feat(biome_configuration): add helpers for parsing .editorconfig files

Cargo.toml

@@ -175,6 +175,7 @@ regex              = "1.10.4"
 rustc-hash         = "1.1.0"
 schemars           = { version = "0.8.19", features = ["indexmap2", "smallvec"] }
 serde              = { version = "1.0.201", features = ["derive"] }
+serde_ini          = "0.2.0"
 serde_json         = "1.0.117"
 similar            = "2.5.0"
 slotmap            = "1.0.7"

crates/biome_configuration/Cargo.toml

@@ -36,6 +36,7 @@ oxc_resolver             = { workspace = true }
 rustc-hash               = { workspace = true }
 schemars                 = { workspace = true, features = ["indexmap1"], optional = true }
 serde                    = { workspace = true, features = ["derive"] }
+serde_ini                = { workspace = true }
 serde_json               = { workspace = true, features = ["raw_value"] }
 
 [features]

crates/biome_configuration/src/editorconfig.rs

@@ -0,0 +1,271 @@
+//! Helpers for handling .editorconfig files.
+//!
+//! Here's how the options are mapped to the formatter config:
+//!
+//! | .editorconfig option | biome option |
+//! |----------------------|--------------|
+//! | indent_style         | indent_style |
+//! | indent_size          | indent_width |
+//! | end_of_line          | line_ending  |
+//! | max_line_length      | line_width   |
+
+use std::{collections::HashMap, str::FromStr};
+
+use biome_deserialize::StringSet;
+use biome_diagnostics::Diagnostic;
+use biome_formatter::{LineEnding, LineWidth};
+use indexmap::IndexSet;
+use serde::{Deserialize, Deserializer};
+
+use crate::{
+    OverrideFormatterConfiguration, OverridePattern, Overrides, PartialConfiguration,
+    PartialFormatterConfiguration, PlainIndentStyle,
+};
+
+pub fn parse_str(s: &str) -> serde_ini::de::Result<EditorConfig> {
+    // TODO: use serde_path_to_error to emit better parse diagnostics
+    serde_ini::from_str(s)
+}
+
+/// Represents a parsed .editorconfig file, containing only the options that are relevant to biome.
+#[derive(Debug, Clone, Deserialize, Default)]
+#[serde(default)]
+pub struct EditorConfig {
+    #[serde(deserialize_with = "deserialize_bool_from_string")]
+    root: bool,
+    #[serde(flatten)]
+    options: HashMap<String, EditorConfigOptions>,
+}
+
+impl EditorConfig {
+    pub fn to_biome(
+        mut self,
+    ) -> (
+        Option<PartialConfiguration>,
+        Vec<EditorConfigValidationError>,
+    ) {
+        let diagnostics = self.validate();
+
+        let mut config = PartialConfiguration {
+            formatter: self.options.remove("*").map(|o| o.to_biome()),
+            ..Default::default()
+        };
+        let overrides: Vec<_> = self
+            .options
+            .into_iter()
+            .map(|(k, v)| OverridePattern {
+                include: Some(StringSet::new(IndexSet::from([k]))),
+                formatter: Some(v.to_biome_override()),
+                ..Default::default()
+            })
+            .collect();
+        config.overrides = Some(Overrides(overrides));
+
+        (Some(config), diagnostics)
+    }
+
+    fn validate(&self) -> Vec<EditorConfigValidationError> {
+        self.options.values().flat_map(|o| o.validate()).collect()
+    }
+}
+
+#[derive(Debug, Clone, Deserialize, Default)]
+#[serde(default)]
+pub struct EditorConfigOptions {
+    indent_style: Option<PlainIndentStyle>,
+    #[serde(deserialize_with = "deserialize_optional_u8_from_string")]
+    indent_size: Option<u8>,
+    end_of_line: Option<LineEnding>,
+    #[serde(deserialize_with = "deserialize_optional_line_width_from_string")]
+    max_line_length: Option<LineWidth>,
+    // Not a biome option, but we need it to emit a diagnostic when this is set to false.
+    #[serde(deserialize_with = "deserialize_optional_bool_from_string")]
+    insert_final_newline: Option<bool>,
+}
+
+impl EditorConfigOptions {
+    pub fn to_biome(self) -> PartialFormatterConfiguration {
+        PartialFormatterConfiguration {
+            indent_style: self.indent_style,
+            indent_width: self.indent_size,
+            line_ending: self.end_of_line,
+            line_width: self.max_line_length,
+            ..Default::default()
+        }
+    }
+
+    pub fn to_biome_override(self) -> OverrideFormatterConfiguration {
+        OverrideFormatterConfiguration {
+            indent_style: self.indent_style,
+            indent_width: self.indent_size,
+            line_ending: self.end_of_line,
+            line_width: self.max_line_length,
+            ..Default::default()
+        }
+    }
+
+    fn validate(&self) -> Vec<EditorConfigValidationError> {
+        let mut errors = vec![];
+        // `insert_final_newline = false` results in formatting behavior that is incompatible with biome
+        if let Some(false) = self.insert_final_newline {
+            errors.push(EditorConfigValidationError::Incompatible {
+                key: "insert_final_newline",
