cmd/go: clarify error when package is removed in a module

If no module in the build list provides an imported package, we
try to upgrade to the "@latest" version. If there is a requirement on
a version of the module which is newer than the "@latest" version
(e.g., a prerelease or pseudoversion), we cannot upgrade further.

We previously reported "looping trying to add package" when we saw the
package in "@latest" but it was removed later. The meaning of this is
unclear for users, so with this change, we explain the package was
removed.

Fixes #30394

Change-Id: I1b7fec2c37e762fb600e66ee8a4df4aeaf13e67a
Reviewed-on: https://go-review.googlesource.com/c/go/+/169720
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index 83ef0e0b4fd78b0ab5b1063e667c64a411618caa..305e0ddb752edab53306e6089457799a6a20a8ce 100644 (file)
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -28,6 +28,10 @@ import (
 type ImportMissingError struct {
        ImportPath string
        Module     module.Version
+
+       // newMissingVersion is set to a newer version of Module if one is present
+       // in the build list. When set, we can't automatically upgrade.
+       newMissingVersion string
 }
 
 func (e *ImportMissingError) Error() string {
@@ -189,7 +193,18 @@ func Import(path string) (m module.Version, dir string, err error) {
                }
                return module.Version{}, "", &ImportMissingError{ImportPath: path}
        }
-       return m, "", &ImportMissingError{ImportPath: path, Module: m}
+       newMissingVersion := ""
+       for _, bm := range buildList {
+               if bm.Path == m.Path && semver.Compare(bm.Version, m.Version) > 0 {
+                       // This typically happens when a package is present at the "@latest"
+                       // version (e.g., v1.0.0) of a module, but we have a newer version
+                       // of the same module in the build list (e.g., v1.0.1-beta), and
+                       // the package is not present there.
+                       newMissingVersion = bm.Version
+                       break
+               }
+       }
+       return m, "", &ImportMissingError{ImportPath: path, Module: m, newMissingVersion: newMissingVersion}
 }
 
 // maybeInModule reports whether, syntactically,

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 71b7308c0da3bec4a6c159417db2c1eeb3750cdd..57c2dd25a622b53b61c4e1e72a1e0910ca74a6e5 100644 (file)
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -547,6 +547,9 @@ func (ld *loader) load(roots func() []string) {
                }
                for _, pkg := range ld.pkgs {
                        if err, ok := pkg.err.(*ImportMissingError); ok && err.Module.Path != "" {
+                               if err.newMissingVersion != "" {
+                                       base.Fatalf("go: %s: package provided by %s at latest version %s but not at required version %s", pkg.stackText(), err.Module.Path, err.Module.Version, err.newMissingVersion)
+                               }
                                if added[pkg.path] {
                                        base.Fatalf("go: %s: looping trying to add package", pkg.stackText())
                                }

diff --git a/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.0.txt b/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.0.txt
new file mode 100644 (file)
index 0000000..15f3f69
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.0.txt
@@ -0,0 +1,11 @@
+The deprecated package is present in this version (which is @latest) but
+is deleted in a newer prerelease version.
+
+-- .mod --
+module example.com/missingpkg
+-- .info --
+{"Version":"v1.0.0"}
+-- lib.go --
+package lib
+-- deprecated/deprecated.go --
+package deprecated

diff --git a/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.1-beta.txt b/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.1-beta.txt
new file mode 100644 (file)
index 0000000..44580fe
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.com_missingpkg_v1.0.1-beta.txt
@@ -0,0 +1,8 @@
+The deprecated package is deleted in this version.
+
+-- .mod --
+module example.com/missingpkg
+-- .info --
+{"Version":"v1.0.1-beta"}
+-- lib.go --
+package lib

diff --git a/src/cmd/go/testdata/mod/example.com_usemissingpre_v1.0.0.txt b/src/cmd/go/testdata/mod/example.com_usemissingpre_v1.0.0.txt
new file mode 100644 (file)
index 0000000..5e1c5c8
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.com_usemissingpre_v1.0.0.txt
@@ -0,0 +1,13 @@
+This module requires example.com/missingpkg at a prerelease version, which
+is newer than @latest.
+
+-- .mod --
+module example.com/usemissingpre
+
+require example.com/missingpkg v1.0.1-beta
+-- .info --
+{"Version":"v1.0.0"}
+-- use.go --
+package use
+
+import _ "example.com/missingpkg"

diff --git a/src/cmd/go/testdata/script/mod_missingpkg_prerelease.txt b/src/cmd/go/testdata/script/mod_missingpkg_prerelease.txt
new file mode 100644 (file)
index 0000000..e7409d1
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_missingpkg_prerelease.txt
@@ -0,0 +1,12 @@
+env GO111MODULE=on
+
+! go list use.go
+stderr 'import "example.com/missingpkg/deprecated": package provided by example.com/missingpkg at latest version v1.0.0 but not at required version v1.0.1-beta'
+
+-- use.go --
+package use
+
+import (
+       _ "example.com/missingpkg/deprecated"
+       _ "example.com/usemissingpre"
+)