cmd/cue: find packages by canonical path in get go

Most Go APIs like go/types.Package.Path and go/packages.Package.PkgPath
use full canonical package paths, whereas go/packages.Package.Imports
uses source import paths as they appear in the import declarations.

We mixed the two, using paths from go/types to index into Imports,
resulting in nil packages in the edge cases when they are different.
One such instance is vendored packages, whose full path may be
"vendor/foo/bar" when they are simply imported as "foo/bar".

This also fixes a similar panic with some type aliases,
in particular when an alias points to an indirectly imported package,
as such a package would be missing from the Imports map.

The two added testscripts reproduced both panics without the fix,
and now work as expected with the fix.

Fixes #1607.
Fixes #2046.

Change-Id: I51df3465da76b39f031855982b48552604817f80
Signed-off-by: Thomas Way <thomas@6f.io>
Co-authored-by: Daniel Martí <mvdan@mvdan.cc>
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1173100
Reviewed-by: Paul Jolly <paul@myitcv.io>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
TryBot-Result: CUEcueckoo <cueckoo@gmail.com>
(cherry picked from commit b648cf4)
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1190977
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cmd/cue/cmd/get_go.go

@@ -246,9 +246,10 @@ func (e *extractor) filter(name string) bool {
 type extractor struct {
 	cmd *Command
 
-	stderr io.Writer
-	pkgs   []*packages.Package
-	done   map[string]bool
+	stderr  io.Writer
+	pkgs    []*packages.Package
+	allPkgs map[string]*packages.Package
+	done    map[string]bool
 
 	// per package
 	orig     map[types.Type]*ast.StructType
@@ -395,10 +396,11 @@ func extract(cmd *Command, args []string) error {
 	}
 
 	e := extractor{
-		cmd:    cmd,
-		stderr: cmd.Stderr(),
-		pkgs:   pkgs,
-		orig:   map[types.Type]*ast.StructType{},
+		cmd:     cmd,
+		stderr:  cmd.Stderr(),
+		pkgs:    pkgs,
+		allPkgs: map[string]*packages.Package{},
+		orig:    map[types.Type]*ast.StructType{},
 	}
 
 	e.initExclusions(flagExclude.String(cmd))
@@ -407,6 +409,7 @@ func extract(cmd *Command, args []string) error {
 
 	for _, p := range pkgs {
 		e.done[p.PkgPath] = true
+		e.addPackage(p)
 	}
 
 	for _, p := range pkgs {
@@ -417,6 +420,19 @@ func extract(cmd *Command, args []string) error {
 	return nil
 }
 
+func (e *extractor) addPackage(p *packages.Package) {
+	if pkg, ok := e.allPkgs[p.PkgPath]; ok {
+		if p != pkg {
+			panic(fmt.Sprintf("duplicate package %s", p.PkgPath))
+		}
+		return
+	}
+	e.allPkgs[p.PkgPath] = p
+	for _, pkg := range p.Imports {
+		e.addPackage(pkg)
+	}
+}
+
 func (e *extractor) recordTypeInfo(p *packages.Package) {
 	for _, f := range p.Syntax {
 		ast.Inspect(f, func(n ast.Node) bool {
@@ -546,8 +562,7 @@ func (e *extractor) extractPkg(root string, p *packages.Package) error {
 	for path := range e.usedPkgs {
 		if !e.done[path] {
 			e.done[path] = true
-			p := p.Imports[path]
-			if err := e.extractPkg(root, p); err != nil {
+			if err := e.extractPkg(root, e.allPkgs[p.PkgPath]); err != nil {
 				return err
 			}
 		}

cmd/cue/cmd/testdata/script/get_go_type_alias.txtar

@@ -0,0 +1,38 @@
+# Issue 1607
+
+exec cue get go --local ./x
+cmp x/x_go_gen.cue x_go_gen.cue.golden
+
+-- go.mod --
+module mod.test
+
+go 1.21
+-- x/x.go --
+package x
+
+import "mod.test/y"
+
+type X = y.Y
+
+-- y/y.go --
+package y
+
+import "mod.test/z"
+
+type Y = z.Z
+
+-- z/z.go --
+package z
+
+type Z int
+
+-- x_go_gen.cue.golden --
+// Code generated by cue get go. DO NOT EDIT.
+
+//cue:generate cue get go mod.test/x
+
+package x
+
+import "mod.test/z"
+
+#X: z.#Z

cmd/cue/cmd/testdata/script/get_go_vendor.txtar

@@ -0,0 +1,38 @@
+# Issue 1607
+
+exec cue get go --local ./x
+cmp x/x_go_gen.cue x_go_gen.cue.golden
+
+-- go.mod --
+module mod.test
+
+go 1.21
+-- x/x.go --
+package x
+
+import "mod.test/y"
+
+type X = y.Y
+
+-- y/y.go --
+package y
+
+import "mod.test/z"
+
+type Y = z.Z
+
+-- z/z.go --
+package z
+
+type Z int
+
+-- x_go_gen.cue.golden --
+// Code generated by cue get go. DO NOT EDIT.
+
+//cue:generate cue get go mod.test/x
+
+package x
+
+import "mod.test/z"
+
+#X: z.#Z