+                message: "Biome always inserts a final newline.",
+            });
+        }
+        errors
+    }
+}
+
+fn deserialize_bool_from_string<'de, D>(deserializer: D) -> Result<bool, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let s = String::deserialize(deserializer)?;
+    match s.as_str() {
+        "false" => Ok(false),
+        "true" => Ok(true),
+        _ => Err(serde::de::Error::custom("expected 'true' or 'false'")),
+    }
+}
+
+fn deserialize_optional_bool_from_string<'de, D>(deserializer: D) -> Result<Option<bool>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    deserialize_bool_from_string(deserializer).map(Some)
+}
+
+fn deserialize_optional_u8_from_string<'de, D>(deserializer: D) -> Result<Option<u8>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let s = String::deserialize(deserializer)?;
+    match s.parse() {
+        Ok(n) => Ok(Some(n)),
+        Err(_) => Err(serde::de::Error::custom(
+            "expected a number between 0 and 255",
+        )),
+    }
+}
+
+fn deserialize_optional_line_width_from_string<'de, D>(
+    deserializer: D,
+) -> Result<Option<LineWidth>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let s = String::deserialize(deserializer)?;
+    LineWidth::from_str(s.as_str())
+        .map_err(serde::de::Error::custom)
+        .map(Some)
+}
+
+#[derive(Debug, Clone)]
+pub enum EditorConfigValidationError {
+    Incompatible {
+        key: &'static str,
+        message: &'static str,
+    },
+}
+
+impl Diagnostic for EditorConfigValidationError {
+    fn severity(&self) -> biome_diagnostics::Severity {
+        biome_diagnostics::Severity::Error
+    }
+
+    fn description(&self, fmt: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(fmt, "editorconfig validation error: ")?;
+        match self {
+            EditorConfigValidationError::Incompatible { key, message } => {
+                write!(fmt, "key '{}' is incompatible with biome: {}", key, message)?;
+            }
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn should_parse_editorconfig() {
+        // the example from https://editorconfig.org/
+        let input = r#"
+# EditorConfig is awesome: https://EditorConfig.org
+
+# top-most EditorConfig file
+root = true
+
+# Unix-style newlines with a newline ending every file
+[*]
+end_of_line = lf
+insert_final_newline = true
+
+# Matches multiple files with brace expansion notation
+# Set default charset
+[*.{js,py}]
+charset = utf-8
+
+# 4 space indentation
+[*.py]
+indent_style = space
+indent_size = 4
+
+# Tab indentation (no size specified)
+[Makefile]
+indent_style = tab
+
+# Indentation override for all JS under lib directory
+[lib/**.js]
+indent_style = space
+indent_size = 2
+
+# Matches the exact files either package.json or .travis.yml
+[{package.json,.travis.yml}]
+indent_style = space
+indent_size = 2
+"#;
+
+        let conf = parse_str(input).expect("Failed to parse editorconfig");
+        assert!(conf.root);
+    }
+
+    #[test]
+    fn should_convert_to_biome_root_settings() {
+        let input = r#"
+root = true
+
+[*]
+insert_final_newline = true
+end_of_line = lf
+indent_style = tab
+indent_size = 4
+max_line_length = 120
+"#;
+
+        let conf = parse_str(input).expect("Failed to parse editorconfig");
+        let (conf, _) = conf.to_biome();
+        let conf = conf.expect("Failed to convert editorconfig to biome");
+        let formatter = conf.formatter.expect("Formatter not set");
+        assert_eq!(formatter.indent_style, Some(PlainIndentStyle::Tab));
+        assert_eq!(formatter.indent_width, Some(4));
+        assert_eq!(formatter.line_ending, Some(LineEnding::Lf));
+        assert_eq!(formatter.line_width.map(|v| v.get()), Some(120));
+    }
+
+    #[test]
+    fn should_emit_diagnostic() {
+        let input = r#"
+root = true
+
+[*]
+insert_final_newline = false
+"#;
+
+        let conf = parse_str(input).expect("Failed to parse editorconfig");
+        let (_, errors) = conf.to_biome();
+        assert_eq!(errors.len(), 1);
+    }
+}

crates/biome_configuration/src/lib.rs

@@ -4,6 +4,7 @@
 //! by language. The language might further options divided by tool.
 pub mod css;
 pub mod diagnostics;
+pub mod editorconfig;
 pub mod formatter;
 pub mod generated;
 pub mod javascript;

crates/biome_formatter/src/lib.rs

@@ -277,6 +277,11 @@ impl<'de> serde::Deserialize<'de> for LineWidth {
     where
         D: serde::Deserializer<'de>,
     {
+        // if let Ok(string_value) = <String as serde::Deserialize>::deserialize(&deserializer) {
+        //     if let Ok(value) = u16::from_str(&string_value) {
+        //         return LineWidth::try_from(value).map_err(serde::de::Error::custom);
+        //     }
+        // }
         let value: u16 = serde::Deserialize::deserialize(deserializer)?;
         let line_width = LineWidth::try_from(value).map_err(serde::de::Error::custom)?;
         Ok(line_width)