bail, Context};
+use anyhow::{bail, Context};
 use candid::Principal;
 use clap::Parser;
 
@@ -71,9 +71,7 @@ pub async fn exec(env: &dyn Environment, opts: CreateCanisterOpts) -> DfxResult
         )
     })?;
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/ledger/notify/create_canister.rs

@@ -3,7 +3,7 @@ use crate::lib::ledger_types::NotifyError::Refunded;
 use crate::lib::operations::cmc::notify_create;
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::lib::{environment::Environment, error::DfxResult};
-use anyhow::{anyhow, bail};
+use anyhow::bail;
 use candid::Principal;
 use clap::Parser;
 
@@ -27,9 +27,7 @@ pub async fn exec(env: &dyn Environment, opts: NotifyCreateOpts) -> DfxResult {
     let block_height = opts.block_height;
     let controller = opts.controller;
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/ledger/notify/top_up.rs

@@ -3,7 +3,7 @@ use crate::lib::ledger_types::NotifyError::Refunded;
 use crate::lib::operations::cmc::notify_top_up;
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::lib::{environment::Environment, error::DfxResult};
-use anyhow::{anyhow, bail};
+use anyhow::bail;
 use candid::Principal;
 use clap::Parser;
 
@@ -21,9 +21,7 @@ pub async fn exec(env: &dyn Environment, opts: NotifyTopUpOpts) -> DfxResult {
     let block_height = opts.block_height;
     let canister = opts.canister;
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/ledger/show_subnet_types.rs

@@ -2,7 +2,7 @@ use crate::lib::environment::Environment;
 use crate::lib::error::DfxResult;
 use crate::lib::ledger_types::{GetSubnetTypesToSubnetsResult, MAINNET_CYCLE_MINTER_CANISTER_ID};
 use crate::lib::root_key::fetch_root_key_if_needed;
-use anyhow::{anyhow, Context};
+use anyhow::Context;
 use candid::{Decode, Encode, Principal};
 use clap::Parser;
 
@@ -17,9 +17,7 @@ pub struct ShowSubnetTypesOpts {
 }
 
 pub async fn exec(env: &dyn Environment, opts: ShowSubnetTypesOpts) -> DfxResult {
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/ledger/top_up.rs

@@ -8,7 +8,7 @@ use crate::lib::nns_types::icpts::{ICPTs, TRANSACTION_FEE};
 use crate::lib::operations::cmc::{notify_top_up, transfer_cmc};
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::util::clap::parsers::e8s_parser;
-use anyhow::{anyhow, bail, Context};
+use anyhow::{bail, Context};
 use candid::Principal;
 use clap::Parser;
 
@@ -65,9 +65,7 @@ pub async fn exec(env: &dyn Environment, opts: TopUpOpts) -> DfxResult {
         )
     })?;
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/ledger/transfer.rs

@@ -70,9 +70,7 @@ pub async fn exec(env: &dyn Environment, opts: TransferOpts) -> DfxResult {
         })?
         .to_address();
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
 

src/dfx/src/commands/quickstart.rs

@@ -45,7 +45,7 @@ pub struct QuickstartOpts;
 
 pub fn exec(env: &dyn Environment, _: QuickstartOpts) -> DfxResult {
     let env = create_agent_environment(env, Some("ic".to_string()))?;
-    let agent = env.get_agent().expect("Unable to create agent");
+    let agent = env.get_agent();
     let ident = env.get_selected_identity().unwrap();
     let principal = env.get_selected_identity_principal().unwrap();
     eprintln!("Your DFX user principal: {principal}");

src/dfx/src/commands/wallet/redeem_faucet_coupon.rs

@@ -33,9 +33,7 @@ pub async fn exec(env: &dyn Environment, opts: RedeemFaucetCouponOpts) -> DfxRes
     } else {
         Principal::from_text(DEFAULT_FAUCET_PRINCIPAL).unwrap()
     };
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
     if fetch_root_key_if_needed(env).await.is_err() {
         bail!("Failed to connect to the local replica. Did you forget to use '--network ic'?");
     } else if !env.get_network_descriptor().is_ic {

src/dfx/src/commands/wallet/upgrade.rs

@@ -4,7 +4,7 @@ use crate::lib::identity::wallet::wallet_canister_id;
 use crate::lib::operations::canister::install_canister::install_wallet;
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::lib::state_tree::canister_info::read_state_tree_canister_module_hash;
-use anyhow::{anyhow, bail};
+use anyhow::bail;
 use clap::Parser;
 use ic_utils::interfaces::management_canister::builders::InstallMode;
 
