cmd/go/internal/modget: diagnose missing transitive dependencies

For #41315

Change-Id: I3989bcb051ae57dd2d8f89759d241d4cdce49659
Reviewed-on: https://go-review.googlesource.com/c/go/+/255969
Trust: Bryan C. Mills <bcmills@google.com>
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

8 files changed, 149 insertions, 8 deletions

diff --git a/src/cmd/go/internal/modget/get.go b/src/cmd/go/internal/modget/get.go
index 52e3ec84fb..7e573bacb7 100644
--- a/src/cmd/go/internal/modget/get.go
+++ b/src/cmd/go/internal/modget/get.go
@@ -482,14 +482,6 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 		}
 		prevBuildList = buildList
 	}
-	if *getD {
-		// Only print warnings after the last iteration, and only if we aren't going
-		// to build (to avoid doubled warnings).
-		//
-		// Only local patterns in the main module, such as './...', can be unmatched.
-		// (See the mod_get_nopkgs test for more detail.)
-		search.WarnUnmatched(matches)
-	}
 
 	// Handle downgrades.
 	var down []module.Version
@@ -579,6 +571,23 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 		base.Fatalf("%v", buf.String())
 	}
 
+	if len(pkgPatterns) > 0 || len(args) == 0 {
+		// Before we write the updated go.mod file, reload the requested packages to
+		// check for errors.
+		loadOpts := modload.PackageOpts{
+			Tags:      imports.AnyTags(),
+			LoadTests: *getT,
+
+			// Only print warnings after the last iteration, and only if we aren't going
+			// to build (to avoid doubled warnings).
+			//
+			// Only local patterns in the main module, such as './...', can be unmatched.
+			// (See the mod_get_nopkgs test for more detail.)
+			SilenceUnmatchedWarnings: !*getD,
+		}
+		modload.LoadPackages(ctx, loadOpts, pkgPatterns...)
+	}
+
 	// Everything succeeded. Update go.mod.
 	modload.AllowWriteGoMod()
 	modload.WriteGoMod()
diff --git a/src/cmd/go/testdata/mod/example.com_retract_rename_v1.0.0-bad.txt b/src/cmd/go/testdata/mod/example.com_retract_rename_v1.0.0-bad.txt
index 49364751d8..25c4ff1b1f 100644
--- a/src/cmd/go/testdata/mod/example.com_retract_rename_v1.0.0-bad.txt
+++ b/src/cmd/go/testdata/mod/example.com_retract_rename_v1.0.0-bad.txt
@@ -8,3 +8,9 @@ is added for the first time with a custom module path.
 module example.com/retract/rename
 
 go 1.16
+-- go.mod --
+module example.com/retract/rename
+
+go 1.16
+-- rename.go --
+package rename
diff --git a/src/cmd/go/testdata/mod/example.com_retract_rename_v1.9.0-new.txt b/src/cmd/go/testdata/mod/example.com_retract_rename_v1.9.0-new.txt
index fcbdfdaf94..9c08f713c4 100644
--- a/src/cmd/go/testdata/mod/example.com_retract_rename_v1.9.0-new.txt
+++ b/src/cmd/go/testdata/mod/example.com_retract_rename_v1.9.0-new.txt
@@ -11,3 +11,12 @@ go 1.16
 
