feat(fmt): Configurable autoformat with `FormatConfig` (#95)

Fixes: https://github.com/kdl-org/kdl-rs/issues/85

src/document.rs

@@ -2,7 +2,7 @@
 use miette::SourceSpan;
 use std::fmt::Display;
 
-use crate::{KdlNode, KdlParseFailure, KdlValue};
+use crate::{FormatConfig, KdlNode, KdlParseFailure, KdlValue};
 
 /// Represents a KDL
 /// [`Document`](https://github.com/kdl-org/kdl/blob/main/SPEC.md#document).
@@ -232,12 +232,33 @@ impl KdlDocument {
     /// Auto-formats this Document, making everything nice while preserving
     /// comments.
     pub fn autoformat(&mut self) {
-        self.autoformat_impl(0, false);
+        self.autoformat_config(&FormatConfig::default());
     }
 
     /// Formats the document and removes all comments from the document.
     pub fn autoformat_no_comments(&mut self) {
-        self.autoformat_impl(0, true);
+        self.autoformat_config(&FormatConfig {
+            no_comments: true,
+            ..Default::default()
+        });
+    }
+
+    /// Formats the document according to `config`.
+    pub fn autoformat_config(&mut self, config: &FormatConfig<'_>) {
+        if let Some(KdlDocumentFormat { leading, .. }) = (&mut *self).format_mut() {
+            crate::fmt::autoformat_leading(leading, config);
+        }
+        let mut has_nodes = false;
+        for node in &mut (&mut *self).nodes {
+            has_nodes = true;
+            node.autoformat_config(config);
+        }
+        if let Some(KdlDocumentFormat { trailing, .. }) = (&mut *self).format_mut() {
+            crate::fmt::autoformat_trailing(trailing, config.no_comments);
+            if !has_nodes {
+                trailing.push('\n');
+            }
+        };
     }
 
     // TODO(@zkat): These should all be moved into the query module itself,
@@ -326,23 +347,6 @@ impl Display for KdlDocument {
 }
 
 impl KdlDocument {
-    pub(crate) fn autoformat_impl(&mut self, indent: usize, no_comments: bool) {
-        if let Some(KdlDocumentFormat { leading, .. }) = self.format_mut() {
-            crate::fmt::autoformat_leading(leading, indent, no_comments);
-        }
-        let mut has_nodes = false;
-        for node in &mut self.nodes {
-            has_nodes = true;
-            node.autoformat_impl(indent, no_comments);
-        }
-        if let Some(KdlDocumentFormat { trailing, .. }) = self.format_mut() {
-            crate::fmt::autoformat_trailing(trailing, no_comments);
-            if !has_nodes {
-                trailing.push('\n');
-            }
-        }
-    }
-
     pub(crate) fn stringify(
         &self,
         f: &mut std::fmt::Formatter<'_>,
@@ -648,6 +652,65 @@ foo 1 bar=0xdeadbeef {
         Ok(())
     }
 
+    #[test]
+    fn simple_autoformat_two_spaces() -> miette::Result<()> {
+        let mut doc: KdlDocument = "a { b { c { }; }; }".parse().unwrap();
+        KdlDocument::autoformat_config(
+            &mut doc,
+            &FormatConfig {
+                indent: "  ",
+                ..Default::default()
+            },
+        );
+        assert_eq!(
+            doc.to_string(),
+            r#"a {
+  b {
+    c {
+
+    }
+  }
+}
+"#
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn simple_autoformat_single_tabs() -> miette::Result<()> {
+        let mut doc: KdlDocument = "a { b { c { }; }; }".parse().unwrap();
+        KdlDocument::autoformat_config(
+            &mut doc,
+            &FormatConfig {
+                indent: "\t",
+                ..Default::default()
+            },
+        );
+        assert_eq!(doc.to_string(), "a {\n\tb {\n\t\tc {\n\n\t\t}\n\t}\n}\n");
+        Ok(())
+    }
+
+    #[test]
+    fn simple_autoformat_no_comments() -> miette::Result<()> {
+        let mut doc: KdlDocument =
+            "// a comment\na {\n// another comment\n b { c { // another comment\n }; }; }"
+                .parse()
+                .unwrap();
+        KdlDocument::autoformat_no_comments(&mut doc);
+        assert_eq!(
+            doc.to_string(),
+            r#"a {
+    b {
+        c {
+
+        }
+    }
+}
+"#
+        );
+        Ok(())
+    }
+
     #[cfg(feature = "span")]
     fn check_spans_for_doc(doc: &KdlDocument, source: &impl miette::SourceCode) {
         for node in doc.nodes() {

src/fmt.rs

@@ -1,19 +1,131 @@
 use std::fmt::Write as _;
 
