feat: allow users to get the principal id of the current identity

e2e/bats/identity.bash

@@ -18,6 +18,27 @@ teardown() {
     rm -rf $(pwd)/home-for-test
 }
 
+
+@test "identity get-principal: the get-principal is the same as sender id" {
+    install_asset identity
+    dfx_start
+    assert_command dfx identity new jose
+
+    PRINCPAL_ID=$(dfx --identity jose identity get-principal)
+
+    dfx --identity jose canister create e2e_project
+    dfx --identity jose build e2e_project
+    dfx --identity jose canister install e2e_project
+
+    assert_command dfx --identity jose canister call e2e_project amInitializer
+
+    SENDER_ID=$(dfx --identity jose canister call e2e_project fromCall)
+
+    if [ "$PRINCPAL_ID" -ne "$SENDER_ID" ]; then
+      echo "IDs did not match: Principal '${PRINCPAL_ID}' != Sender '${SENDER_ID}'..." | fail
+    fi  
+}
+
 @test "calls and query receive the same principal from dfx" {
     install_asset identity
     dfx_start

e2e/bats/identity_command.bash

@@ -12,6 +12,22 @@ teardown() {
     rm -rf $TEMPORARY_HOME
 }
 
+##
+## dfx identity get-principal
+##
+
+@test "identity get-principal: different identities have different principal ids" {
+    assert_command dfx identity new jose
+    assert_command dfx identity new juana
+
+    PRINCPAL_ID_JOSE=$(dfx --identity jose identity get-principal)
+    PRINCPAL_ID_JUANA=$(dfx --identity juana identity get-principal)
+
+    if [ "$PRINCPAL_ID_JOSE" -eq "$PRINCPAL_ID_JUANA" ]; then
+      echo "IDs should not match: Jose '${PRINCPAL_ID_JOSE}' == Juana '${PRINCPAL_ID_JUANA}'..." | fail
+    fi  
+}
+
 ##
 ## dfx identity list
 ##

src/dfx/src/commands/identity/mod.rs

@@ -6,6 +6,7 @@ use clap::{App, ArgMatches, SubCommand};
 
 mod list;
 mod new;
+mod principal;
 mod remove;
 mod rename;
 mod r#use;
@@ -19,6 +20,7 @@ fn builtins() -> Vec<CliCommand> {
         CliCommand::new(rename::construct(), rename::exec),
         CliCommand::new(r#use::construct(), r#use::exec),
         CliCommand::new(whoami::construct(), whoami::exec),
+        CliCommand::new(principal::construct(), principal::exec),
     ]
 }
 

src/dfx/src/commands/identity/principal.rs

@@ -0,0 +1,16 @@
+use crate::lib::environment::Environment;
+use crate::lib::error::DfxResult;
+use crate::lib::identity::identity_manager::IdentityManager;
+use crate::lib::message::UserMessage;
+use clap::{App, ArgMatches, SubCommand};
+
+pub fn construct() -> App<'static, 'static> {
+    SubCommand::with_name("get-principal").about(UserMessage::GetPrincipalId.to_str())
+}
+
+pub fn exec(env: &dyn Environment, _args: &ArgMatches<'_>) -> DfxResult {
+    let identity = IdentityManager::new(env)?.instantiate_selected_identity()?;
+    let principal_id = identity.sender()?;
+    println!("{}", principal_id.to_text());
+    Ok(())
+}

src/dfx/src/lib/message.rs

@@ -126,6 +126,9 @@ user_message!(
     // dfx identity whoami
     ShowIdentity => "Shows the name of the current identity.",
 
+    // dfx identity get-principal
+    GetPrincipalId => "Shows the textual representation of the Principal associated with the current identity.",
+
     // dfx new
     CreateProject => "Creates a new project.",
     ProjectName => "Specifies the name of the project to create.",