[release-branch.go1.16] cmd/go/internal/load: always set IsImportCycle when in a...

When hitting an import cycle in reusePackage, and there is already
an error set, make sure IsImportCycle is set so that we don't
end up stuck in a loop.

Updates #25830
Fixes #47348

Change-Id: Iba966aea4a637dfc34ee22782a477209ac48c9bd
Reviewed-on: https://go-review.googlesource.com/c/go/+/301289
Trust: Roland Shoemaker <roland@golang.org>
Run-TryBot: Roland Shoemaker <roland@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
(cherry picked from commit cdd08e615a9b92742b21a94443720b6d70452510)
Reviewed-on: https://go-review.googlesource.com/c/go/+/336649
Trust: Bryan C. Mills <bcmills@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 8b12faf4cd2e51d8665a838c68275dce87cba018..61fde895f85b24166afc338d391b90992476f68b 100644 (file)
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -1323,6 +1323,11 @@ func reusePackage(p *Package, stk *ImportStack) *Package {
                                Err:           errors.New("import cycle not allowed"),
                                IsImportCycle: true,
                        }
+               } else if !p.Error.IsImportCycle {
+                       // If the error is already set, but it does not indicate that
+                       // we are in an import cycle, set IsImportCycle so that we don't
+                       // end up stuck in a loop down the road.
+                       p.Error.IsImportCycle = true
                }
                p.Incomplete = true
        }

diff --git a/src/cmd/go/testdata/script/list_err_cycle.txt b/src/cmd/go/testdata/script/list_err_cycle.txt
new file mode 100644 (file)
index 0000000..44b82a6
--- /dev/null
+++ b/src/cmd/go/testdata/script/list_err_cycle.txt
@@ -0,0 +1,15 @@
+# Check that we don't get infinite recursion when loading a package with
+# an import cycle and another error. Verifies #25830.
+! go list
+stderr 'found packages a \(a.go\) and b \(b.go\)'
+
+-- go.mod --
+module errcycle
+
+go 1.16
+-- a.go --
+package a
+
+import _ "errcycle"
+-- b.go --
+package b
\ No newline at end of file