rustdoc: add --print option

compiler/rustc_driver_impl/src/lib.rs

@@ -625,7 +625,7 @@ fn list_metadata(sess: &Session, metadata_loader: &dyn MetadataLoader) {
     }
 }
 
-fn print_crate_info(
+pub fn print_crate_info(
     codegen_backend: &dyn CodegenBackend,
     sess: &Session,
     parse_attrs: bool,

compiler/rustc_session/src/config.rs

@@ -33,7 +33,7 @@ use tracing::debug;
 
 pub use crate::config::cfg::{Cfg, CheckCfg, ExpectedValues};
 use crate::config::native_libs::parse_native_libs;
-pub use crate::config::print_request::{PrintKind, PrintRequest};
+pub use crate::config::print_request::{PrintKind, PrintRequest, collect_print_requests};
 use crate::errors::FileWriteFail;
 pub use crate::options::*;
 use crate::search_paths::SearchPath;
@@ -1364,16 +1364,15 @@ impl Sysroot {
     }
 }
 
+/// Get the host triple out of the build environment. This ensures that our
+/// idea of the host triple is the same as for the set of libraries we've
+/// actually built. We can't just take LLVM's host triple because they
+/// normalize all ix86 architectures to i386.
 pub fn host_tuple() -> &'static str {
-    // Get the host triple out of the build environment. This ensures that our
-    // idea of the host triple is the same as for the set of libraries we've
-    // actually built. We can't just take LLVM's host triple because they
-    // normalize all ix86 architectures to i386.
-    //
     // Instead of grabbing the host triple (for the current host), we grab (at
     // compile time) the target triple that this rustc is built with and
     // calling that (at runtime) the host triple.
-    (option_env!("CFG_COMPILER_HOST_TRIPLE")).expect("CFG_COMPILER_HOST_TRIPLE")
+    env!("CFG_COMPILER_HOST_TRIPLE")
 }
 
 fn file_path_mapping(

compiler/rustc_session/src/config/print_request.rs

@@ -21,30 +21,78 @@ pub struct PrintRequest {
 #[derive(AllVariants)]
 pub enum PrintKind {
     // tidy-alphabetical-start
+    /// All target specs.
     AllTargetSpecsJson,
+
+    /// Does the backend supports Zstd compression? (perma-unstable)
     BackendHasZstd,
+
+    /// List of supported calling conventions.
     CallingConventions,
+
+    /// List of cfg values (1st flavour).
     Cfg,
+
+    /// List of cfg values (2nd flavour).
     CheckCfg,
+
+    /// List of available code models for the current backend.
     CodeModels,
+
+    /// Name of the crate being compiled.
     CrateName,
+
     CrateRootLintLevels,
+
+    /// The current selected deployment target (Apple platforms).
     DeploymentTarget,
+
+    /// THe names of the files created by the `link` `--emit` kind.
     FileNames,
+
+    /// Target-tuple of the host compiler.
     HostTuple,
+
+    /// Linker invocations.
     LinkArgs,
+
+    /// When compiling a `staticlib` crate, print the linker flags used.
     NativeStaticLibs,
+
+    /// List of available relocation models for the current backend.
     RelocationModels,
+
+    /// List of available split debuginfos for the current target.
     SplitDebuginfo,
+
+    /// List of available stack protector strategies for the current backend.
     StackProtectorStrategies,
+
+    /// List of available crate types for the current target.
     SupportedCrateTypes,
+
+    /// Path to the sysroot.
     Sysroot,
+
+    /// List of available CPU values for the current target.
     TargetCPUs,
+
+    /// List of available target features for the current target.
     TargetFeatures,
+
+    /// Path to the target libdir.
     TargetLibdir,
+
+    /// List of supported targets.
     TargetList,
+
+    /// Current target spec.
     TargetSpecJson,
+
+    /// Target spec schema.
     TargetSpecJsonSchema,
+
+    /// List of available TLS models for the current backend.
     TlsModels,
     // tidy-alphabetical-end
 }
@@ -142,7 +190,7 @@ pub(crate) static PRINT_HELP: LazyLock<String> = LazyLock::new(|| {
     )
 });
 
-pub(crate) fn collect_print_requests(
+pub fn collect_print_requests(
     early_dcx: &EarlyDiagCtxt,
     cg: &mut CodegenOptions,
     unstable_opts: &UnstableOptions,

src/librustdoc/config.rs

@@ -9,8 +9,9 @@ use rustc_data_structures::fx::FxIndexMap;
 use rustc_errors::DiagCtxtHandle;
 use rustc_session::config::{
     self, CodegenOptions, CrateType, ErrorOutputType, Externs, Input, JsonUnusedExterns,
-    OptionsTargetModifiers, OutFileName, Sysroot, UnstableOptions, get_cmd_lint_options,
-    nightly_options, parse_crate_types_from_list, parse_externs, parse_target_triple,
+    OptionsTargetModifiers, OutFileName, PrintKind, PrintRequest, Sysroot, UnstableOptions,
+    collect_print_requests, get_cmd_lint_options, nightly_options, parse_crate_types_from_list,
+    parse_externs, parse_target_triple,
 };
 use rustc_session::lint::Level;
 use rustc_session::search_paths::SearchPath;
@@ -119,6 +120,8 @@ pub(crate) struct Options {
     pub(crate) describe_lints: bool,
     /// What level to cap lints at.
     pub(crate) lint_cap: Option<Level>,
+    /// Print requests to hand to the compiler.
+    pub(crate) prints: Vec<PrintRequest>,
 
