Updated the way built-in commands are called/used

Previously, built-in commands were fairly primitive, merely outputting
STDOUT and STDERR with the print! macros. However, we need them to
behave like normal programs, that is:

  - Acknowledge their verse's meter (forking, piping, etc.),
  - Ability to capture STDOUT and STDERR (>, 2>),
  - and Affect the currently running environment.

For these reasons, the anthology was reworked, and now contains the
Anthology struct, which mimics both std::process::{Child, Command}.

The AnthologyStdin helper struct was also created, for built-ins to
take input on STDIN, though no built-in is currently using it.

Each built-ins' incant functions were updated to return a
std::process::Output. It contains output from STDOUT, output from
STDERR, and the exit code of the "process".

A fix was also implemented for aliases, where the STDOUT and STDERR
vectors were not being copied to the newly constructed verse.

1 files changed, 42 insertions, 11 deletions

diff --git a/src/poem/anthology/cd.rs b/src/poem/anthology/cd.rs
index 5b39359..bdf04f6 100644
--- a/src/poem/anthology/cd.rs
+++ b/src/poem/anthology/cd.rs
@@ -1,5 +1,6 @@
-use crate::poem::Verse;
 use std::env;
+use std::os::unix::process::ExitStatusExt;
+use std::process::{ExitStatus, Output};
 
 /// cd
 ///
@@ -12,27 +13,57 @@ use std::env;
 /// ```sh
 /// cd ~/.config # Change into /home/<user>/.config
 /// ```
-pub fn incant(verse: &Verse) -> i32 {
-    let path = match verse.clause() {
+pub fn incant(clause: &Option<Vec<String>>, uerr: bool) -> Output {
+    let status;
+    let out: Vec<u8> = Vec::new();
+    let mut err: Vec<u8> = Vec::new();
+    let path = match clause {
         Some(path) => path[0].to_string(),
         None => match env::var("HOME") {
             Ok(val) => val,
             Err(_) => {
-                eprintln!("cd: unknown home, staying in pwd");
-                return 1;
+                status = 1;
+                if uerr {
+                    err.append(&mut "cd: unknown home, staying in pwd\n".as_bytes().to_vec());
+                } else {
+                    eprintln!("cd: unknown home, staying in pwd");
+                }
+                return Output {
+                    status: ExitStatus::from_raw(status),
+                    stdout: out,
+                    stderr: err,
+                };
             }
         },
     };
 
-    match std::env::set_current_dir(&path) {
+    status = match std::env::set_current_dir(&path) {
         Ok(_) => 0,
         Err(e) => {
-            eprintln!(
-                "cd: unable to change into {}: {}",
-                path,
-                e.to_string().to_lowercase()
-            );
+            if uerr {
+                err.append(
+                    &mut format!(
+                        "cd: unable to change into {}: {}\n",
+                        path,
+                        e.to_string().to_lowercase()
+                    )
+                    .as_bytes()
+                    .to_vec(),
+                );
+            } else {
+                eprintln!(
+                    "cd: unable to change into {}: {}",
+                    path,
+                    e.to_string().to_lowercase()
+                );
+            }
             1
         }
+    };
+
+    Output {
+        status: ExitStatus::from_raw(status),
+        stdout: out,
+        stderr: err,
     }
 }