cmd/cue: better error message for mismatched publish version

The error messages did not make it that clear what the issue was
when there's a version mismatch between the version argument
passed to `cue mod publish` and the major version in the
module file.

Example of old error message:

    cannot form module version: mismatched major version suffix in "mod.example/blah" (version v1.0.0)

Example of new message:

   publish version "v1.0.0" does not match implied major version "v0" in "cue.mod/module.cue"; must be v0.N.N

Also improve a couple of other error messages in this area, making clear that a canonical semver
is required.

Fixes #3225

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: Id84166be9e5c97216d170a8968ec44354a56cb82
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1197924
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

cmd/cue/cmd/modpublish.go

@@ -134,6 +134,21 @@ func runModUpload(cmd *Command, args []string) error {
 	if err != nil {
 		return err
 	}
+	if !semver.IsValid(args[0]) {
+		return fmt.Errorf("invalid publish version %q; must be valid semantic version (see http://semver.org)", args[0])
+	}
+	if semver.Canonical(args[0]) != args[0] {
+		return fmt.Errorf("publish version %q is not in canonical form", args[0])
+	}
+
+	if major := mf.MajorVersion(); semver.Major(args[0]) != major {
+		if _, _, ok := module.SplitPathVersion(mf.Module); ok {
+			return fmt.Errorf("publish version %q does not match the major version %q declared in %q; must be %s.N.N", args[0], major, modPath, major)
+		} else {
+			return fmt.Errorf("publish version %q does not match implied major version %q in %q; must be %s.N.N", args[0], major, modPath, major)
+		}
+	}
+
 	mv, err := module.NewVersion(mf.QualifiedModule(), args[0])
 	if err != nil {
 		return fmt.Errorf("cannot form module version: %v", err)

cmd/cue/cmd/testdata/script/modpublish_invalid_version.txtar

@@ -0,0 +1,24 @@
+memregistry MEMREGISTRY
+env CUE_REGISTRY=$MEMREGISTRY+insecure
+
+! exec cue mod publish 1.2.3
+cmp stderr want-stderr-1
+
+! exec cue mod publish v1.2
+cmp stderr want-stderr-2
+
+! exec cue mod publish v1.2.3+build
+cmp stderr want-stderr-3
+
+-- want-stderr-1 --
+invalid publish version "1.2.3"; must be valid semantic version (see http://semver.org)
+-- want-stderr-2 --
+publish version "v1.2" is not in canonical form
+-- want-stderr-3 --
+publish version "v1.2.3+build" is not in canonical form
+-- cue.mod/module.cue --
+module: "test.example"
+language: version: "v0.9.2"
+-- main.cue --
+package main
+

cmd/cue/cmd/testdata/script/modpublish_no_major_suffix.txtar

@@ -14,9 +14,9 @@ exec cue mod publish v0.0.1
 
 # The inferred version is v0. Using any other major version will fail.
 ! exec cue mod publish v1.0.0
-stderr 'mismatched major version suffix'
+stderr 'publish version "v1.0.0" does not match implied major version "v0" in ".*module.cue"; must be v0.N.N'
 ! exec cue mod publish v2.0.0
-stderr 'mismatched major version suffix'
+stderr 'publish version "v2.0.0" does not match implied major version "v0" in ".*module.cue"; must be v0.N.N'
 
 # `cue mod fix` will not add add a major version suffix when missing.
 exec cue mod fix
@@ -28,9 +28,9 @@ cmp cue.mod/module.cue cue.mod/module.cue.edited-with-v0
 
 # Trying to publish with the wrong major version will fail.
 ! exec cue mod publish v1.0.0
-stderr 'mismatched major version suffix'
+stderr 'publish version "v1.0.0" does not match the major version "v0" declared in ".*module.cue"; must be v0.N.N'
 ! exec cue mod publish v2.0.0
-stderr 'mismatched major version suffix'
+stderr 'publish version "v2.0.0" does not match the major version "v0" declared in ".*module.cue"; must be v0.N.N'
 
 # Publishing with the right major version works.
 exec cue mod publish v0.0.2