 // bad
 retract v1.0.0-bad
+-- go.mod --
+module example.com/retract/newname
+
+go 1.16
+
+// bad
+retract v1.0.0-bad
+-- newname.go --
+package newname
diff --git a/src/cmd/go/testdata/mod/example.net_pkgadded_v1.0.0.txt b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.0.0.txt
new file mode 100644
index 0000000000..207e86a73c
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.0.0.txt
@@ -0,0 +1,17 @@
+Written by hand.
+Test module with a root package added in v1.1.0
+and a subpackage added in v1.2.0.
+
+-- .mod --
+module example.net/pkgadded
+
+go 1.16
+-- .info --
+{"Version":"v1.0.0"}
+-- go.mod --
+module example.net/pkgadded
+
+go 1.16
+-- README.txt --
+We will add the package example.net/pkgadded in v1.1.0,
+and example.net/pkgadded/subpkg in v1.2.0.
diff --git a/src/cmd/go/testdata/mod/example.net_pkgadded_v1.1.0.txt b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.1.0.txt
new file mode 100644
index 0000000000..1c88de2dd6
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.1.0.txt
@@ -0,0 +1,19 @@
+Written by hand.
+Test module with a root package added in v1.1.0
+and a subpackage added in v1.2.0.
+
+-- .mod --
+module example.net/pkgadded
+
+go 1.16
+-- .info --
+{"Version":"v1.1.0"}
+-- go.mod --
+module example.net/pkgadded
+
+go 1.16
+-- README.txt --
+We will add the package example.net/pkgadded/subpkg in v1.2.0.
+-- pkgadded.go --
+// Package pkgadded was added in v1.1.0.
+package pkgadded
diff --git a/src/cmd/go/testdata/mod/example.net_pkgadded_v1.2.0.txt b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.2.0.txt
new file mode 100644
index 0000000000..922951ac37
--- /dev/null
+++ b/src/cmd/go/testdata/mod/example.net_pkgadded_v1.2.0.txt
@@ -0,0 +1,20 @@
+Written by hand.
+Test module with a root package added in v1.1.0
+and a subpackage added in v1.2.0.
+
+-- .mod --
+module example.net/pkgadded
+
+go 1.16
+-- .info --
+{"Version":"v1.2.0"}
+-- go.mod --
+module example.net/pkgadded
+
+go 1.16
+-- pkgadded.go --
+// Package pkgadded was added in v1.1.0.
+package pkgadded
+-- subpkg/subpkg.go --
+// Package subpkg was added in v1.2.0.
+package subpkg
diff --git a/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt b/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt
new file mode 100644
index 0000000000..53b789ecc5
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_get_downgrade_missing.txt
@@ -0,0 +1,33 @@
+cp go.mod go.mod.orig
+
+# getting a specific version of a module along with a pattern
+# not yet present in that module should report the version mismatch
+# rather than a "matched no packages" warning.
+! go get example.net/pkgadded@v1.1.0 example.net/pkgadded/subpkg/...
+stderr '^go get: conflicting versions for module example\.net/pkgadded: v1\.1\.0 and v1\.2\.0$'
+! stderr 'matched no packages'
+cmp go.mod.orig go.mod
+
+! go get example.net/pkgadded/...@v1.0.0
+stderr '^go get example\.net/pkgadded/\.\.\.@v1\.0\.0: module example\.net/pkgadded@v1\.0\.0 found, but does not contain packages matching example\.net/pkgadded/\.\.\.$'
+cmp go.mod.orig go.mod
+
+! go get example.net/pkgadded@v1.0.0 .
+stderr -count=1 '^go: found example.net/pkgadded/subpkg in example.net/pkgadded v1\.2\.0$'  # TODO: We shouldn't even try v1.2.0.
+stderr '^example.com/m imports\n\texample.net/pkgadded/subpkg: import missing'  # TODO: better error message
+cmp go.mod.orig go.mod
+
+go get example.net/pkgadded@v1.0.0
+! go list -deps -mod=readonly .
+stderr '^m.go:3:8: cannot find module providing package example\.net/pkgadded/subpkg: '
+
+-- go.mod --
+module example.com/m
+
+go 1.16
+
+require example.net/pkgadded v1.2.0
+-- m.go --
+package m
+
+import _ "example.net/pkgadded/subpkg"
diff --git a/src/cmd/go/testdata/script/mod_get_errors.txt b/src/cmd/go/testdata/script/mod_get_errors.txt
new file mode 100644
index 0000000000..5b1b8367bb
--- /dev/null
+++ b/src/cmd/go/testdata/script/mod_get_errors.txt
@@ -0,0 +1,28 @@
+cp go.mod go.mod.orig
+
+! go get
+stderr '^example.com/m imports\n\texample.com/badimport imports\n\texample.net/oops: import missing$'  # TODO: better error message
+cmp go.mod.orig go.mod
+
+! go get -d
+stderr '^example.com/m imports\n\texample.com/badimport imports\n\texample.net/oops: import missing$'  # TODO: better error message
+cmp go.mod.orig go.mod
+
+-- go.mod --
+module example.com/m
+
+go 1.16
+
+replace example.com/badimport v0.1.0 => ./badimport
+-- m.go --
+package m
+
+import _ "example.com/badimport"
+-- badimport/go.mod --
+module example.com/badimport
+
+go 1.16
+-- badimport/badimport.go --
+package badimport
+
+import "example.net/oops"