cmd/guru: add workaround to handle inconsistency between go/types and gc

Add identical workaround from gorename to guru. Only affects queries
that typecheck the code first.

Fixes golang/go#16530

Change-Id: I718cfceb8d26868eea9128c8873b164333c50f53
Reviewed-on: https://go-review.googlesource.com/33359
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/guru/callees.go

@@ -28,7 +28,7 @@ func callees(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}

cmd/guru/callers.go

@@ -27,7 +27,7 @@ func callers(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}

cmd/guru/callstack.go

@@ -35,7 +35,7 @@ func callstack(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}

cmd/guru/guru.go

@@ -21,6 +21,7 @@ import (
 	"io"
 	"log"
 	"path/filepath"
+	"strings"
 
 	"golang.org/x/tools/go/ast/astutil"
 	"golang.org/x/tools/go/buildutil"
@@ -255,6 +256,53 @@ func parseQueryPos(lprog *loader.Program, pos string, needExact bool) (*queryPos
 
 // ---------- Utilities ----------
 
+// loadWithSoftErrors calls lconf.Load, suppressing "soft" errors.  (See Go issue 16530.)
+// TODO(adonovan): Once the loader has an option to allow soft errors,
+// replace calls to loadWithSoftErrors with loader calls with that parameter.
+func loadWithSoftErrors(lconf *loader.Config) (*loader.Program, error) {
+	lconf.AllowErrors = true
+
+	// Ideally we would just return conf.Load() here, but go/types
+	// reports certain "soft" errors that gc does not (Go issue 14596).
+	// As a workaround, we set AllowErrors=true and then duplicate
+	// the loader's error checking but allow soft errors.
+	// It would be nice if the loader API permitted "AllowErrors: soft".
+	prog, err := lconf.Load()
+	if err != nil {
+		return nil, err
+	}
+	var errpkgs []string
+	// Report hard errors in indirectly imported packages.
+	for _, info := range prog.AllPackages {
+		if containsHardErrors(info.Errors) {
+			errpkgs = append(errpkgs, info.Pkg.Path())
+		} else {
+			// Enable SSA construction for packages containing only soft errors.
+			info.TransitivelyErrorFree = true
+		}
+	}
+	if errpkgs != nil {
+		var more string
+		if len(errpkgs) > 3 {
+			more = fmt.Sprintf(" and %d more", len(errpkgs)-3)
+			errpkgs = errpkgs[:3]
+		}
+		return nil, fmt.Errorf("couldn't load packages due to errors: %s%s",
+			strings.Join(errpkgs, ", "), more)
+	}
+	return prog, err
+}
+
+func containsHardErrors(errors []error) bool {
+	for _, err := range errors {
+		if err, ok := err.(types.Error); ok && err.Soft {
+			continue
+		}
+		return true
+	}
+	return false
+}
+
 // allowErrors causes type errors to be silently ignored.
 // (Not suitable if SSA construction follows.)
 func allowErrors(lconf *loader.Config) {

cmd/guru/guru_test.go

@@ -230,6 +230,7 @@ func TestGuru(t *testing.T) {
 		"testdata/src/reflection/main.go",
 		"testdata/src/what/main.go",
 		"testdata/src/whicherrs/main.go",
+		"testdata/src/softerrs/main.go",
 		// JSON:
 		// TODO(adonovan): most of these are very similar; combine them.
 		"testdata/src/calls-json/main.go",

cmd/guru/peers.go

@@ -31,7 +31,7 @@ func peers(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}

cmd/guru/pointsto.go

@@ -34,7 +34,7 @@ func pointsto(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}

cmd/guru/testdata/src/softerrs/main.go

@@ -0,0 +1,15 @@
+package main
+
+// Tests of various queries on a program containing only "soft" errors.
+// See go.tools/guru/guru_test.go for explanation.
+// See main.golden for expected query results.
+
+func _() {
+	var i int // "unused var" is a soft error
+}
+
+func f() {} // @callers softerrs-callers-f "f"
+
+func main() {
+	f() // @describe softerrs-describe-f "f"
+}

cmd/guru/testdata/src/softerrs/main.golden

@@ -0,0 +1,8 @@
+-------- @callers softerrs-callers-f --------
+softerrs.f is called from these 1 sites:
+	static function call from softerrs.main
+
+-------- @describe softerrs-describe-f --------
+reference to func f()
+defined here
+

cmd/guru/whicherrs.go

@@ -37,7 +37,7 @@ func whicherrs(q *Query) error {
 	}
 
 	// Load/parse/type-check the program.
-	lprog, err := lconf.Load()
+	lprog, err := loadWithSoftErrors(&lconf)
 	if err != nil {
 		return err
 	}