Add tests for new rustdoc fingerprint behavior.

Author: ehuss

tests/testsuite/doc.rs

@@ -4,7 +4,7 @@ use cargo::core::compiler::RustDocFingerprint;
 use cargo_test_support::paths::CargoPathExt;
 use cargo_test_support::registry::Package;
 use cargo_test_support::{basic_lib_manifest, basic_manifest, git, project};
-use cargo_test_support::{is_nightly, rustc_host};
+use cargo_test_support::{is_nightly, rustc_host, symlink_supported};
 use std::fs;
 use std::str;
 
@@ -1889,3 +1889,61 @@ LLVM version: 9.0
         (String::from_utf8_lossy(&output.stdout).as_ref())
     );
 }
+
+#[cargo_test]
+fn doc_fingerprint_unusual_behavior() {
+    // Checks for some unusual circumstances with clearing the doc directory.
+    if !symlink_supported() {
+        return;
+    }
+    let p = project().file("src/lib.rs", "").build();
+    p.build_dir().mkdir_p();
+    let real_doc = p.root().join("doc");
+    real_doc.mkdir_p();
+    let build_doc = p.build_dir().join("doc");
+    p.symlink(&real_doc, &build_doc);
+    fs::write(real_doc.join("somefile"), "test").unwrap();
+    fs::write(real_doc.join(".hidden"), "test").unwrap();
+    p.cargo("doc").run();
+    // Make sure for the first run, it does not delete any files and does not
+    // break the symlink.
+    assert!(build_doc.join("somefile").exists());
+    assert!(real_doc.join("somefile").exists());
+    assert!(real_doc.join(".hidden").exists());
+    assert!(real_doc.join("foo/index.html").exists());
+    // Pretend that the last build was generated by an older version.
+    p.change_file(
+        "target/.rustdoc_fingerprint.json",
+        "{\"rustc_vv\": \"I am old\"}",
+    );
+    // Change file to trigger a new build.
+    p.change_file("src/lib.rs", "// changed");
+    p.cargo("doc")
+        .with_stderr(
+            "[DOCUMENTING] foo [..]\n\
+             [FINISHED] [..]",
+        )
+        .run();
+    // This will delete somefile, but not .hidden.
+    assert!(!real_doc.join("somefile").exists());
+    assert!(real_doc.join(".hidden").exists());
+    assert!(real_doc.join("foo/index.html").exists());
+    // And also check the -Z flag behavior.
+    p.change_file(
+        "target/.rustdoc_fingerprint.json",
+        "{\"rustc_vv\": \"I am old\"}",
+    );
+    // Change file to trigger a new build.
+    p.change_file("src/lib.rs", "// changed2");
+    fs::write(real_doc.join("somefile"), "test").unwrap();
+    p.cargo("doc -Z skip-rustdoc-fingerprint")
+        .masquerade_as_nightly_cargo()
+        .with_stderr(
+            "[DOCUMENTING] foo [..]\n\
+             [FINISHED] [..]",
+        )
+        .run();
+    // Should not have deleted anything.
+    assert!(build_doc.join("somefile").exists());
+    assert!(real_doc.join("somefile").exists());
+}