Add a bootstrap setting and compiletest flag for --new-output-capture

Author: Zalathar

bootstrap.example.toml

@@ -473,6 +473,10 @@
 # when the stage 0 compiler is actually built from in-tree sources.
 #build.compiletest-allow-stage0 = false
 
+# Whether to enable or disable the new output-capture implementation in compiletest.
+# This setting will be removed when the "old" output-capture implementation is removed.
+#build.compiletest-new-output-capture = false
+
 # Whether to use the precompiled stage0 libtest with compiletest.
 #build.compiletest-use-stage0-libtest = true
 

src/bootstrap/src/core/build_steps/test.rs

@@ -1955,6 +1955,10 @@ HELP: You can add it into `bootstrap.toml` in `rust.codegen-backends = [{name:?}
         if builder.config.cmd.no_capture() {
             cmd.arg("--no-capture");
         }
+        cmd.args([
+            "--new-output-capture",
+            if builder.build.config.compiletest_new_output_capture { "on" } else { "off" },
+        ]);
 
         let compare_mode =
             builder.config.cmd.compare_mode().or_else(|| {

src/bootstrap/src/core/config/config.rs

@@ -307,6 +307,9 @@ pub struct Config {
     /// sources.
     pub compiletest_allow_stage0: bool,
 
+    /// Whether to enable or disable the new output-capture implementation in compiletest.
+    pub compiletest_new_output_capture: bool,
+
     /// Whether to use the precompiled stage0 libtest with compiletest.
     pub compiletest_use_stage0_libtest: bool,
 
@@ -479,6 +482,7 @@ impl Config {
             optimized_compiler_builtins: build_optimized_compiler_builtins,
             jobs: build_jobs,
             compiletest_diff_tool: build_compiletest_diff_tool,
+            compiletest_new_output_capture: build_compiletest_new_output_capture,
             compiletest_use_stage0_libtest: build_compiletest_use_stage0_libtest,
             tidy_extra_checks: build_tidy_extra_checks,
             ccache: build_ccache,
@@ -1152,6 +1156,7 @@ impl Config {
             compiler_docs: build_compiler_docs.unwrap_or(false),
             compiletest_allow_stage0: build_compiletest_allow_stage0.unwrap_or(false),
             compiletest_diff_tool: build_compiletest_diff_tool,
+            compiletest_new_output_capture: build_compiletest_new_output_capture.unwrap_or(false),
             compiletest_use_stage0_libtest: build_compiletest_use_stage0_libtest.unwrap_or(true),
             config: toml_path,
             configure_args: build_configure_args.unwrap_or_default(),

src/bootstrap/src/core/config/toml/build.rs

@@ -69,6 +69,7 @@ define_config! {
         jobs: Option<u32> = "jobs",
         compiletest_diff_tool: Option<String> = "compiletest-diff-tool",
         compiletest_allow_stage0: Option<bool> = "compiletest-allow-stage0",
+        compiletest_new_output_capture: Option<bool> = "compiletest-new-output-capture",
         compiletest_use_stage0_libtest: Option<bool> = "compiletest-use-stage0-libtest",
         tidy_extra_checks: Option<String> = "tidy-extra-checks",
         ccache: Option<StringOrBool> = "ccache",

src/tools/compiletest/src/common.rs

@@ -667,6 +667,10 @@ pub struct Config {
     /// to avoid `!nocapture` double-negatives.
     pub nocapture: bool,
 
+    /// True if the experimental new output-capture implementation should be
+    /// used, avoiding the need for `#![feature(internal_output_capture)]`.
+    pub new_output_capture: bool,
+
     /// Needed both to construct [`build_helper::git::GitConfig`].
     pub nightly_branch: String,
     pub git_merge_commit_email: String,
@@ -784,6 +788,7 @@ impl Config {
             builtin_cfg_names: Default::default(),
             supported_crate_types: Default::default(),
             nocapture: Default::default(),
+            new_output_capture: Default::default(),
             nightly_branch: Default::default(),
             git_merge_commit_email: Default::default(),
             profiler_runtime: Default::default(),

src/tools/compiletest/src/lib.rs

@@ -178,6 +178,15 @@ pub fn parse_config(args: Vec<String>) -> Config {
         // FIXME: Temporarily retained so we can point users to `--no-capture`
         .optflag("", "nocapture", "")
         .optflag("", "no-capture", "don't capture stdout/stderr of tests")
+        // New-output-capture needs to be `optmulti` so that the value passed
+        // by bootstrap can be overridden explicitly if desired
+        // (e.g. `x test ui -- --new-output-capture=on`).
+        .optmulti(
+            "N",
+            "new-output-capture",
+            "enables or disables the new output-capture implementation",
+            "off|on",
+        )
         .optflag("", "profiler-runtime", "is the profiler runtime enabled for this target")
         .optflag("h", "help", "show this message")
         .reqopt("", "channel", "current Rust channel", "CHANNEL")
@@ -462,6 +471,16 @@ pub fn parse_config(args: Vec<String>) -> Config {
         supported_crate_types: OnceLock::new(),
 
         nocapture: matches.opt_present("no-capture"),
+        new_output_capture: {
+            // Ignore all but the last occurrence, so that an explicit override
+            // (e.g. `x test ui -- --new-output-capture=on`) takes precedence
+            // over whatever was passed by bootstrap.
+            let values = matches.opt_strs("new-output-capture");
+            // New-output-capture currently defaults to off.
+            let value = values.last().map(String::as_str).unwrap_or("off");
+            parse_bool_option(value)
+                .unwrap_or_else(|| panic!("unknown `--new-output-capture` value `{value}` given"))
+        },
 
         nightly_branch: matches.opt_str("nightly-branch").unwrap(),
         git_merge_commit_email: matches.opt_str("git-merge-commit-email").unwrap(),
@@ -477,6 +496,14 @@ pub fn parse_config(args: Vec<String>) -> Config {
     }
 }
 
+fn parse_bool_option(value: &str) -> Option<bool> {
+    match value {
+        "off" | "no" | "n" | "false" => Some(false),
+        "on" | "yes" | "y" | "true" => Some(true),
+        _ => None,
+    }
+}
+
 pub fn opt_str(maybestr: &Option<String>) -> &str {
     match *maybestr {
         None => "(none)",