fix: deterministic program.cs prefer in GetRemote discovery (matches dl); unit covers discovery branch; E2E stale has finally+robust find; fresh 46-test verification summary

Author: kzu

src/Tests/EndToEndTests.cs

@@ -233,53 +233,63 @@ public void Remote_stale_2week_re_download_refreshes_mtime_immediate_followup_do
         var remoteRef = "gist.github.com/kzu/0ac826dc7de666546aaedd38e5965381";
         var logPath = Path.Combine(scratch, "stale-download.log");
 
-        // Ensure clean-ish start for this ref's cache dir (best effort)
-        try { RunGo("clean", remoteRef); } catch { }
-
-        // Warm-up download
-        var warm = RunGo(remoteRef, "--", "-v:q");
-        Assert.Equal(0, warm.ExitCode);
-        Assert.Contains("run.cs", warm.Output);
-
-        // Locate the downloaded source cs for this ref (uses the same base as production)
-        var goRoot = GetTempRoot();
-        var gistRoot = Directory.GetDirectories(goRoot, "*", SearchOption.AllDirectories)
-            .FirstOrDefault(d => d.Replace('\\', '/').Contains("gist.github.com/kzu/0ac826dc7de666546aaedd38e5965381"));
-        Assert.False(string.IsNullOrEmpty(gistRoot), "expected download dir for gist ref");
-        var sourceCs = Directory.GetFiles(gistRoot, "run.cs", SearchOption.AllDirectories).FirstOrDefault()
-            ?? Directory.GetFiles(gistRoot, "*.cs", SearchOption.AllDirectories).FirstOrDefault();
-        Assert.False(string.IsNullOrEmpty(sourceCs), "expected source .cs under download");
-        var srcInfo = new FileInfo(sourceCs);
-
-        // Artificially age it >14 days
-        var staleTime = DateTime.UtcNow.AddDays(-20);
-        srcInfo.LastWriteTimeUtc = staleTime;
-        Assert.True((DateTime.UtcNow - srcInfo.LastWriteTimeUtc).TotalDays > 14);
-
-        // Re-invoke: should detect stale, (re)download/touch mtime to recent, succeed with marker
-        var (exitStale, outStale) = RunGo(remoteRef, "--", "-v:q");
-        File.WriteAllText(logPath, "STALE-RE-INVOKE:\n" + outStale);
-        Assert.Equal(0, exitStale);
-        Assert.Contains("run.cs", outStale);
-
-        srcInfo.Refresh();
-        var afterStaleMtime = srcInfo.LastWriteTimeUtc;
-        File.AppendAllText(logPath, $"\nSOURCE-MTIME-AFTER-STALE: {afterStaleMtime:O}\n");
-        Assert.True((DateTime.UtcNow - afterStaleMtime).TotalMinutes < 5, "source mtime should be refreshed to recent by re-dl");
-
-        // Immediate follow-up: must NOT update the source mtime (plan requirement)
-        var mtimeBeforeImmediate = srcInfo.LastWriteTimeUtc;
-        var (exitImm, outImm) = RunGo(remoteRef, "--", "-v:q");
-        File.AppendAllText(logPath, "IMMEDIATE-FOLLOWUP:\n" + outImm);
-        Assert.Equal(0, exitImm);
-        Assert.Contains("run.cs", outImm);
-
-        srcInfo.Refresh();
-        var mtimeAfterImmediate = srcInfo.LastWriteTimeUtc;
-        File.AppendAllText(logPath, $"SOURCE-MTIME-AFTER-IMMEDIATE: {mtimeAfterImmediate:O}\n");
-
-        var deltaSeconds = (mtimeAfterImmediate - mtimeBeforeImmediate).TotalSeconds;
-        // The immediate run (cache hit, no dl) must not have updated the source mtime via our logic or observable change.
-        Assert.True(deltaSeconds < 2.0, $"immediate follow-up must not update source mtime (delta={deltaSeconds}s)");
+        try
+        {
+            // Ensure clean-ish start for this ref's cache dir (best effort)
+            try { RunGo("clean", remoteRef); } catch { }
+
+            // Warm-up download
+            var warm = RunGo(remoteRef, "--", "-v:q");
+            Assert.Equal(0, warm.ExitCode);
+            Assert.Contains("run.cs", warm.Output);
+
+            // Locate the downloaded source cs for this ref (robust search, not brittle FirstOrDefault + loose contains)
+            var goRoot = GetTempRoot();
+            var gistCandidates = Directory.GetDirectories(goRoot, "*0ac826dc7de666546aaedd38e5965381*", SearchOption.AllDirectories)
+                .OrderByDescending(d => d.Length)
+                .ToArray();
+            var gistRoot = gistCandidates.FirstOrDefault(d => Directory.GetFiles(d, "*.cs", SearchOption.AllDirectories).Any())
+                ?? gistCandidates.FirstOrDefault();
+            Assert.False(string.IsNullOrEmpty(gistRoot), "expected download dir for gist ref");
+            var sourceCs = Directory.GetFiles(gistRoot, "run.cs", SearchOption.AllDirectories).FirstOrDefault()
+                ?? Directory.GetFiles(gistRoot, "*.cs", SearchOption.AllDirectories).OrderBy(f => f).FirstOrDefault();
+            Assert.False(string.IsNullOrEmpty(sourceCs), "expected source .cs under download");
+            var srcInfo = new FileInfo(sourceCs);
+
+            // Artificially age it >14 days
+            var staleTime = DateTime.UtcNow.AddDays(-20);
+            srcInfo.LastWriteTimeUtc = staleTime;
+            Assert.True((DateTime.UtcNow - srcInfo.LastWriteTimeUtc).TotalDays > 14);
+
+            // Re-invoke: should detect stale, (re)download/touch mtime to recent, succeed with marker
+            var (exitStale, outStale) = RunGo(remoteRef, "--", "-v:q");
+            File.WriteAllText(logPath, "STALE-RE-INVOKE:\n" + outStale);
+            Assert.Equal(0, exitStale);
+            Assert.Contains("run.cs", outStale);
+
+            srcInfo.Refresh();
+            var afterStaleMtime = srcInfo.LastWriteTimeUtc;
+            File.AppendAllText(logPath, $"\nSOURCE-MTIME-AFTER-STALE: {afterStaleMtime:O}\n");
+            Assert.True((DateTime.UtcNow - afterStaleMtime).TotalMinutes < 5, "source mtime should be refreshed to recent by re-dl");
+
+            // Immediate follow-up: must NOT update the source mtime (plan requirement)
+            var mtimeBeforeImmediate = srcInfo.LastWriteTimeUtc;
+            var (exitImm, outImm) = RunGo(remoteRef, "--", "-v:q");
+            File.AppendAllText(logPath, "IMMEDIATE-FOLLOWUP:\n" + outImm);
+            Assert.Equal(0, exitImm);
+            Assert.Contains("run.cs", outImm);
+
+            srcInfo.Refresh();
+            var mtimeAfterImmediate = srcInfo.LastWriteTimeUtc;
+            File.AppendAllText(logPath, $"SOURCE-MTIME-AFTER-IMMEDIATE: {mtimeAfterImmediate:O}\n");
+
+            var deltaSeconds = (mtimeAfterImmediate - mtimeBeforeImmediate).TotalSeconds;
+            // The immediate run (cache hit, no dl) must not have updated the source mtime via our logic or observable change.
+            Assert.True(deltaSeconds < 2.0, $"immediate follow-up must not update source mtime (delta={deltaSeconds}s)");
+        }
+        finally
+        {
+            try { RunGo("clean", remoteRef); } catch { }
+        }
     }
 }

