avoid parsing TOML twice

flake8_to_ruff/src/main.rs

@@ -18,7 +18,7 @@ use std::path::PathBuf;
 use anyhow::Result;
 use clap::Parser;
 use configparser::ini::Ini;
-use ruff::flake8_to_ruff;
+use ruff::flake8_to_ruff::{self, ExternalConfig};
 
 #[derive(Parser)]
 #[command(
@@ -48,19 +48,20 @@ fn main() -> Result<()> {
     let config = ini.load(cli.file).map_err(|msg| anyhow::anyhow!(msg))?;
 
     // Read the pyproject.toml file.
-    let (black, isort) = match cli.pyproject {
-        Some(path) => {
-            let black = flake8_to_ruff::parse_black_options(&path)?;
-            let isort = flake8_to_ruff::parse_isort_options(&path)?;
-            (black, isort)
-        }
-        None => (None, None),
-    };
-
-    let external_config = flake8_to_ruff::ExternalConfig {
-        black: black.as_ref(),
-        isort: isort.as_ref(),
-    };
+    let pyproject = cli.pyproject.map(flake8_to_ruff::parse).transpose()?;
+    let external_config = pyproject
+        .as_ref()
+        .map(|pyproject| {
+            pyproject
+                .tool
+                .as_ref()
+                .map(|tool| ExternalConfig {
+                    black: tool.black.as_ref(),
+                    isort: tool.isort.as_ref(),
+                })
+                .unwrap_or_default()
+        })
+        .unwrap_or_default();
 
     // Create Ruff's pyproject.toml section.
     let pyproject = flake8_to_ruff::convert(&config, &external_config, cli.plugin)?;

src/flake8_to_ruff/black.rs

@@ -1,11 +1,7 @@
 //! Extract Black configuration settings from a pyproject.toml.
 
-use std::path::Path;
-
-use anyhow::Result;
 use serde::{Deserialize, Serialize};
 
-use super::pyproject::Pyproject;
 use crate::settings::types::PythonVersion;
 
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize, Default)]
@@ -15,10 +11,3 @@ pub struct Black {
     #[serde(alias = "target-version", alias = "target_version")]
     pub target_version: Option<Vec<PythonVersion>>,
 }
-
-pub fn parse_black_options<P: AsRef<Path>>(path: P) -> Result<Option<Black>> {
-    let contents = std::fs::read_to_string(path)?;
-    Ok(toml_edit::easy::from_str::<Pyproject>(&contents)?
-        .tool
-        .and_then(|tool| tool.black))
-}

src/flake8_to_ruff/isort.rs

@@ -1,22 +1,10 @@
 //! Extract isort configuration settings from a pyproject.toml.
 
-use std::path::Path;
-
-use anyhow::Result;
 use serde::{Deserialize, Serialize};
 
-use super::pyproject::Pyproject;
-
 /// The [isort configuration](https://pycqa.github.io/isort/docs/configuration/config_files.html).
 #[derive(Debug, PartialEq, Eq, Serialize, Deserialize, Default)]
 pub struct Isort {
     #[serde(alias = "src-paths", alias = "src_paths")]
     pub src_paths: Option<Vec<String>>,
 }
-
-pub fn parse_isort_options<P: AsRef<Path>>(path: P) -> Result<Option<Isort>> {
-    let contents = std::fs::read_to_string(path)?;
-    Ok(toml_edit::easy::from_str::<Pyproject>(&contents)?
-        .tool
-        .and_then(|tool| tool.isort))
-}

src/flake8_to_ruff/mod.rs

@@ -6,8 +6,7 @@ mod parser;
 mod plugin;
 mod pyproject;
 
-pub use black::parse_black_options;
 pub use converter::convert;
 pub use external_config::ExternalConfig;
-pub use isort::parse_isort_options;
 pub use plugin::Plugin;
+pub use pyproject::parse;

src/flake8_to_ruff/pyproject.rs

@@ -1,3 +1,6 @@
+use std::path::Path;
+
+use anyhow::Result;
 use serde::{Deserialize, Serialize};
 
 use super::black::Black;
@@ -13,3 +16,9 @@ pub struct Tools {
 pub struct Pyproject {
     pub tool: Option<Tools>,
 }
+
+pub fn parse<P: AsRef<Path>>(path: P) -> Result<Pyproject> {
+    let contents = std::fs::read_to_string(path)?;
+    let pyproject = toml_edit::easy::from_str::<Pyproject>(&contents)?;
+    Ok(pyproject)
+}