implement rudimentary bash completion

complete/src/bash.rs

@@ -0,0 +1,64 @@
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use crate::{Command, Flag};
+
+/// Create completion script for `bash`
+///
+/// Short and long options are combined into single `complete` calls, even if
+/// they differ in whether they take arguments or not; just like in case of `fish`.
+/// Also, pretend that files are fine in any position. ValueHints are ignored entirely.
+pub fn render(c: &Command) -> String {
+    let mut out = String::new();
+    let name = &c.name;
+    // Register _comp_uu_FOO as a bash function that computes completions:
+    out.push_str(&format!("complete -F _comp_uu_{name} {name};"));
+    out.push_str(&format!("_comp_uu_{name}()"));
+    // Unless the current argument starts with "-", pre-populate the completions list with all files and dirs:
+    out.push_str("{ local cur;_init_completion||return;COMPREPLY=();if [[ \"$cur\" != \"-*\" ]]; then _filedir;fi;COMPREPLY+=($(compgen -W \"");
+    for arg in &c.args {
+        for Flag { flag, .. } in &arg.short {
+            out.push_str(&format!("-{flag} "));
+        }
+        for Flag { flag, .. } in &arg.long {
+            out.push_str(&format!("--{flag} "));
+        }
+    }
+    out.push_str("\" -- \"$cur\"));}\n");
+    out
+}
+
+#[cfg(test)]
+mod test {
+    use super::render;
+    use crate::{Arg, Command, Flag, Value};
+
+    #[test]
+    fn simple() {
+        let c = Command {
+            name: "foo",
+            args: vec![
+                Arg {
+                    short: vec![Flag {
+                        flag: "a",
+                        value: Value::No,
+                    }],
+                    long: vec![Flag {
+                        flag: "all",
+                        value: Value::No,
+                    }],
+                    ..Arg::default()
+                },
+                Arg {
+                    short: vec![Flag {
+                        flag: "x",
+                        value: Value::No,
+                    }],
+                    ..Arg::default()
+                },
+            ],
+            ..Command::default()
+        };
+        assert_eq!(render(&c), "complete -F _comp_uu_foo foo;_comp_uu_foo(){ local cur;_init_completion||return;COMPREPLY=();if [[ \"$cur\" != \"-*\" ]]; then _filedir;fi;COMPREPLY+=($(compgen -W \"-a --all -x \" -- \"$cur\"));}\n")
+    }
+}

complete/src/lib.rs

@@ -13,6 +13,7 @@
 //!  - Some information is removed because it is irrelevant for completion and documentation
 //!  - This struct is meant to exist at runtime of the program
 //!
+mod bash;
 mod fish;
 mod man;
 mod md;
@@ -75,7 +76,8 @@ pub fn render(c: &Command, shell: &str) -> String {
         "zsh" => zsh::render(c),
         "nu" | "nushell" => nu::render(c),
         "man" => man::render(c),
-        "sh" | "bash" | "csh" | "elvish" | "powershell" => panic!("shell '{shell}' completion is not implemented yet!"),
+        "bash" => bash::render(c),
+        "sh" | "csh" | "elvish" | "powershell" => panic!("shell '{shell}' completion is not implemented yet!"),
         _ => panic!("unknown option '{shell}'! Expected one of: \"md\", \"fish\", \"zsh\", \"nu[shell]\", \"man\", \"sh\", \"bash\", \"csh\", \"elvish\", \"powershell\""),
     }
 }