     // Options specific to running doctests
     /// Whether we should run doctests instead of generating docs.
@@ -210,6 +213,7 @@ impl fmt::Debug for Options {
             .field("lint_opts", &self.lint_opts)
             .field("describe_lints", &self.describe_lints)
             .field("lint_cap", &self.lint_cap)
+            .field("prints", &self.prints)
             .field("should_test", &self.should_test)
             .field("test_args", &self.test_args)
             .field("test_run_directory", &self.test_run_directory)
@@ -410,7 +414,7 @@ impl Options {
         let diagnostic_width = matches.opt_get("diagnostic-width").unwrap_or_default();
 
         let mut target_modifiers = BTreeMap::<OptionsTargetModifiers, String>::new();
-        let codegen_options = CodegenOptions::build(early_dcx, matches, &mut target_modifiers);
+        let mut codegen_options = CodegenOptions::build(early_dcx, matches, &mut target_modifiers);
         let unstable_opts = UnstableOptions::build(early_dcx, matches, &mut target_modifiers);
 
         let remap_path_prefix = match parse_remap_path_prefix(matches) {
@@ -564,6 +568,41 @@ impl Options {
             }
         };
 
+        let mut prints =
+            collect_print_requests(early_dcx, &mut codegen_options, &unstable_opts, matches);
+
+        {
+            use PrintKind::*;
+            prints.retain(|req| match req.kind {
+                // Compiler
+                TargetList
+                | AllTargetSpecsJson
+                | TargetSpecJson
+                | TargetSpecJsonSchema
+                | TargetCPUs
+                | TargetFeatures
+                | DeploymentTarget
+                | SupportedCrateTypes
+
+                // Codegen
+                | CallingConventions
+                | CodeModels
+                | SplitDebuginfo
+                | StackProtectorStrategies
+                | RelocationModels
+                | TlsModels
+                | BackendHasZstd
+
+                // Linker
+                | FileNames
+                | LinkArgs
+                | NativeStaticLibs
+                | TargetLibdir => false,
+
+                Cfg | CheckCfg | CrateName | CrateRootLintLevels | HostTuple | Sysroot => true,
+            });
+        }
+
         let externs = parse_externs(early_dcx, matches, &unstable_opts);
         let extern_html_root_urls = match parse_extern_html_roots(matches) {
             Ok(ex) => ex,
@@ -853,6 +892,7 @@ impl Options {
             lint_opts,
             describe_lints,
             lint_cap,
+            prints,
             should_test,
             test_args,
             show_coverage,

src/librustdoc/core.rs

@@ -214,6 +214,7 @@ pub(crate) fn create_config(
         lint_opts,
         describe_lints,
         lint_cap,
+        prints,
         scrape_examples_options,
         remap_path_prefix,
         target_modifiers,
@@ -269,6 +270,7 @@ pub(crate) fn create_config(
         diagnostic_width,
         edition,
         describe_lints,
+        prints,
         crate_name,
         test,
         remap_path_prefix,

src/librustdoc/lib.rs

@@ -542,6 +542,14 @@ fn opts() -> Vec<RustcOptGroup> {
             "Comma separated list of types of output for rustdoc to emit",
             "[toolchain-shared-resources,invocation-specific,dep-info]",
         ),
+        opt(
+            Unstable,
+            Multi,
+            "",
+            "print",
+            "Rustdoc information to print on stdout (or to a file)",
+            "<INFO>[=<FILE>]",
+        ),
         opt(Unstable, FlagMulti, "", "no-run", "Compile doctests without running them", ""),
         opt(
             Unstable,
@@ -885,6 +893,12 @@ fn main_args(early_dcx: &mut EarlyDiagCtxt, at_args: &[String]) {
             return;
         }
 
+        if rustc_driver::print_crate_info(&*compiler.codegen_backend, sess, true)
+            == rustc_driver::Compilation::Stop
+        {
+            return;
+        }
+
         let krate = rustc_interface::passes::parse(sess);
         rustc_interface::create_and_enter_global_ctxt(compiler, krate, |tcx| {
             if sess.dcx().has_errors().is_some() {

tests/run-make/rustdoc-default-output/output-default.stdout

@@ -153,6 +153,8 @@ Options:
         --emit [toolchain-shared-resources,invocation-specific,dep-info]
                         Comma separated list of types of output for rustdoc to
                         emit
+        --print <INFO>[=<FILE>]
+                        Rustdoc information to print on stdout (or to a file)
         --no-run        Compile doctests without running them
         --merge-doctests yes|no|auto
                         Force all doctests to be compiled as a single binary,