add reflow command

book/src/generated/typable-cmd.md

@@ -58,6 +58,7 @@
 | `:set-option`, `:set` | Set a config option at runtime |
 | `:sort` | Sort ranges in selection. |
 | `:rsort` | Sort ranges in selection in reverse order. |
+| `:reflow` | Hard-wrap the current selection of lines to a given width. |
 | `:tree-sitter-subtree`, `:ts-subtree` | Display tree sitter subtree under cursor, primarily for debugging queries. |
 | `:config-reload` | Refreshes helix's config. |
 | `:config-open` | Open the helix config.toml file. |

helix-core/Cargo.toml

@@ -41,6 +41,7 @@ encoding_rs = "0.8"
 chrono = { version = "0.4", default-features = false, features = ["alloc", "std"] }
 
 etcetera = "0.3"
+textwrap = "0.15.0"
 
 [dev-dependencies]
 quickcheck = { version = "1", default-features = false }

helix-core/src/lib.rs

@@ -27,6 +27,7 @@ pub mod syntax;
 pub mod test;
 pub mod textobject;
 mod transaction;
+pub mod wrap;
 
 pub mod unicode {
     pub use unicode_general_category as category;

helix-core/src/syntax.rs

@@ -67,6 +67,7 @@ pub struct LanguageConfiguration {
     pub shebangs: Vec<String>, // interpreter(s) associated with language
     pub roots: Vec<String>,      // these indicate project roots <.git, Cargo.toml>
     pub comment_token: Option<String>,
+    pub max_line_length: Option<usize>,
 
     #[serde(default, skip_serializing, deserialize_with = "deserialize_lsp_config")]
     pub config: Option<serde_json::Value>,

helix-core/src/wrap.rs

@@ -0,0 +1,7 @@
+use smartstring::{LazyCompact, SmartString};
+
+/// Given a slice of text, return the text re-wrapped to fit it
+/// within the given width.
+pub fn reflow_hard_wrap(text: &str, max_line_len: usize) -> SmartString<LazyCompact> {
+    textwrap::refill(text, max_line_len).into()
+}

helix-term/src/commands/typed.rs

@@ -1012,6 +1012,45 @@ fn sort_impl(
     Ok(())
 }
 
+fn reflow(
+    cx: &mut compositor::Context,
+    args: &[Cow<str>],
+    _event: PromptEvent,
+) -> anyhow::Result<()> {
+    let (view, doc) = current!(cx.editor);
+
+    const DEFAULT_MAX_LEN: usize = 79;
+
+    // Find the max line length by checking the following sources in order:
+    //   - The passed argument in `args`
+    //   - The configured max_line_len for this language in languages.toml
+    //   - The const default we set above
+    let max_line_len: usize = args
+        .get(0)
+        .map(|num| num.parse::<usize>())
+        .transpose()?
+        .or_else(|| {
+            doc.language_config()
+                .and_then(|config| config.max_line_length)
+        })
+        .unwrap_or(DEFAULT_MAX_LEN);
+
+    let rope = doc.text();
+
+    let selection = doc.selection(view.id);
+    let transaction = Transaction::change_by_selection(rope, selection, |range| {
+        let fragment = range.fragment(rope.slice(..));
+        let reflowed_text = helix_core::wrap::reflow_hard_wrap(&fragment, max_line_len);
+
+        (range.from(), range.to(), Some(reflowed_text))
+    });
+
+    doc.apply(&transaction, view.id);
+    doc.append_changes_to_history(view.id);
+
+    Ok(())
+}
+
 fn tree_sitter_subtree(
     cx: &mut compositor::Context,
     _args: &[Cow<str>],
@@ -1474,6 +1513,13 @@ pub const TYPABLE_COMMAND_LIST: &[TypableCommand] = &[
             fun: sort_reverse,
             completer: None,
         },
+        TypableCommand {
+            name: "reflow",
+            aliases: &[],
+            doc: "Hard-wrap the current selection of lines to a given width.",
+            fun: reflow,
+            completer: None,
+        },
         TypableCommand {
             name: "tree-sitter-subtree",
             aliases: &["ts-subtree"],