From 7e95a22e1f6c3aae57da66c38c0b1bc0f1207893 Mon Sep 17 00:00:00 2001
From: yukang <moorekang@gmail.com>
Date: Thu, 26 Mar 2026 22:02:11 +0800
Subject: [PATCH] rustdoc rejects html emits with json output

---
 src/librustdoc/config.rs                             | 12 ++++++++++++
 ...tput-format-json-emit-html.html_non_static.stderr |  2 ++
 .../output-format-json-emit-html.html_static.stderr  |  2 ++
 tests/rustdoc-ui/output-format-json-emit-html.rs     |  8 ++++++++
 .../show-coverage-json-emit-html-non-static.rs       |  5 +++++
 .../show-coverage-json-emit-html-non-static.stderr   |  2 ++
 6 files changed, 31 insertions(+)
 create mode 100644 tests/rustdoc-ui/output-format-json-emit-html.html_non_static.stderr
 create mode 100644 tests/rustdoc-ui/output-format-json-emit-html.html_static.stderr
 create mode 100644 tests/rustdoc-ui/output-format-json-emit-html.rs
 create mode 100644 tests/rustdoc-ui/show-coverage-json-emit-html-non-static.rs
 create mode 100644 tests/rustdoc-ui/show-coverage-json-emit-html-non-static.stderr

diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index d721034c2d71..3caff6edd504 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -522,6 +522,18 @@ fn println_condition(condition: Condition) {
             }
         }
 
+        if output_format == OutputFormat::Json {
+            if let Some(emit_flag) = emit.iter().find_map(|emit| match emit {
+                EmitType::HtmlStaticFiles => Some("html-static-files"),
+                EmitType::HtmlNonStaticFiles => Some("html-non-static-files"),
+                EmitType::DepInfo(_) => None,
+            }) {
+                dcx.fatal(format!(
+                    "the `--emit={emit_flag}` flag is not supported with `--output-format=json`",
+                ));
+            }
+        }
+
         let to_check = matches.opt_strs("check-theme");
         if !to_check.is_empty() {
             let mut content =
diff --git a/tests/rustdoc-ui/output-format-json-emit-html.html_non_static.stderr b/tests/rustdoc-ui/output-format-json-emit-html.html_non_static.stderr
new file mode 100644
index 000000000000..8d8e8c6d1228
--- /dev/null
+++ b/tests/rustdoc-ui/output-format-json-emit-html.html_non_static.stderr
@@ -0,0 +1,2 @@
+error: the `--emit=html-non-static-files` flag is not supported with `--output-format=json`
+
diff --git a/tests/rustdoc-ui/output-format-json-emit-html.html_static.stderr b/tests/rustdoc-ui/output-format-json-emit-html.html_static.stderr
new file mode 100644
index 000000000000..bc1ddc1b155d
--- /dev/null
+++ b/tests/rustdoc-ui/output-format-json-emit-html.html_static.stderr
@@ -0,0 +1,2 @@
+error: the `--emit=html-static-files` flag is not supported with `--output-format=json`
+
diff --git a/tests/rustdoc-ui/output-format-json-emit-html.rs b/tests/rustdoc-ui/output-format-json-emit-html.rs
new file mode 100644
index 000000000000..7a99cbd91ba6
--- /dev/null
+++ b/tests/rustdoc-ui/output-format-json-emit-html.rs
@@ -0,0 +1,8 @@
+//@ revisions: html_static html_non_static
+//@ check-fail
+//@[html_static] compile-flags: -Z unstable-options --output-format=json --emit=html-static-files
+//@[html_non_static] compile-flags: -Z unstable-options --output-format=json --emit=html-non-static-files
+//[html_static]~? ERROR the `--emit=html-static-files` flag is not supported with `--output-format=json`
+//[html_non_static]~? ERROR the `--emit=html-non-static-files` flag is not supported with `--output-format=json`
+
+pub struct Foo;
diff --git a/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.rs b/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.rs
new file mode 100644
index 000000000000..b0f67a3b4195
--- /dev/null
+++ b/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.rs
@@ -0,0 +1,5 @@
+//@ compile-flags: -Z unstable-options --show-coverage --output-format=json --emit=html-non-static-files
+//@ check-fail
+//~? ERROR the `--emit=html-non-static-files` flag is not supported with `--output-format=json`
+
+pub struct Foo;
diff --git a/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.stderr b/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.stderr
new file mode 100644
index 000000000000..8d8e8c6d1228
--- /dev/null
+++ b/tests/rustdoc-ui/show-coverage-json-emit-html-non-static.stderr
@@ -0,0 +1,2 @@
+error: the `--emit=html-non-static-files` flag is not supported with `--output-format=json`
+