Rollup merge of #138552 - jieyouxu:print-request-cleanups, r=Urgau

Misc print request handling cleanups + a centralized test for print request stability gating

I was working on implementing `--print=supported-crate-types`, then I noticed some things that were mildly annoying me, so I pulled out these changes. In this PR:

- First commit adds a centralized test `tests/ui/print/stability.rs` that is responsible for exercising stability gating of the print requests.
    - AFAICT we didn't have any test that systematically checks this.
    - I coalesced `tests/ui/feature-gates/feature-gate-print-check-cfg.rs` (for `--print=check-cfg`) into this test too, since `--print=check-cfg` is only `-Z unstable-options`-gated like other unstable print requests, and is not additionally feature-gated. cc ``@Urgau`` in case you have any concerns.
- Second commit alphabetically sorts the `PrintKind` enum for consistency because the `PRINT_KINDS` list (using the enum) is *already* alphabetically sorted.
- Third commit pulls out two helpers:
    1. A helper `check_print_request_stability` for checking stability of print requests and the diagnostics for using unstable print requests without `-Z unstable-options`, to avoid repeating the same logic over and over.
    2. A helper `emit_unknown_print_request_help` for the unknown print request diagnostics to make print request collection control flow more obvious.
- Fourth commit renames `PrintKind::{TargetSpec,AllTargetSpecs}` to `PrintKind::{TargetSpecJson,AllTargetSpecsJson}` to better reflect their actual print names, `--print={target-spec-json,all-target-specs-json}`.

r? ``@nnethercote`` (or compiler/reroll)

2 files changed, 56 insertions, 62 deletions

diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index ed5662da16d..2d636da4a12 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -649,10 +649,10 @@ fn print_crate_info(
             HostTuple => println_info!("{}", rustc_session::config::host_tuple()),
             Sysroot => println_info!("{}", sess.sysroot.display()),
             TargetLibdir => println_info!("{}", sess.target_tlib_path.dir.display()),
-            TargetSpec => {
+            TargetSpecJson => {
                 println_info!("{}", serde_json::to_string_pretty(&sess.target.to_json()).unwrap());
             }
-            AllTargetSpecs => {
+            AllTargetSpecsJson => {
                 let mut targets = BTreeMap::new();
                 for name in rustc_target::spec::TARGETS {
                     let triple = TargetTuple::from_tuple(name);
diff --git a/compiler/rustc_session/src/config.rs b/compiler/rustc_session/src/config.rs
index 34755249b60..701d06e4fd4 100644
--- a/compiler/rustc_session/src/config.rs
+++ b/compiler/rustc_session/src/config.rs
@@ -44,7 +44,7 @@ pub mod sigpipe;
 
 pub const PRINT_KINDS: &[(&str, PrintKind)] = &[
     // tidy-alphabetical-start
-    ("all-target-specs-json", PrintKind::AllTargetSpecs),
+    ("all-target-specs-json", PrintKind::AllTargetSpecsJson),
     ("calling-conventions", PrintKind::CallingConventions),
     ("cfg", PrintKind::Cfg),
     ("check-cfg", PrintKind::CheckCfg),
@@ -63,7 +63,7 @@ pub const PRINT_KINDS: &[(&str, PrintKind)] = &[
     ("target-features", PrintKind::TargetFeatures),
     ("target-libdir", PrintKind::TargetLibdir),
     ("target-list", PrintKind::TargetList),
-    ("target-spec-json", PrintKind::TargetSpec),
+    ("target-spec-json", PrintKind::TargetSpecJson),
     ("tls-models", PrintKind::TlsModels),
     // tidy-alphabetical-end
 ];
@@ -873,27 +873,29 @@ pub struct PrintRequest {
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub enum PrintKind {
+    // tidy-alphabetical-start
+    AllTargetSpecsJson,
+    CallingConventions,
+    Cfg,
+    CheckCfg,
+    CodeModels,
+    CrateName,
+    DeploymentTarget,
     FileNames,
     HostTuple,
+    LinkArgs,
+    NativeStaticLibs,
+    RelocationModels,
+    SplitDebuginfo,
+    StackProtectorStrategies,
     Sysroot,
-    TargetLibdir,
-    CrateName,
-    Cfg,
-    CheckCfg,
-    CallingConventions,
-    TargetList,
     TargetCPUs,
     TargetFeatures,
-    RelocationModels,
-    CodeModels,
+    TargetLibdir,
+    TargetList,
+    TargetSpecJson,
     TlsModels,
-    TargetSpec,
-    AllTargetSpecs,
-    NativeStaticLibs,
-    StackProtectorStrategies,
-    LinkArgs,
-    SplitDebuginfo,
-    DeploymentTarget,
+    // tidy-alphabetical-end
 }
 
