Load error codes via build script instead of JSON parsing

This scans the tree for `error_codes.rs` and loads all of them.

Cargo.lock

@@ -946,6 +946,7 @@ name = "error_index_generator"
 version = "0.0.0"
 dependencies = [
  "rustdoc",
+ "walkdir",
 ]
 
 [[package]]

src/tools/error_index_generator/Cargo.toml

@@ -3,10 +3,14 @@ authors = ["The Rust Project Developers"]
 name = "error_index_generator"
 version = "0.0.0"
 edition = "2018"
+build = "build.rs"
 
 [dependencies]
 rustdoc = { path = "../../librustdoc" }
 
+[build-dependencies]
+walkdir = "2"
+
 [[bin]]
 name = "error_index_generator"
 path = "main.rs"

src/tools/error_index_generator/build.rs

@@ -0,0 +1,64 @@
+use walkdir::WalkDir;
+use std::path::PathBuf;
+use std::{env, fs};
+
+fn main() {
+    // The src directory (we are in src/tools/error_index_generator)
+    // Note that we could skip one of the .. but this ensures we at least loosely find the right
+    // directory.
+    let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
+    let dest = out_dir.join("error_codes.rs");
+    let mut idx = 0;
+    for entry in WalkDir::new("../../../src") {
+        let entry = entry.unwrap();
+        if entry.file_name() == "error_codes.rs" {
+            println!("cargo:rerun-if-changed={}", entry.path().to_str().unwrap());
+            let file = fs::read_to_string(entry.path()).unwrap()
+                .replace("use syntax::{register_diagnostics, register_long_diagnostics};", "")
+                .replace("use syntax::register_diagnostics;", "")
+                .replace("use syntax::register_long_diagnostics;", "");
+            let contents = format!("(|| {{\n{}\n}})();", file);
+
+            fs::write(&out_dir.join(&format!("error_{}.rs", idx)), &contents).unwrap();
+
+            idx += 1;
+        }
+    }
+
+    let mut all = String::new();
+    all.push_str("fn register_all() -> Vec<(&'static str, Option<&'static str>)> {\n");
+    all.push_str("let mut long_codes: Vec<(&'static str, Option<&'static str>)> = Vec::new();\n");
+    all.push_str(r#"
+macro_rules! register_diagnostics {
+    ($($code:tt),*) => {{
+        long_codes.extend([$(
+            stringify!($code),
+        )*].iter().cloned().map(|s| (s, None)).collect::<Vec<_>>());
+    }};
+    ($($code:tt),*,) => {{
+        long_codes.extend([$(
+            stringify!($code),
+        )*].iter().cloned().map(|s| (s, None)));
+    }}
+}
+
+macro_rules! register_long_diagnostics {
+    ($($code:tt: $description:tt),*) => {
+        {long_codes.extend([$(
+            (stringify!($code), Some(stringify!($description))),
+        )*].iter());}
+    };
+    ($($code:tt: $description:tt),*,) => {
+        {long_codes.extend([$(
+            (stringify!($code), Some(stringify!($description))),
+        )*].iter());}
+    }
+}"#);
+    for idx in 0..idx {
+        all.push_str(&format!(r#"include!(concat!(env!("OUT_DIR"), "/error_{}.rs"));"#, idx));
+    }
+    all.push_str("\nlong_codes\n");
+    all.push_str("}\n");
+
+    fs::write(&dest, all).unwrap();
+}

src/tools/error_index_generator/main.rs

@@ -2,22 +2,20 @@
 
 extern crate env_logger;
 extern crate syntax;
-extern crate serialize as rustc_serialize;
 
 use std::collections::BTreeMap;
 use std::env;
 use std::error::Error;
-use std::fs::{self, read_dir, File};
+use std::fs::File;
 use std::io::Write;
 use std::path::Path;
 use std::path::PathBuf;
 use std::cell::RefCell;
 
 use syntax::edition::DEFAULT_EDITION;
-use syntax::diagnostics::metadata::{get_metadata_dir, ErrorMetadataMap, ErrorMetadata};
+use syntax::diagnostics::metadata::{ErrorMetadataMap, ErrorMetadata};
 
 use rustdoc::html::markdown::{Markdown, IdMap, ErrorCodes, Playground};
-use rustc_serialize::json;
 
 enum OutputFormat {
     HTML(HTMLFormatter),
@@ -80,11 +78,7 @@ impl Formatter for HTMLFormatter {
             Some(_) => "error-described",
             None => "error-undescribed",
         };
-        let use_desc = match info.use_site {
-            Some(_) => "error-used",
-            None => "error-unused",
-        };
-        write!(output, "<div class=\"{} {}\">", desc_desc, use_desc)?;
+        write!(output, "<div class=\"{}\">", desc_desc)?;
 
         // Error title (with self-link).
         write!(output,
@@ -199,25 +193,6 @@ impl Formatter for MarkdownFormatter {
     }
 }
 
-/// Loads all the metadata files from `metadata_dir` into an in-memory map.
-fn load_all_errors(metadata_dir: &Path) -> Result<ErrorMetadataMap, Box<dyn Error>> {
-    let mut all_errors = BTreeMap::new();
-
-    for entry in read_dir(metadata_dir)? {
-        let path = entry?.path();
-
-        let metadata_str = fs::read_to_string(&path)?;
-
-        let some_errors: ErrorMetadataMap = json::decode(&metadata_str)?;
-
-        for (err_code, info) in some_errors {
-            all_errors.insert(err_code, info);
-        }
-    }
-
-    Ok(all_errors)
-}
-
 /// Output an HTML page for the errors in `err_map` to `output_path`.
 fn render_error_page<T: Formatter>(err_map: &ErrorMetadataMap, output_path: &Path,
                                    formatter: T) -> Result<(), Box<dyn Error>> {
@@ -234,9 +209,16 @@ fn render_error_page<T: Formatter>(err_map: &ErrorMetadataMap, output_path: &Pat
 }
 
 fn main_with_result(format: OutputFormat, dst: &Path) -> Result<(), Box<dyn Error>> {
-    let build_arch = env::var("CFG_BUILD")?;
-    let metadata_dir = get_metadata_dir(&build_arch);
-    let err_map = load_all_errors(&metadata_dir)?;
+    let long_codes = register_all();
+    let mut err_map = BTreeMap::new();
+    for (code, desc) in long_codes {
+        err_map.insert(code.to_string(), ErrorMetadata {
+            description: desc.map(String::from),
+            // FIXME: this indicates that the error code is not used, which may not be true.
+            // We currently do not use this information.
+            use_site: None,
+        });
+    }
     match format {
         OutputFormat::Unknown(s)  => panic!("Unknown output format: {}", s),
         OutputFormat::HTML(h)     => render_error_page(&err_map, dst, h)?,
@@ -272,3 +254,5 @@ fn main() {
         panic!("{}", e.description());
     }
 }
+
+include!(concat!(env!("OUT_DIR"), "/error_codes.rs"));