5 files changed, 156 insertions, 2 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 5fe64ab..a527d30 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -170,6 +170,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "itoa"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b71991ff56294aa922b450139ee08b3bfc70982c6b2c7562771375cf73542dd4"
+
+[[package]]
 name = "lazy_static"
 version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -184,6 +190,8 @@ dependencies = [
  "macros",
  "rnix",
  "rowan",
+ "serde",
+ "serde_json",
 ]
 
 [[package]]
@@ -330,6 +338,43 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
 
 [[package]]
+name = "ryu"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "71d301d4193d031abdd79ff7e3dd721168a9572ef3fe51a1517aba235bd8f86e"
+
+[[package]]
+name = "serde"
+version = "1.0.130"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f12d06de37cf59146fbdecab66aa99f9fe4f78722e3607577a5375d66bd0c913"
+dependencies = [
+ "serde_derive",
+]
+
+[[package]]
+name = "serde_derive"
+version = "1.0.130"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7bc1a1ab1961464eae040d96713baa5a724a8152c1222492465b54322ec508b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "serde_json"
+version = "1.0.68"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0f690853975602e1bfe1ccbf50504d67174e3bcf340f23b5ea9992e0587a52d8"
+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
+[[package]]
 name = "similar"
 version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -350,6 +395,8 @@ dependencies = [
  "globset",
  "lib",
  "rnix",
+ "serde",
+ "serde_json",
  "similar",
  "thiserror",
  "vfs",
diff --git a/bin/Cargo.toml b/bin/Cargo.toml
index af5a288..528f804 100644
--- a/bin/Cargo.toml
+++ b/bin/Cargo.toml
@@ -14,3 +14,15 @@ thiserror = "1.0.30"
 similar = "2.1.0"
 vfs = { path = "../vfs" }
 lib = { path = "../lib" }
+
+[dependencies.serde_json]
+version = "1.0.68"
+optional = true
+
+[dependencies.serde]
+version = "1.0.68"
+features = [ "derive" ]
+optional = true
+
+[features]
+json = [ "lib/json-out", "serde_json", "serde" ]
diff --git a/bin/src/traits.rs b/bin/src/traits.rs
index 5cf7208..a0e40d4 100644
--- a/bin/src/traits.rs
+++ b/bin/src/traits.rs
@@ -32,9 +32,10 @@ where
         format: OutFormat,
     ) -> io::Result<()> {
         match format {
+            #[cfg(feature = "json")]
+            OutFormat::Json => json::write_json(self, lint_result, vfs),
             OutFormat::StdErr => write_stderr(self, lint_result, vfs),
             OutFormat::Errfmt => write_errfmt(self, lint_result, vfs),
-            _ => Ok(()),
         }
     }
 }
@@ -84,7 +85,11 @@ fn write_stderr<T: Write>(
     Ok(())
 }
 
-fn write_errfmt<T: Write>(writer: &mut T, lint_result: &LintResult, vfs: &ReadOnlyVfs) -> io::Result<()> {
+fn write_errfmt<T: Write>(
+    writer: &mut T,
+    lint_result: &LintResult,
+    vfs: &ReadOnlyVfs,
+) -> io::Result<()> {
     let file_id = lint_result.file_id;
     let src = str::from_utf8(vfs.get(file_id)).unwrap();
     let path = vfs.file_path(file_id);
@@ -107,6 +112,42 @@ fn write_errfmt<T: Write>(writer: &mut T, lint_result: &LintResult, vfs: &ReadOn
     Ok(())
 }
 
+#[cfg(feature = "json")]
+mod json {
+    use crate::lint::LintResult;
+    use std::io::{self, Write};
+    use vfs::ReadOnlyVfs;
+
+    use lib::Report;
+    use serde::Serialize;
+    use serde_json;
+
+    #[derive(Serialize)]
+    struct JsonReport<'μ> {
+        file: &'μ std::path::Path,
+        report: Vec<&'μ Report>,
+    }
+
+    pub fn write_json<T: Write>(
+        writer: &mut T,
+        lint_result: &LintResult,
+        vfs: &ReadOnlyVfs,
+    ) -> io::Result<()> {
+        let file_id = lint_result.file_id;
+        let path = vfs.file_path(file_id);
+        writeln!(
+            writer,
+            "{}",
+            serde_json::to_string_pretty(&JsonReport {
+                file: path,
+                report: lint_result.reports.iter().collect::<Vec<_>>()
+            })
+            .unwrap()
+        )?;
+        Ok(())
+    }
+}
+
 fn line(at: TextRange, src: &str) -> usize {
     let at = at.start().into();
     src[..at].chars().filter(|&c| c == '\n').count() + 1
diff --git a/lib/Cargo.toml b/lib/Cargo.toml
index e9e9e69..e9bca06 100644
--- a/lib/Cargo.toml
+++ b/lib/Cargo.toml
@@ -11,3 +11,13 @@ if_chain = "1.0"
 macros = { path = "../macros" }
 lazy_static = "1.0"
 rowan = "0.12.5"
+serde_json = { version = "1.0.68", optional = true }
+
+[dependencies.serde]
+version = "1.0.130"
+features = [ "derive" ]
+optional = true
+
+[features]
+default = []
+json-out = [ "serde", "serde_json" ]
diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index d8a3859..bde039f 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -6,8 +6,12 @@ pub use lints::LINTS;
 use rnix::{SyntaxElement, SyntaxKind, TextRange};
 use std::{convert::Into, default::Default};
 
+#[cfg(feature = "json-out")]
+use serde::{Serialize, ser::{SerializeStruct, Serializer}};
+
 /// Report generated by a lint
 #[derive(Debug, Default)]
+#[cfg_attr(feature = "json-out", derive(Serialize))]
 pub struct Report {
     /// General information about this lint and where it applies.
     pub note: &'static str,
@@ -95,6 +99,27 @@ impl Diagnostic {
     }
 }
 
+#[cfg(feature = "json-out")]
+impl Serialize for Diagnostic {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut s = serializer.serialize_struct("Diagnostic", 3)?;
+        let at = {
+            let start = usize::from(self.at.start());
+            let end = usize::from(self.at.end());
+            (start, end)
+        };
+        s.serialize_field("at", &at)?;
+        s.serialize_field("message", &self.message)?;
+        if let Some(suggestion) = &self.suggestion {
+            s.serialize_field("suggestion", suggestion)?;
+        }
+        s.end()
+    }
+}
+
 /// Suggested fix for a diagnostic, the fix is provided as a syntax element.
 /// Look at `make.rs` to construct fixes.
 #[derive(Debug)]
@@ -119,6 +144,25 @@ impl Suggestion {
     }
 }
 
+#[cfg(feature = "json-out")]
+impl Serialize for Suggestion {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut s = serializer.serialize_struct("Suggestion", 2)?;
+        let at = {
+            let start = usize::from(self.at.start());
+            let end = usize::from(self.at.end());
+            (start, end)
+        };
+        let fix = self.fix.to_string();
+        s.serialize_field("at", &at)?;
+        s.serialize_field("fix", &fix)?;
+        s.end()
+    }
+}
+
 /// Lint logic is defined via this trait. Do not implement manually,
 /// look at the `lint` attribute macro instead for implementing rules
 pub trait Rule {