-pub(crate) fn autoformat_leading(leading: &mut String, indent: usize, no_comments: bool) {
+/// Formatting configuration for use with [`KdlDocument::autoformat_config`](`crate::KdlDocument::autoformat_config`)
+/// and [`KdlNode::autoformat_config`](`crate::KdlNode::autoformat_config`).
+#[non_exhaustive]
+#[derive(Debug)]
+pub struct FormatConfig<'a> {
+    /// How deeply to indent the overall node or document,
+    /// in repetitions of [`indent`](`FormatConfig::indent`).
+    /// Defaults to `0`.
+    pub indent_level: usize,
+
+    /// The indentation to use at each level. Defaults to four spaces.
+    pub indent: &'a str,
+
+    /// Whether to remove comments. Defaults to `false`.
+    pub no_comments: bool,
+}
+
+/// See field documentation for defaults.
+impl Default for FormatConfig<'_> {
+    fn default() -> Self {
+        Self::builder().build()
+    }
+}
+
+impl FormatConfig<'_> {
+    /// Creates a new [`FormatConfigBuilder`] with default configuration.
+    pub const fn builder() -> FormatConfigBuilder<'static> {
+        FormatConfigBuilder::new()
+    }
+}
+
+/// A [`FormatConfig`] builder.
+///
+/// Note that setters can be repeated.
+#[derive(Debug, Default)]
+pub struct FormatConfigBuilder<'a>(FormatConfig<'a>);
+
+impl<'a> FormatConfigBuilder<'a> {
+    /// Creates a new [`FormatConfig`] builder with default configuration.
+    pub const fn new() -> Self {
+        FormatConfigBuilder(FormatConfig {
+            indent_level: 0,
+            indent: "    ",
+            no_comments: false,
+        })
+    }
+
+    /// How deeply to indent the overall node or document,
+    /// in repetitions of [`indent`](`FormatConfig::indent`).
+    /// Defaults to `0` iff not specified.
+    pub const fn maybe_indent_level(mut self, indent_level: Option<usize>) -> Self {
+        if let Some(indent_level) = indent_level {
+            self.0.indent_level = indent_level;
+        }
+        self
+    }
+
+    /// How deeply to indent the overall node or document,
+    /// in repetitions of [`indent`](`FormatConfig::indent`).
+    /// Defaults to `0` iff not specified.
+    pub const fn indent_level(mut self, indent_level: usize) -> Self {
+        self.0.indent_level = indent_level;
+        self
+    }
+
+    /// The indentation to use at each level.
+    /// Defaults to four spaces iff not specified.
+    pub const fn maybe_indent<'b, 'c>(self, indent: Option<&'b str>) -> FormatConfigBuilder<'c>
+    where
+        'a: 'b,
+        'b: 'c,
+    {
+        if let Some(indent) = indent {
+            self.indent(indent)
+        } else {
+            self
+        }
+    }
+
+    /// The indentation to use at each level.
+    /// Defaults to four spaces if not specified.
+    pub const fn indent<'b>(self, indent: &'b str) -> FormatConfigBuilder<'b> {
+        FormatConfigBuilder(FormatConfig { indent, ..self.0 })
+    }
+
+    /// Whether to remove comments.
+    /// Defaults to `false` iff not specified.
+    pub const fn maybe_no_comments(mut self, no_comments: Option<bool>) -> Self {
+        if let Some(no_comments) = no_comments {
+            self.0.no_comments = no_comments;
+        }
+        self
+    }
+
+    /// Whether to remove comments.
+    /// Defaults to `false` iff not specified.
+    pub const fn no_comments(mut self, no_comments: bool) -> Self {
+        self.0.no_comments = no_comments;
+        self
+    }
+
+    /// Builds the [`FormatConfig`].
+    pub const fn build(self) -> FormatConfig<'a> {
+        self.0
+    }
+}
+
+pub(crate) fn autoformat_leading(leading: &mut String, config: &FormatConfig<'_>) {
     let mut result = String::new();
-    if !no_comments {
+    if !config.no_comments {
         let input = leading.trim();
         if !input.is_empty() {
             for line in input.lines() {
                 let trimmed = line.trim();
                 if !trimmed.is_empty() {
-                    writeln!(result, "{:indent$}{}", "", trimmed, indent = indent).unwrap();
+                    for _ in 0..config.indent_level {
+                        result.push_str(config.indent);
+                    }
+                    writeln!(result, "{}", trimmed).unwrap();
                 }
             }
         }
     }
-    write!(result, "{:indent$}", "", indent = indent).unwrap();
+    for _ in 0..config.indent_level {
+        result.push_str(config.indent);
+    }
     *leading = result;
 }
 
