Rollup merge of rust-lang#129134 - lolbinarycat:continue-at, r=Kobzol

bootstrap: improve error recovery flags to curl

alternative to rust-lang#128459

fixes rust-lang#110178

r? ```@Kobzol```

src/bootstrap/bootstrap.py

@@ -79,6 +79,11 @@ def get(base, url, path, checksums, verbose=False):
                 eprint("removing", temp_path)
             os.unlink(temp_path)
 
+def curl_version():
+    m = re.match(bytes("^curl ([0-9]+)\\.([0-9]+)", "utf8"), require(["curl", "-V"]))
+    if m is None:
+        return (0, 0)
+    return (int(m[1]), int(m[2]))
 
 def download(path, url, probably_big, verbose):
     for _ in range(4):
@@ -107,11 +112,15 @@ def _download(path, url, probably_big, verbose, exception):
         # If curl is not present on Win32, we should not sys.exit
         #   but raise `CalledProcessError` or `OSError` instead
         require(["curl", "--version"], exception=platform_is_win32())
-        run(["curl", option,
+        extra_flags = []
+        if curl_version() > (7, 70):
+            extra_flags = [ "--retry-all-errors" ]
+        run(["curl", option] + extra_flags + [
             "-L", # Follow redirect.
             "-y", "30", "-Y", "10",    # timeout if speed is < 10 bytes/sec for > 30 seconds
             "--connect-timeout", "30",  # timeout if cannot connect within 30 seconds
             "-o", path,
+            "--continue-at", "-",
             "--retry", "3", "-SRf", url],
             verbose=verbose,
             exception=True, # Will raise RuntimeError on failure

src/bootstrap/src/core/download.rs

@@ -22,6 +22,24 @@ fn try_run(config: &Config, cmd: &mut Command) -> Result<(), ()> {
     config.try_run(cmd)
 }
 
+fn extract_curl_version(out: &[u8]) -> semver::Version {
+    let out = String::from_utf8_lossy(out);
+    // The output should look like this: "curl <major>.<minor>.<patch> ..."
+    out.lines()
+        .next()
+        .and_then(|line| line.split(" ").nth(1))
+        .and_then(|version| semver::Version::parse(version).ok())
+        .unwrap_or(semver::Version::new(1, 0, 0))
+}
+
+fn curl_version() -> semver::Version {
+    let mut curl = Command::new("curl");
+    curl.arg("-V");
+    let Ok(out) = curl.output() else { return semver::Version::new(1, 0, 0) };
+    let out = out.stdout;
+    extract_curl_version(&out)
+}
+
 /// Generic helpers that are useful anywhere in bootstrap.
 impl Config {
     pub fn is_verbose(&self) -> bool {
@@ -220,6 +238,8 @@ impl Config {
             "30", // timeout if cannot connect within 30 seconds
             "-o",
             tempfile.to_str().unwrap(),
+            "--continue-at",
+            "-",
             "--retry",
             "3",
             "-SRf",
@@ -230,6 +250,10 @@ impl Config {
         } else {
             curl.arg("--progress-bar");
         }
+        // --retry-all-errors was added in 7.71.0, don't use it if curl is old.
+        if curl_version() >= semver::Version::new(7, 71, 0) {
+            curl.arg("--retry-all-errors");
+        }
         curl.arg(url);
         if !self.check_run(&mut curl) {
             if self.build.contains("windows-msvc") {