Stabilize rustdoc --test-run-directory

Author: Swatinem

src/doc/rustdoc/src/command-line-arguments.md

@@ -179,7 +179,7 @@ $ rustdoc src/lib.rs --test
 This flag will run your code examples as tests. For more, see [the chapter
 on documentation tests](write-documentation/documentation-tests.md).
 
-See also `--test-args`.
+See also `--test-args` and `--test-run-directory`.
 
 ## `--test-args`: pass options to test runner
 
@@ -194,6 +194,19 @@ For more, see [the chapter on documentation tests](write-documentation/documenta
 
 See also `--test`.
 
+## `--test-run-directory`: run code examples in a specific directory
+
+Using this flag looks like this:
+
+```bash
+$ rustdoc src/lib.rs --test --test-run-directory=/path/to/working/directory
+```
+
+This flag will run your code examples in the specified working directory.
+For more, see [the chapter on documentation tests](write-documentation/documentation-tests.md).
+
+See also `--test`.
+
 ## `--target`: generate documentation for the specified target triple
 
 Using this flag looks like this:

src/doc/rustdoc/src/write-documentation/documentation-tests.md

@@ -443,3 +443,15 @@ pub struct ReadmeDoctests;
 
 This will include your README as documentation on the hidden struct `ReadmeDoctests`, which will
 then be tested alongside the rest of your doctests.
+
+## Controlling the compilation and run directories
+
+By default, `rustdoc --test` will compile and run documentation test examples
+from the same working directory.
+The compilation directory is being used for compiler diagnostics, the `file!()` macro and
+the output of `rustdoc` test runner itself, whereas the run directory has an influence on file-system
+operations within documentation test examples, such as `std::fs::read_to_string`.
+
+The `--test-run-directory` flag allows controlling the run directory separately from the compilation directory.
+This is particularly useful in workspaces, where compiler invocations and thus diagnostics should be
+relative to the workspace directory, but documentation test examples should run relative to the crate directory.

src/librustdoc/lib.rs

@@ -284,7 +284,7 @@ fn opts() -> Vec<RustcOptGroup> {
         stable("test-args", |o| {
             o.optmulti("", "test-args", "arguments to pass to the test runner", "ARGS")
         }),
-        unstable("test-run-directory", |o| {
+        stable("test-run-directory", |o| {
             o.optopt(
                 "",
                 "test-run-directory",

tests/rustdoc-ui/run-directory.rs

@@ -2,8 +2,8 @@
 
 // revisions: correct incorrect
 // check-pass
-// [correct]compile-flags:--test --test-run-directory={{src-base}} -Zunstable-options
-// [incorrect]compile-flags:--test --test-run-directory={{src-base}}/coverage -Zunstable-options
+// [correct]compile-flags:--test --test-run-directory={{src-base}}
+// [incorrect]compile-flags:--test --test-run-directory={{src-base}}/coverage
 // normalize-stdout-test: "tests/rustdoc-ui" -> "$$DIR"
 // normalize-stdout-test "finished in \d+\.\d+s" -> "finished in $$TIME"