From e8c955da4cbb042e6f9b89307d143f5bfa6779fa Mon Sep 17 00:00:00 2001
From: Akshay <nerdy@peppe.rs>
Date: Sun, 31 Oct 2021 14:35:26 +0530
Subject: add `explain` subcommand and explanations to all lints

---
 bin/src/config.rs  | 24 ++++++++++++++++++++++++
 bin/src/err.rs     | 10 ++++++++++
 bin/src/explain.rs | 15 +++++++++++++++
 bin/src/main.rs    |  5 +++++
 4 files changed, 54 insertions(+)
 create mode 100644 bin/src/explain.rs

(limited to 'bin')

diff --git a/bin/src/config.rs b/bin/src/config.rs
index ef3a29d..1649017 100644
--- a/bin/src/config.rs
+++ b/bin/src/config.rs
@@ -26,6 +26,8 @@ pub enum SubCommand {
     Fix(Fix),
     /// Fix exactly one issue at provided position
     Single(Single),
+    /// Print detailed explanation for a lint warning
+    Explain(Explain),
 }
 
 #[derive(Clap, Debug)]
@@ -88,6 +90,13 @@ pub struct Single {
     pub diff_only: bool,
 }
 
+#[derive(Clap, Debug)]
+pub struct Explain {
+    /// Warning code to explain
+    #[clap(parse(try_from_str = parse_warning_code))]
+    pub target: u32,
+}
+
 mod dirs {
     use std::{
         fs,
@@ -160,6 +169,21 @@ fn parse_line_col(src: &str) -> Result<(usize, usize), ConfigErr> {
     }
 }
 
+fn parse_warning_code(src: &str) -> Result<u32, ConfigErr> {
+    let mut char_stream = src.chars();
+    let severity = char_stream
+        .next()
+        .ok_or(ConfigErr::InvalidWarningCode(src.to_owned()))?
+        .to_ascii_lowercase();
+    match severity {
+        'w' => char_stream
+            .collect::<String>()
+            .parse::<u32>()
+            .map_err(|_| ConfigErr::InvalidWarningCode(src.to_owned())),
+        _ => Ok(0),
+    }
+}
+
 fn build_ignore_set(ignores: &[String]) -> Result<GlobSet, GlobError> {
     let mut set = GlobSetBuilder::new();
     for pattern in ignores {
diff --git a/bin/src/err.rs b/bin/src/err.rs
index 4c16d69..1e52c2b 100644
--- a/bin/src/err.rs
+++ b/bin/src/err.rs
@@ -12,6 +12,8 @@ pub enum ConfigErr {
     InvalidPath(#[from] io::Error),
     #[error("unable to parse `{0}` as line and column")]
     InvalidPosition(String),
+    #[error("unable to parse `{0}` as warning code")]
+    InvalidWarningCode(String),
 }
 
 // #[derive(Error, Debug)]
@@ -40,6 +42,12 @@ pub enum SingleFixErr {
     NoOp,
 }
 
+#[derive(Error, Debug)]
+pub enum ExplainErr {
+    #[error("lint with code `{0}` not found")]
+    LintNotFound(u32),
+}
+
 #[derive(Error, Debug)]
 pub enum StatixErr {
     // #[error("linter error: {0}")]
@@ -50,4 +58,6 @@ pub enum StatixErr {
     Single(#[from] SingleFixErr),
     #[error("config error: {0}")]
     Config(#[from] ConfigErr),
+    #[error("explain error: {0}")]
+    Explain(#[from] ExplainErr),
 }
diff --git a/bin/src/explain.rs b/bin/src/explain.rs
new file mode 100644
index 0000000..6aefa7e
--- /dev/null
+++ b/bin/src/explain.rs
@@ -0,0 +1,15 @@
+use crate::err::ExplainErr;
+
+use lib::LINTS;
+
+pub fn explain(code: u32) -> Result<&'static str, ExplainErr> {
+    match code {
+        0 => Ok("syntax error"),
+        _ => LINTS
+            .values()
+            .flatten()
+            .find(|l| l.code() == code)
+            .map(|l| l.explanation())
+            .ok_or(ExplainErr::LintNotFound(code)),
+    }
+}
diff --git a/bin/src/main.rs b/bin/src/main.rs
index 90b79ce..31f6823 100644
--- a/bin/src/main.rs
+++ b/bin/src/main.rs
@@ -1,5 +1,6 @@
 mod config;
 mod err;
+mod explain;
 mod fix;
 mod lint;
 mod traits;
@@ -86,6 +87,10 @@ fn _main() -> Result<(), StatixErr> {
                 print!("{}", &*single_fix_result.src)
             }
         }
+        SubCommand::Explain(explain_config) => {
+            let explanation = explain::explain(explain_config.target)?;
+            println!("{}", explanation)
+        }
     }
     Ok(())
 }
-- 
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