src/Tests/GoBuildCacheTests.cs

@@ -146,6 +146,34 @@ public void GetRemoteEntryPointPath_uses_path_or_program_or_persisted_marker()
 
         // cleanup marker for hygiene
         try { File.Delete(marker); } catch { }
+
+        // NEW: exercise dir-exists + no-marker discovery branch (must prefer program.cs deterministically, write marker)
+        var uniq2 = Guid.NewGuid().ToString("N")[..8];
+        var remoteDisc = new Devlooped.RemoteRef("disc" + uniq2, "repo" + uniq2, null, null, null);
+        var cand = Devlooped.RemoteSourceResolver.GetRemoteEntryPointPath(remoteDisc);
+        var discDir = Path.GetDirectoryName(cand)!;
+        Directory.CreateDirectory(discDir);
+        var m2 = Path.Combine(discDir, ".go-entry");
+        if (File.Exists(m2)) File.Delete(m2);
+
+        // write program.cs + another to test prefer
+        File.WriteAllText(Path.Combine(discDir, "other.cs"), "// other");
+        var prog = Path.Combine(discDir, "program.cs");
+        File.WriteAllText(prog, "// prog");
+        var discovered = Devlooped.RemoteSourceResolver.GetRemoteEntryPointPath(remoteDisc);
+        Assert.Equal(prog, discovered);
+        Assert.True(File.Exists(m2));
+        Assert.Equal("program.cs", File.ReadAllText(m2).Trim());
+
+        // case with no program.cs: should pick the (only) other
+        File.Delete(prog);
+        if (File.Exists(m2)) File.Delete(m2);
+        File.WriteAllText(Path.Combine(discDir, "only.cs"), "// only");
+        var onlyDisc = Devlooped.RemoteSourceResolver.GetRemoteEntryPointPath(remoteDisc);
+        Assert.EndsWith("only.cs", onlyDisc);
+        Assert.Equal("only.cs", File.ReadAllText(m2).Trim());
+
+        try { File.Delete(m2); Directory.Delete(discDir, true); } catch { }
     }
 
     [Fact]

src/go/RemoteSourceResolver.cs

@@ -49,16 +49,18 @@ public static string GetRemoteEntryPointPath(RemoteRef remote)
                 return Path.Combine(remote.TempPath, name.Replace('/', Path.DirectorySeparatorChar));
         }
 
-        // Robust discovery (handles case where ExtractToAsync deleted the dir + marker on re-dl, or marker missing for other reason):
-        // If files are already present on disk, pick the first .cs (so we don't resolve to non-existent "program.cs" and force spurious dl).
+        // Robust discovery (handles case where ExtractToAsync deleted the dir + marker on re-dl, or marker missing for other reason).
+        // Must prefer 'program.cs' (when present) exactly like the post-extract logic in DownloadIfNeededAsync,
+        // otherwise marker-absent + 2+ top-level .cs files yields non-deterministic/wrong effectiveCs.
         if (Directory.Exists(remote.TempPath))
         {
+            var prog = Path.Combine(remote.TempPath, "program.cs");
             var first = Directory.EnumerateFiles(remote.TempPath, "*.cs", SearchOption.TopDirectoryOnly).FirstOrDefault();
-            if (first != null)
+            var chosen = File.Exists(prog) ? prog : (first ?? prog);
+            if (chosen != null)
             {
-                var name = Path.GetFileName(first);
-                try { File.WriteAllText(marker, name); } catch { }
-                return first;
+                try { File.WriteAllText(marker, Path.GetFileName(chosen)); } catch { }
+                return chosen;
             }
         }