Correctly handle update across missing nightlies

Fixes #2001.

Author: jonhoo

src/dist/dist.rs

@@ -629,6 +629,9 @@ fn update_from_dist_<'a>(
                     if first_err.is_none() {
                         first_err = Some(e);
                     }
+                } else if let ErrorKind::MissingReleaseForToolchain(..) = e.kind() {
+                    // no need to even print anything for missing nightlies,
+                    // since we don't really "skip" them
                 } else if let Some(e) = first_err {
                     // if we fail to find a suitable nightly, we abort the search and give the
                     // original "components unavailable for download" error.
@@ -721,7 +724,9 @@ fn try_update_from_dist_<'a>(
     let manifest = match dl_v1_manifest(download, toolchain) {
         Ok(m) => m,
         Err(Error(crate::ErrorKind::DownloadNotExists { .. }, _)) => {
-            return Err(format!("no release found for '{}'", toolchain.manifest_name()).into());
+            return Err(Error::from(ErrorKind::MissingReleaseForToolchain(
+                toolchain.manifest_name(),
+            )));
         }
         Err(e @ Error(ErrorKind::ChecksumFailed { .. }, _)) => {
             return Err(e);

src/errors.rs

@@ -275,6 +275,10 @@ error_chain! {
             description("missing package for the target of a rename")
             display("server sent a broken manifest: missing package for the target of a rename {}", name)
         }
+        MissingReleaseForToolchain(name: String) {
+            description("missing release for a toolchain")
+            display("no release found for '{}'", name)
+        }
         RequestedComponentsUnavailable(c: Vec<Component>, manifest: Manifest, toolchain: String) {
             description("some requested components are unavailable to download")
             display("{}", component_unavailable_msg(&c, &manifest, &toolchain))

tests/cli-misc.rs

@@ -771,14 +771,16 @@ fn update_nightly_even_with_incompat() {
 
 #[test]
 fn nightly_backtrack_skips_missing() {
-    clitools::setup(Scenario::Unavailable, &|config| {
-        set_current_dist_date(config, "2015-01-01");
+    clitools::setup(Scenario::MissingNightly, &|config| {
+        set_current_dist_date(config, "2019-09-16");
         expect_ok(config, &["rustup", "default", "nightly"]);
 
         expect_stdout_ok(config, &["rustc", "--version"], "hash-nightly-1");
+        expect_ok(config, &["rustup", "component", "add", "rls"]);
+        expect_component_executable(config, "rls");
 
-        // nightly is missing on latest
-        set_current_dist_date(config, "2015-01-02");
+        // rls is missing on latest, nightly is missing on second-to-latest
+        set_current_dist_date(config, "2019-09-18");
 
         // update should not change nightly, and should not error
         expect_ok(config, &["rustup", "update", "nightly", "--no-self-update"]);

tests/mock/clitools.rs

@@ -52,6 +52,7 @@ pub enum Scenario {
     Unavailable,      // Two dates, v2 manifests, everything unavailable in second date.
     UnavailableRls,   // Two dates, v2 manifests, RLS unavailable in first date, restored on second.
     MissingComponent, // Three dates, v2 manifests, RLS available in first and last, not middle
+    MissingNightly,   // Three dates, v2 manifests, RLS available in first, middle missing nightly
 }
 
 pub static CROSS_ARCH1: &str = "x86_64-unknown-linux-musl";
@@ -564,6 +565,11 @@ fn create_mock_dist_server(path: &Path, s: Scenario) {
             Release::new("nightly", "1.37.0", "2019-09-13", "2"),
             Release::new("nightly", "1.37.0", "2019-09-14", "3").with_rls(RlsStatus::Unavailable),
         ],
+        Scenario::MissingNightly => vec![
+            Release::new("nightly", "1.37.0", "2019-09-16", "1"),
+            Release::stable("1.37.0", "2019-09-17"),
+            Release::new("nightly", "1.37.0", "2019-09-18", "2").with_rls(RlsStatus::Unavailable),
+        ],
         Scenario::Unavailable => vec![
             Release::new("nightly", "1.2.0", "2015-01-01", "1"),
             Release::beta("1.1.0", "2015-01-01"),
@@ -606,6 +612,7 @@ fn create_mock_dist_server(path: &Path, s: Scenario) {
         | Scenario::MultiHost
         | Scenario::Unavailable
         | Scenario::UnavailableRls
+        | Scenario::MissingNightly
         | Scenario::MissingComponent => vec![ManifestVersion::V2],
     };