Rollup merge of rust-lang#50541 - QuietMisdreavus:rustdoc-errors, r=GuillaumeGomez

rustdoc: replace most (e)println! statements with structured warnings/errors

Turns out, the rustc diagnostic handler doesn't need a whole lot of setup that we weren't already doing. For errors that occur outside a "dealing with source code" context, we can just use the format/color config we were already parsing and make up a `Handler` that we can emit structured warnings/errors from. So i did that. This will make it way easier to test things with `rustdoc-ui` tests, since those require the JSON error output. (In fact, this PR is a yak shave for a different one where i was trying to do just that. `>_>`)

Author: kennytm

Diff for: src/librustdoc/core.rs

@@ -117,6 +117,57 @@ impl DocAccessLevels for AccessLevels<DefId> {
     }
 }
 
+/// Creates a new diagnostic `Handler` that can be used to emit warnings and errors.
+///
+/// If the given `error_format` is `ErrorOutputType::Json` and no `CodeMap` is given, a new one
+/// will be created for the handler.
+pub fn new_handler(error_format: ErrorOutputType, codemap: Option<Lrc<codemap::CodeMap>>)
+    -> errors::Handler
+{
+    // rustdoc doesn't override (or allow to override) anything from this that is relevant here, so
+    // stick to the defaults
+    let sessopts = config::basic_options();
+    let emitter: Box<dyn Emitter + sync::Send> = match error_format {
+        ErrorOutputType::HumanReadable(color_config) => Box::new(
+            EmitterWriter::stderr(
+                color_config,
+                codemap.map(|cm| cm as _),
+                false,
+                sessopts.debugging_opts.teach,
+            ).ui_testing(sessopts.debugging_opts.ui_testing)
+        ),
+        ErrorOutputType::Json(pretty) => {
+            let codemap = codemap.unwrap_or_else(
+                || Lrc::new(codemap::CodeMap::new(sessopts.file_path_mapping())));
+            Box::new(
+                JsonEmitter::stderr(
+                    None,
+                    codemap,
+                    pretty,
+                    sessopts.debugging_opts.suggestion_applicability,
+                ).ui_testing(sessopts.debugging_opts.ui_testing)
+            )
+        },
+        ErrorOutputType::Short(color_config) => Box::new(
+            EmitterWriter::stderr(
+                color_config,
+                codemap.map(|cm| cm as _),
+                true,
+                false)
+        ),
+    };
+
+    errors::Handler::with_emitter_and_flags(
+        emitter,
+        errors::HandlerFlags {
+            can_emit_warnings: true,
+            treat_err_as_bug: false,
+            external_macro_backtrace: false,
+            ..Default::default()
+        },
+    )
+}
+
 pub fn run_core(search_paths: SearchPaths,
                 cfgs: Vec<String>,
                 externs: config::Externs,
@@ -159,41 +210,11 @@ pub fn run_core(search_paths: SearchPaths,
         },
         error_format,
         edition,
-        ..config::basic_options().clone()
+        ..config::basic_options()
     };
     driver::spawn_thread_pool(sessopts, move |sessopts| {
         let codemap = Lrc::new(codemap::CodeMap::new(sessopts.file_path_mapping()));
-        let emitter: Box<dyn Emitter + sync::Send> = match error_format {
-            ErrorOutputType::HumanReadable(color_config) => Box::new(
-                EmitterWriter::stderr(
-                    color_config,
-                    Some(codemap.clone()),
-                    false,
-                    sessopts.debugging_opts.teach,
-                ).ui_testing(sessopts.debugging_opts.ui_testing)
-            ),
-            ErrorOutputType::Json(pretty) => Box::new(
-                JsonEmitter::stderr(
-                    None,
-                    codemap.clone(),
-                    pretty,
-                    sessopts.debugging_opts.suggestion_applicability,
-                ).ui_testing(sessopts.debugging_opts.ui_testing)
-            ),
-            ErrorOutputType::Short(color_config) => Box::new(
-                EmitterWriter::stderr(color_config, Some(codemap.clone()), true, false)
-            ),
-        };
-
-        let diagnostic_handler = errors::Handler::with_emitter_and_flags(
-            emitter,
-            errors::HandlerFlags {
-                can_emit_warnings: true,
-                treat_err_as_bug: false,
-                external_macro_backtrace: false,
-                ..Default::default()
-            },
-        );
+        let diagnostic_handler = new_handler(error_format, Some(codemap.clone()));
 
         let mut sess = session::build_session_(
             sessopts, cpath, diagnostic_handler, codemap,

Diff for: src/librustdoc/externalfiles.rs

@@ -11,6 +11,7 @@
 use std::fs;
 use std::path::Path;
 use std::str;
+use errors;
 use html::markdown::Markdown;
 
 #[derive(Clone)]
@@ -28,23 +29,23 @@ pub struct ExternalHtml {
 
 impl ExternalHtml {
     pub fn load(in_header: &[String], before_content: &[String], after_content: &[String],
-                md_before_content: &[String], md_after_content: &[String])
+                md_before_content: &[String], md_after_content: &[String], diag: &errors::Handler)
             -> Option<ExternalHtml> {
-        load_external_files(in_header)
+        load_external_files(in_header, diag)
             .and_then(|ih|
-                load_external_files(before_content)
+                load_external_files(before_content, diag)
                     .map(|bc| (ih, bc))
             )
             .and_then(|(ih, bc)|
-                load_external_files(md_before_content)
+                load_external_files(md_before_content, diag)
                     .map(|m_bc| (ih, format!("{}{}", bc, Markdown(&m_bc, &[]))))
             )
             .and_then(|(ih, bc)|
-                load_external_files(after_content)
+                load_external_files(after_content, diag)
                     .map(|ac| (ih, bc, ac))
             )
             .and_then(|(ih, bc, ac)|
-                load_external_files(md_after_content)
+                load_external_files(md_after_content, diag)
                     .map(|m_ac| (ih, bc, format!("{}{}", ac, Markdown(&m_ac, &[]))))
             )
             .map(|(ih, bc, ac)|
@@ -62,28 +63,30 @@ pub enum LoadStringError {
     BadUtf8,
 }
 
-pub fn load_string<P: AsRef<Path>>(file_path: P) -> Result<String, LoadStringError> {
+pub fn load_string<P: AsRef<Path>>(file_path: P, diag: &errors::Handler)
+    -> Result<String, LoadStringError>
+{
     let file_path = file_path.as_ref();
     let contents = match fs::read(file_path) {
         Ok(bytes) => bytes,
         Err(e) => {
-            eprintln!("error reading `{}`: {}", file_path.display(), e);
+            diag.struct_err(&format!("error reading `{}`: {}", file_path.display(), e)).emit();
             return Err(LoadStringError::ReadFail);
         }
     };
     match str::from_utf8(&contents) {
         Ok(s) => Ok(s.to_string()),
         Err(_) => {
-            eprintln!("error reading `{}`: not UTF-8", file_path.display());
+            diag.struct_err(&format!("error reading `{}`: not UTF-8", file_path.display())).emit();
             Err(LoadStringError::BadUtf8)
         }
     }
 }
 
-fn load_external_files(names: &[String]) -> Option<String> {
+fn load_external_files(names: &[String], diag: &errors::Handler) -> Option<String> {
     let mut out = String::new();
     for name in names {
-        let s = match load_string(name) {
+        let s = match load_string(name, diag) {
             Ok(s) => s,
             Err(_) => return None,
         };