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, Default)]
@@ -2030,49 +2032,13 @@ fn collect_print_requests(
     prints.extend(matches.opt_strs("print").into_iter().map(|req| {
         let (req, out) = split_out_file_name(&req);
 
-        let kind = match PRINT_KINDS.iter().find(|&&(name, _)| name == req) {
-            Some((_, PrintKind::TargetSpec)) => {
-                if unstable_opts.unstable_options {
-                    PrintKind::TargetSpec
-                } else {
-                    early_dcx.early_fatal(
-                        "the `-Z unstable-options` flag must also be passed to \
-                         enable the target-spec-json print option",
-                    );
-                }
-            }
-            Some((_, PrintKind::AllTargetSpecs)) => {
-                if unstable_opts.unstable_options {
-                    PrintKind::AllTargetSpecs
-                } else {
-                    early_dcx.early_fatal(
-                        "the `-Z unstable-options` flag must also be passed to \
-                         enable the all-target-specs-json print option",
-                    );
-                }
-            }
-            Some((_, PrintKind::CheckCfg)) => {
-                if unstable_opts.unstable_options {
-                    PrintKind::CheckCfg
-                } else {
-                    early_dcx.early_fatal(
-                        "the `-Z unstable-options` flag must also be passed to \
-                         enable the check-cfg print option",
-                    );
-                }
-            }
-            Some(&(_, print_kind)) => print_kind,
-            None => {
-                let prints =
-                    PRINT_KINDS.iter().map(|(name, _)| format!("`{name}`")).collect::<Vec<_>>();
-                let prints = prints.join(", ");
-
-                let mut diag =
-                    early_dcx.early_struct_fatal(format!("unknown print request: `{req}`"));
-                #[allow(rustc::diagnostic_outside_of_impl)]
-                diag.help(format!("valid print requests are: {prints}"));
-                diag.emit()
-            }
+        let kind = if let Some((print_name, print_kind)) =
+            PRINT_KINDS.iter().find(|&&(name, _)| name == req)
+        {
+            check_print_request_stability(early_dcx, unstable_opts, (print_name, *print_kind));
+            *print_kind
+        } else {
+            emit_unknown_print_request_help(early_dcx, req)
         };
 
         let out = out.unwrap_or(OutFileName::Stdout);
@@ -2091,6 +2057,34 @@ fn collect_print_requests(
     prints
 }
 
+fn check_print_request_stability(
+    early_dcx: &EarlyDiagCtxt,
+    unstable_opts: &UnstableOptions,
+    (print_name, print_kind): (&str, PrintKind),
+) {
+    match print_kind {
+        PrintKind::AllTargetSpecsJson | PrintKind::CheckCfg | PrintKind::TargetSpecJson
+            if !unstable_opts.unstable_options =>
+        {
+            early_dcx.early_fatal(format!(
+                "the `-Z unstable-options` flag must also be passed to enable the `{print_name}` \
+                print option"
+            ));
+        }
+        _ => {}
+    }
+}
+
+fn emit_unknown_print_request_help(early_dcx: &EarlyDiagCtxt, req: &str) -> ! {
+    let prints = PRINT_KINDS.iter().map(|(name, _)| format!("`{name}`")).collect::<Vec<_>>();
+    let prints = prints.join(", ");
+
+    let mut diag = early_dcx.early_struct_fatal(format!("unknown print request: `{req}`"));
+    #[allow(rustc::diagnostic_outside_of_impl)]
+    diag.help(format!("valid print requests are: {prints}"));
+    diag.emit()
+}
+
 pub fn parse_target_triple(early_dcx: &EarlyDiagCtxt, matches: &getopts::Matches) -> TargetTuple {
     match matches.opt_str("target") {
         Some(target) if target.ends_with(".json") => {