cmd/cue: parse module.cue file in non-strict mode

We do not want to prevent editing a module.cue file
when the strictness criteria are not met.

Fixes #3211.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I31991846db9a1815eeaa4cc41720e0943e74e4a0
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1196180
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1196234
Reviewed-by: Paul Jolly <paul@myitcv.io>

cmd/cue/cmd/modedit.go

@@ -77,7 +77,7 @@ func (c *modEditCmd) run(cmd *Command, args []string) error {
 	if err != nil {
 		return err
 	}
-	mf, err := modfile.Parse(data, modPath)
+	mf, err := modfile.ParseNonStrict(data, modPath)
 	if err != nil {
 		return err
 	}

cmd/cue/cmd/testdata/script/modedit_nonstrict.txtar

@@ -1,12 +1,22 @@
 # This test checks that cue mod edit works OK even when the
 # module file doesn't conform to the strict parsing.
-# TODO fix this to pass.
-! exec cue mod edit --source self
-cmpenv stderr want-stderr
+exec cue mod edit --source self
+cmp cue.mod/module.cue want-module
 
 -- cue.mod/module.cue --
 module: "main.org"
 deps: "foo.com": v: "v1.2.3"
 language: version: "v0.9.0-alpha.0"
--- want-stderr --
-invalid module.cue file $WORK${/}cue.mod${/}module.cue: no major version in "foo.com"
+-- want-module --
+module: "main.org"
+language: {
+	version: "v0.9.0-alpha.0"
+}
+source: {
+	kind: "self"
+}
+deps: {
+	"foo.com": {
+		v: "v1.2.3"
+	}
+}