@@ -31,9 +31,7 @@ pub async fn exec(env: &dyn Environment, _opts: UpgradeOpts) -> DfxResult {
         );
     };
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     fetch_root_key_if_needed(env).await?;
     if read_state_tree_canister_module_hash(agent, canister_id)
@@ -43,9 +41,7 @@ pub async fn exec(env: &dyn Environment, _opts: UpgradeOpts) -> DfxResult {
         bail!("The cycles wallet canister is empty. Try running `dfx identity deploy-wallet` to install code for the cycles wallet in this canister.")
     }
 
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
 
     install_wallet(env, agent, canister_id, InstallMode::Upgrade).await?;
 

src/dfx/src/lib/environment.rs

@@ -43,7 +43,7 @@ pub trait Environment {
 
     // Explicit lifetimes are actually needed for mockall to work properly.
     #[allow(clippy::needless_lifetimes)]
-    fn get_agent<'a>(&'a self) -> Option<&'a Agent>;
+    fn get_agent<'a>(&'a self) -> &'a Agent;
 
     #[allow(clippy::needless_lifetimes)]
     fn get_network_descriptor<'a>(&'a self) -> &'a NetworkDescriptor;
@@ -210,10 +210,8 @@ impl Environment for EnvironmentImpl {
         &self.identity_override
     }
 
-    fn get_agent(&self) -> Option<&Agent> {
-        // create an AgentEnvironment explicitly, in order to specify network and agent.
-        // See install, build for examples.
-        None
+    fn get_agent(&self) -> &Agent {
+        unreachable!("Agent only available from an AgentEnvironment");
     }
 
     fn get_network_descriptor(&self) -> &NetworkDescriptor {
@@ -337,8 +335,8 @@ impl<'a> Environment for AgentEnvironment<'a> {
         self.backend.get_identity_override()
     }
 
-    fn get_agent(&self) -> Option<&Agent> {
-        Some(&self.agent)
+    fn get_agent(&self) -> &Agent {
+        &self.agent
     }
 
     fn get_network_descriptor(&self) -> &NetworkDescriptor {

src/dfx/src/lib/identity/wallet.rs

@@ -3,7 +3,7 @@ use crate::lib::error::DfxResult;
 use crate::lib::root_key::fetch_root_key_if_needed;
 use crate::util::assets::wallet_wasm;
 use crate::Environment;
-use anyhow::{anyhow, bail, Context};
+use anyhow::{bail, Context};
 use candid::Principal;
 use dfx_core::canister::build_wallet_canister;
 use dfx_core::config::directories::get_user_dfx_config_dir;
@@ -83,9 +83,7 @@ pub async fn create_wallet(
     some_canister_id: Option<Principal>,
 ) -> DfxResult<Principal> {
     fetch_root_key_if_needed(env).await?;
-    let agent = env
-        .get_agent()
-        .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+    let agent = env.get_agent();
     let mgr = ManagementCanister::create(agent);
     info!(
         env.get_logger(),
@@ -161,9 +159,7 @@ pub async fn get_or_create_wallet_canister<'env>(
     // without this async block, #[context] gives a spurious error
     async {
         let wallet_canister_id = get_or_create_wallet(env, network, name).await?;
-        let agent = env
-            .get_agent()
-            .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?;
+        let agent = env.get_agent();
         build_wallet_canister(wallet_canister_id, agent)
             .await
             .map_err(Into::into)

src/dfx/src/lib/migrate.rs

@@ -19,9 +19,7 @@ pub async fn migrate(env: &dyn Environment, network: &NetworkDescriptor, fix: bo
     fetch_root_key_if_needed(env).await?;
     let config = env.get_config_or_anyhow()?;
     let config = config.get_config();
-    let agent = env
-        .get_agent()
-        .expect("Could not get agent from environment");
+    let agent = env.get_agent();
     let mut mgr = env.new_identity_manager()?;
     let ident = mgr.instantiate_selected_identity(env.get_logger())?;
     let mut did_migrate = false;

src/dfx/src/lib/named_canister.rs

@@ -30,10 +30,7 @@ pub async fn install_ui_canister(
         ));
     }
     fetch_root_key_if_needed(env).await?;
-    let mgr = ManagementCanister::create(
-        env.get_agent()
-            .ok_or_else(|| anyhow!("Cannot get HTTP client from environment."))?,
-    );
+    let mgr = ManagementCanister::create(env.get_agent());
     info!(
         env.get_logger(),
         "Creating UI canister on the {} network.", network.name