configurable cd hook

Signed-off-by: Ava Affine <ava@sunnypup.io>

Readme.org

@@ -68,6 +68,7 @@ Errors during configuration are non-terminal. In such a case any defaults which
 - CFG_FLESH_L_PROMPT (default 'λ'): a function that is called with no arguments to output the left hand of the prompt
 - CFG_FLESH_R_PROMPT (default ''): a function that is called with no arguments to output the right hand of the prompt
 - CFG_FLESH_PROMPT_DELIMITER (default '>'): a function that is called with no arguments to output the delimiter separating prompt from user input
+- CFG_FLESH_CD_CB (default None): optional function / lambda that is called with no arguments on every change of CD. See [[file:Shell.org][The Shell Documentation]] for more information.
 
 ** Prompt design
 For an example of prompt design see [[file:snippets/mood-prompt.f][the mood prompt]]
@@ -164,18 +165,17 @@ Note: this section only tracks the state of incomplete TODO items. Having everyt
 ** TODO v1.0 tasks
 - Can pass args to flesh scripts (via command line)
 - Can pass args to flesh scripts (via interpreter)
-- Pipe also operates on stderr
-- ~ if possible (string replacement?)
 - tab completion for symbols also attempts to complete binaries
-- finish basic goals in the [[file:snippets/interactive-devel.f][interactive development library]]
+- cd accepts symbols as well as strings (emulate shell)
+- declare macros
 - Release CI
 - Make an icon if you feel like it
 - Post release to relevant channels
 ** TODO v1.1 tasks
-- emacs lsp implementation
-- finish stretch goals in the [[file:snippets/interactive-devel.f][interactive development library]]
+- Pipe also operates on stderr
+- better emacs language mode
+- finish the [[file:snippets/interactive-devel.f][interactive development library]]
 - History length configurable (env var?)
-- execute configurable function on cd
 - Post to relevant channels
 - Implement Compose for lambdas
   (add to readme)

Shell.org

@@ -143,6 +143,9 @@ Flesh also provides a ~cd~ utility to change current working directory:
 (cd (concat HOME '/repositories')) ;; $ cd ~/repositories
 #+END_EXAMPLE
 
+This ~cd~ routine will keep the ~PWD~ variable up to date.
+Every invokation of ~cd~ will call whatever lambda or function is stored in ~CFG_FLESH_CD_CB~ with no arguments. A function stored in this variable can then perform on the fly reconfiguration or set additional variables based on the directory that the user has entered.
+
 ** Creating bindings for shell commands
 Daily Flesh users will long for first class shell commands that are accounted for in autocomplete.
 

src/lib.rs

@@ -33,7 +33,6 @@ pub mod ast {
 }
 
 pub mod stdlib {
-    pub use crate::stl::{};
     pub use crate::stl::{
         dynamic_stdlib, static_stdlib,
         load_defaults, load_environment,

src/stl/posix.rs

@@ -63,6 +63,7 @@ use {
 };
 
 pub const POSIX_LOAD_NAME: &str = "load";
+pub const CD_USER_CB: &str = "CFG_FLESH_CD_CB";
 
 pub struct ShellState {
     pub parent_pid: Pid,
@@ -714,38 +715,69 @@ fn fg_callback(
 }
 
 const CD_DOCSTRING: &str =
-    "Expects 1 argument (a string). Changes to a new directory";
+    "Expects 1 argument (a string). Changes to a new directory.
+If CFG_RELISH_CD_CB is defined, cd will evaluate it.
+cd returns the result that CFG_RELISH_CD_CB returns.";
 fn cd_callback(ast: &Seg, syms: &mut SymTable) -> Result<Ctr, Traceback> {
-    if let Ctr::String(ref dir) = *ast.car {
-        let dirp = Path::new(dir);
-        if let Err(s) = set_current_dir(dirp) {
-            Err(start_trace(
-                ("cd", s.to_string())
-                    .into()))
-        } else {
-            if let Ok(abs) = canonicalize(dirp) {
+    let dir: &String;
+    match *ast.car {
+        Ctr::String(ref d) => dir = d,
+        Ctr::Symbol(ref d) => dir = d,
+        Ctr::Seg(ref s) => {
+            match eval(s, syms) {
+                Ok(r) => {
+                    if r == ast.car {
+                        return Err(start_trace(("cd", "innapropriate input.").into()));
+                    }
+                    return cd_callback(&Seg::from_mono(r), syms);
+                }
+                Err(e) => {
+                    return Err(e.with_trace(("cd", "couldnt evaluate input").into()));
+                }
+            }
+        },
+        _ => return Err(start_trace(
+            ("cd", "expected input to be a string or symbol")
+                .into()))
+    }
+
+    let dirp = Path::new(dir);
+    match canonicalize(dirp) {
+        Ok(abs) => {
+            if let Err(s) = set_current_dir(dirp) {
+                Err(start_trace(
+                    ("cd", s.to_string())
+                        .into()))
+            } else {
                 syms.insert(
                     String::from("PWD"),
                     Symbol::from_ast(
                         &String::from("PWD"),
-                        &String::from("current working directory"),
+                        &String::from("current working directory, set by cd"),
                         &Seg::from_mono(Box::new(
                             Ctr::String(abs.to_string_lossy().into()))),
                         None,
                     ));
 
-                // Run configurable user function
-
-                Ok(Ctr::None)
-            } else {
-                Err(start_trace(
-                    ("cd", "cannot make absolute path").into()))
+                match syms.call_symbol(
+                    &CD_USER_CB.to_string(),
+                    &Seg::new(),
+                    true,
+                ) {
+                    Ok(r) => {
+                        Ok(*r)
+                    },
+                    Err(s) => {
+                        Err(s.with_trace(("cd", "failed to call callback").into()))
+                    },
+                }
             }
+        },
+        Err(e) => {
+            Err(
+                start_trace(    ("cd", e.to_string()).into())
+                    .with_trace(("cd", "could not make absolute path").into()))
         }
-    } else {
-        Err(start_trace(
-            ("cd", "expected input to be a string")
-                .into()))
     }
 }
 
@@ -948,11 +980,25 @@ pub fn load_posix_shell(syms: &mut SymTable, shell_state: Rc<RefCell<ShellState>
         "cd".to_string(),
         Symbol {
             name: String::from("cd"),
-            args: Args::Strict(vec![Type::String]),
-            conditional_branches: false,
+            args: Args::Lazy(1),
+            conditional_branches: true,
             docs: CD_DOCSTRING.to_string(),
             value: ValueType::Internal(Rc::new(cd_callback)),
             ..Default::default()
         },
     );
+
+    syms.insert(
+        String::from(CD_USER_CB),
+        Symbol {
+            name: String::from(CD_USER_CB),
+            args: Args::None,
+            conditional_branches: false,
+            docs: String::from("lambda called at each invocation of cd"),
+            value: ValueType::Internal(Rc::new(move |_ast: &Seg, _sym: &mut SymTable| -> Result<Ctr, Traceback> {
+                Ok(Ctr::None)
+            })),
+            ..Default::default()
+        },
+    );
 }