@@ -33,3 +145,26 @@ pub(crate) fn autoformat_trailing(decor: &mut String, no_comments: bool) {
     }
     *decor = result;
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn builder() -> miette::Result<()> {
+        let built = FormatConfig::builder()
+            .indent_level(12)
+            .indent(" \t")
+            .no_comments(true)
+            .build();
+        assert!(matches!(
+            built,
+            FormatConfig {
+                indent_level: 12,
+                indent: " \t",
+                no_comments: true,
+            }
+        ));
+        Ok(())
+    }
+}

src/lib.rs

@@ -175,6 +175,7 @@
 pub use document::*;
 pub use entry::*;
 pub use error::*;
+pub use fmt::*;
 pub use identifier::*;
 pub use node::*;
 // pub use query::*;

src/node.rs

@@ -8,11 +8,10 @@ use std::{
 use miette::SourceSpan;
 
 use crate::{
-    v2_parser, KdlDocument, KdlDocumentFormat, KdlEntry, KdlIdentifier, KdlParseFailure, KdlValue,
+    v2_parser, FormatConfig, KdlDocument, KdlDocumentFormat, KdlEntry, KdlIdentifier,
+    KdlParseFailure, KdlValue,
 };
 
-static INDENT: usize = 4;
-
 /// Represents an individual KDL
 /// [`Node`](https://github.com/kdl-org/kdl/blob/main/SPEC.md#node) inside a
 /// KDL Document.
@@ -388,12 +387,68 @@ impl KdlNode {
     }
     /// Auto-formats this node and its contents.
     pub fn autoformat(&mut self) {
-        self.autoformat_impl(0, false);
+        self.autoformat_config(&FormatConfig::default());
     }
 
     /// Auto-formats this node and its contents, stripping comments.
     pub fn autoformat_no_comments(&mut self) {
-        self.autoformat_impl(0, true);
+        self.autoformat_config(&FormatConfig {
+            no_comments: true,
+            ..Default::default()
+        });
+    }
+
+    /// Auto-formats this node and its contents according to `config`.
+    pub fn autoformat_config(&mut self, config: &FormatConfig<'_>) {
+        if let Some(KdlNodeFormat {
+            leading,
+            before_terminator,
+            terminator,
+            trailing,
+            before_children,
+            ..
+        }) = self.format_mut()
+        {
+            crate::fmt::autoformat_leading(leading, config);
+            crate::fmt::autoformat_trailing(before_terminator, config.no_comments);
+            crate::fmt::autoformat_trailing(trailing, config.no_comments);
+            *trailing = trailing.trim().into();
+            if !terminator.starts_with('\n') {
+                *terminator = "\n".into();
+            }
+            if let Some(c) = trailing.chars().next() {
+                if !c.is_whitespace() {
+                    trailing.insert(0, ' ');
+                }
+            }
+
+            *before_children = " ".into();
+        } else {
+            self.set_format(KdlNodeFormat {
+                terminator: "\n".into(),
+                ..Default::default()
+            })
+        }
+        self.name.clear_format();
+        if let Some(ty) = self.ty.as_mut() {
+            ty.clear_format()
+        }
+        for entry in &mut self.entries {
+            entry.autoformat();
+        }
+        if let Some(children) = self.children.as_mut() {
+            children.autoformat_config(&FormatConfig {
+                indent_level: config.indent_level + 1,
+                ..*config
+            });
+            if let Some(KdlDocumentFormat { leading, trailing }) = children.format_mut() {
+                *leading = leading.trim().into();
+                leading.push('\n');
+                for _ in 0..config.indent_level {
+                    trailing.push_str(config.indent);
+                }
+            }
+        }
     }
 
     // TODO(@zkat): These should all be moved into the query module, instead
@@ -512,53 +567,6 @@ impl Display for KdlNode {
 }
 
 impl KdlNode {
-    pub(crate) fn autoformat_impl(&mut self, indent: usize, no_comments: bool) {
-        if let Some(KdlNodeFormat {
-            leading,
-            before_terminator,
-            terminator,
-            trailing,
-            before_children,
-            ..
-        }) = self.format_mut()
-        {
-            crate::fmt::autoformat_leading(leading, indent, no_comments);
-            crate::fmt::autoformat_trailing(before_terminator, no_comments);
-            crate::fmt::autoformat_trailing(trailing, no_comments);
-            *trailing = trailing.trim().into();
-            if !terminator.starts_with('\n') {
-                *terminator = "\n".into();
-            }
-            if let Some(c) = trailing.chars().next() {
-                if !c.is_whitespace() {
-                    trailing.insert(0, ' ');
-                }
-            }
-
-            *before_children = " ".into();
-        } else {
-            self.set_format(KdlNodeFormat {
-                terminator: "\n".into(),
-                ..Default::default()
-            })
-        }
-        self.name.clear_format();
-        if let Some(ty) = self.ty.as_mut() {
-            ty.clear_format()
-        }
-        for entry in &mut self.entries {
-            entry.autoformat();
-        }
-        if let Some(children) = self.children.as_mut() {
-            children.autoformat_impl(indent + INDENT, no_comments);
-            if let Some(KdlDocumentFormat { leading, trailing }) = children.format_mut() {
-                *leading = leading.trim().into();
-                leading.push('\n');
-                trailing.push_str(format!("{:indent$}", "", indent = indent).as_str());
-            }
-        }
-    }
-
     pub(crate) fn stringify(
         &self,
         f: &mut std::fmt::Formatter<'_>,