Auto merge of #79539 - aDotInTheVoid:json-mvp, r=jyn514

Rustdoc: JSON backend experimental impl, with new tests.

Based on #75114 by `@P1n3appl3`

The first commit is all of #75114, but squased to 1 commit, as that was much easier to rebase onto master.

The git history is a mess, but I think I'll edit it after review, so it's obvious whats new.

## Still to do

- [ ] Update docs.
- [ ] Add bless option to tests.
- [ ] Add test option for multiple files in same crate.
- [ ] Decide if the tests should check for json to be equal or subset.
- [ ] Go through the rest of the review for the original pr. (This is open because the test system is done(ish), but stuff like [not using a hashmap](https://github.com/rust-lang/rust/pull/75114#discussion_r519474420) and [using `CRATE_DEF_INDEX` ](https://github.com/rust-lang/rust/pull/75114#discussion_r519470764) hasn't)

I'm also sure how many of these we need to do before landing on nightly, as it would be nice to get this in tree, so it isn't effected by churn like #79125, #79041, #79061

r? `@jyn514`

3 files changed, 57 insertions, 5 deletions

diff --git a/src/tools/compiletest/src/common.rs b/src/tools/compiletest/src/common.rs
index 24ef98cd784..eba02333c8c 100644
--- a/src/tools/compiletest/src/common.rs
+++ b/src/tools/compiletest/src/common.rs
@@ -17,6 +17,7 @@ pub enum Mode {
     DebugInfo,
     Codegen,
     Rustdoc,
+    RustdocJson,
     CodegenUnits,
     Incremental,
     RunMake,
@@ -48,6 +49,7 @@ impl FromStr for Mode {
             "debuginfo" => Ok(DebugInfo),
             "codegen" => Ok(Codegen),
             "rustdoc" => Ok(Rustdoc),
+            "rustdoc-json" => Ok(RustdocJson),
             "codegen-units" => Ok(CodegenUnits),
             "incremental" => Ok(Incremental),
             "run-make" => Ok(RunMake),
@@ -70,6 +72,7 @@ impl fmt::Display for Mode {
             DebugInfo => "debuginfo",
             Codegen => "codegen",
             Rustdoc => "rustdoc",
+            RustdocJson => "rustdoc-json",
             CodegenUnits => "codegen-units",
             Incremental => "incremental",
             RunMake => "run-make",
diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index 32347db5dbb..0541548aefd 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -68,7 +68,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
             "mode",
             "which sort of compile tests to run",
             "compile-fail | run-fail | run-pass-valgrind | pretty | debug-info | codegen | rustdoc \
-             codegen-units | incremental | run-make | ui | js-doc-test | mir-opt | assembly",
+            | rustdoc-json | codegen-units | incremental | run-make | ui | js-doc-test | mir-opt | assembly",
         )
         .reqopt(
             "",
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 1b9f0089dce..e9089b4b15b 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2,7 +2,7 @@
 
 use crate::common::{expected_output_path, UI_EXTENSIONS, UI_FIXED, UI_STDERR, UI_STDOUT};
 use crate::common::{output_base_dir, output_base_name, output_testname_unique};
-use crate::common::{Assembly, Incremental, JsDocTest, MirOpt, RunMake, Ui};
+use crate::common::{Assembly, Incremental, JsDocTest, MirOpt, RunMake, RustdocJson, Ui};
 use crate::common::{Codegen, CodegenUnits, DebugInfo, Debugger, Rustdoc};
 use crate::common::{CompareMode, FailMode, PassMode};
 use crate::common::{CompileFail, Pretty, RunFail, RunPassValgrind};
@@ -342,6 +342,7 @@ impl<'test> TestCx<'test> {
             DebugInfo => self.run_debuginfo_test(),
             Codegen => self.run_codegen_test(),
             Rustdoc => self.run_rustdoc_test(),
+            RustdocJson => self.run_rustdoc_json_test(),
             CodegenUnits => self.run_codegen_units_test(),
             Incremental => self.run_incremental_test(),
             RunMake => self.run_rmake_test(),
@@ -1600,6 +1601,10 @@ impl<'test> TestCx<'test> {
             .arg(&self.testpaths.file)
             .args(&self.props.compile_flags);
 
+        if self.config.mode == RustdocJson {
+            rustdoc.arg("--output-format").arg("json");
+        }
+
         if let Some(ref linker) = self.config.linker {
             rustdoc.arg(format!("-Clinker={}", linker));
         }
@@ -1887,7 +1892,9 @@ impl<'test> TestCx<'test> {
     }
 
     fn is_rustdoc(&self) -> bool {
-        self.config.src_base.ends_with("rustdoc-ui") || self.config.src_base.ends_with("rustdoc-js")
+        self.config.src_base.ends_with("rustdoc-ui")
+            || self.config.src_base.ends_with("rustdoc-js")
+            || self.config.src_base.ends_with("rustdoc-json")
     }
 
     fn make_compile_args(
@@ -1968,8 +1975,8 @@ impl<'test> TestCx<'test> {
 
                 rustc.arg(dir_opt);
             }
-            RunFail | RunPassValgrind | Pretty | DebugInfo | Codegen | Rustdoc | RunMake
-            | CodegenUnits | JsDocTest | Assembly => {
+            RunFail | RunPassValgrind | Pretty | DebugInfo | Codegen | Rustdoc | RustdocJson
+            | RunMake | CodegenUnits | JsDocTest | Assembly => {
                 // do not use JSON output
             }
         }
@@ -2466,6 +2473,48 @@ impl<'test> TestCx<'test> {
         eprintln!("{}", String::from_utf8_lossy(&output.stderr));
     }
 
+    fn run_rustdoc_json_test(&self) {
+        //FIXME: Add bless option.
+
+        assert!(self.revision.is_none(), "revisions not relevant here");
+
+        let out_dir = self.output_base_dir();
+        let _ = fs::remove_dir_all(&out_dir);
+        create_dir_all(&out_dir).unwrap();
+
+        let proc_res = self.document(&out_dir);
+        if !proc_res.status.success() {
+            self.fatal_proc_rec("rustdoc failed!", &proc_res);
+        }
+
+        let root = self.config.find_rust_src_root().unwrap();
+        let mut json_out = out_dir.join(self.testpaths.file.file_stem().unwrap());
+        json_out.set_extension("json");
+        let res = self.cmd2procres(
+            Command::new(&self.config.docck_python)
+                .arg(root.join("src/test/rustdoc-json/check_missing_items.py"))
+                .arg(&json_out),
+        );
+
+        if !res.status.success() {
+            self.fatal_proc_rec("check_missing_items failed!", &res);
+        }
+
+        let mut expected = self.testpaths.file.clone();
+        expected.set_extension("expected");
+        let res = self.cmd2procres(
+            Command::new(&self.config.docck_python)
+                .arg(root.join("src/test/rustdoc-json/compare.py"))
+                .arg(&expected)
+                .arg(&json_out)
+                .arg(&expected.parent().unwrap()),
+        );
+
+        if !res.status.success() {
+            self.fatal_proc_rec("compare failed!", &res);
+        }
+    }
+
     fn get_lines<P: AsRef<Path>>(
         &self,
         path: &P,