cmd/go: make go list error behavior consistent in tests

"go list -test" constructs a package graph, then creates test packages
for the target. If it encounters an error (for example, a syntax error
in a test file or a test function with the wrong signature), it
reports the error and exits without printing the test packages or
their dependencies, even if the -e flag is given. This is a problem
for tools that operate on test files while users are editing them. For
example, autocomplete may not work while the user is typing.

With this change, a new function, load.TestPackagesAndErrors replaces
TestPackagesFor. The new function attaches errors to the returned test
packages instead of returning immediately. "go list -test" calls this
when the -e flag is set. TestPackagesFor now returns the same error as
before, but it returns non-nil packages so that "go list -test"
without -e can print partial results.

Fixes #28491

Change-Id: I141765c4574eae424d872eb9bf7dd63fdfb85efb
Reviewed-on: https://go-review.googlesource.com/c/go/+/164357
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/list/list.go

@@ -447,37 +447,34 @@ func runList(cmd *base.Command, args []string) {
 				continue
 			}
 			if len(p.TestGoFiles)+len(p.XTestGoFiles) > 0 {
-				pmain, ptest, pxtest, err := load.TestPackagesFor(p, nil)
-				if err != nil {
-					if *listE {
-						pkgs = append(pkgs, &load.Package{
-							PackagePublic: load.PackagePublic{
-								ImportPath: p.ImportPath + ".test",
-								Error:      &load.PackageError{Err: err.Error()},
-							},
-						})
-						continue
+				var pmain, ptest, pxtest *load.Package
+				var err error
+				if *listE {
+					pmain, ptest, pxtest = load.TestPackagesAndErrors(p, nil)
+				} else {
+					pmain, ptest, pxtest, err = load.TestPackagesFor(p, nil)
+					if err != nil {
+						base.Errorf("can't load test package: %s", err)
 					}
-					base.Errorf("can't load test package: %s", err)
-					continue
 				}
-				pkgs = append(pkgs, pmain)
-				if ptest != nil {
+				if pmain != nil {
+					pkgs = append(pkgs, pmain)
+					data := *pmain.Internal.TestmainGo
+					h := cache.NewHash("testmain")
+					h.Write([]byte("testmain\n"))
+					h.Write(data)
+					out, _, err := c.Put(h.Sum(), bytes.NewReader(data))
+					if err != nil {
+						base.Fatalf("%s", err)
+					}
+					pmain.GoFiles[0] = c.OutputFile(out)
+				}
+				if ptest != nil && ptest != p {
 					pkgs = append(pkgs, ptest)
 				}
 				if pxtest != nil {
 					pkgs = append(pkgs, pxtest)
 				}
-
-				data := *pmain.Internal.TestmainGo
-				h := cache.NewHash("testmain")
-				h.Write([]byte("testmain\n"))
-				h.Write(data)
-				out, _, err := c.Put(h.Sum(), bytes.NewReader(data))
-				if err != nil {
-					base.Fatalf("%s", err)
-				}
-				pmain.GoFiles[0] = c.OutputFile(out)
 			}
 		}
 	}

src/cmd/go/internal/load/pkg.go

@@ -1424,41 +1424,7 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) {
 		}
 	}
 	p.Internal.Imports = imports
-
-	deps := make(map[string]*Package)
-	var q []*Package
-	q = append(q, imports...)
-	for i := 0; i < len(q); i++ {
-		p1 := q[i]
-		path := p1.ImportPath
-		// The same import path could produce an error or not,
-		// depending on what tries to import it.
-		// Prefer to record entries with errors, so we can report them.
-		p0 := deps[path]
-		if p0 == nil || p1.Error != nil && (p0.Error == nil || len(p0.Error.ImportStack) > len(p1.Error.ImportStack)) {
-			deps[path] = p1
-			for _, p2 := range p1.Internal.Imports {
-				if deps[p2.ImportPath] != p2 {
-					q = append(q, p2)
-				}
-			}
-		}
-	}
-
-	p.Deps = make([]string, 0, len(deps))
-	for dep := range deps {
-		p.Deps = append(p.Deps, dep)
-	}
-	sort.Strings(p.Deps)
-	for _, dep := range p.Deps {
-		p1 := deps[dep]
-		if p1 == nil {
-			panic("impossible: missing entry in package cache for " + dep + " imported by " + p.ImportPath)
-		}
-		if p1.Error != nil {
-			p.DepsErrors = append(p.DepsErrors, p1.Error)
-		}
-	}
+	p.collectDeps()
 
 	// unsafe is a fake package.
 	if p.Standard && (p.ImportPath == "unsafe" || cfg.BuildContext.Compiler == "gccgo") {
@@ -1528,6 +1494,48 @@ func (p *Package) load(stk *ImportStack, bp *build.Package, err error) {
 	}
 }
 
+// collectDeps populates p.Deps and p.DepsErrors by iterating over
+// p.Internal.Imports.
+//
+// TODO(jayconrod): collectDeps iterates over transitive imports for every
+// package. We should only need to visit direct imports.
+func (p *Package) collectDeps() {
+	deps := make(map[string]*Package)
+	var q []*Package
+	q = append(q, p.Internal.Imports...)
+	for i := 0; i < len(q); i++ {
+		p1 := q[i]
+		path := p1.ImportPath
+		// The same import path could produce an error or not,
+		// depending on what tries to import it.
+		// Prefer to record entries with errors, so we can report them.
+		p0 := deps[path]
+		if p0 == nil || p1.Error != nil && (p0.Error == nil || len(p0.Error.ImportStack) > len(p1.Error.ImportStack)) {
+			deps[path] = p1
+			for _, p2 := range p1.Internal.Imports {
+				if deps[p2.ImportPath] != p2 {
+					q = append(q, p2)
+				}
+			}
+		}
+	}
+
+	p.Deps = make([]string, 0, len(deps))
+	for dep := range deps {
+		p.Deps = append(p.Deps, dep)
+	}
+	sort.Strings(p.Deps)
+	for _, dep := range p.Deps {
+		p1 := deps[dep]
+		if p1 == nil {
+			panic("impossible: missing entry in package cache for " + dep + " imported by " + p.ImportPath)
+		}
+		if p1.Error != nil {
+			p.DepsErrors = append(p.DepsErrors, p1.Error)
+		}
+	}
+}
+
 // SafeArg reports whether arg is a "safe" command-line argument,
 // meaning that when it appears in a command-line, it probably
 // doesn't have some special meaning other than its own name.

src/cmd/go/internal/load/test.go

@@ -39,10 +39,43 @@ type TestCover struct {
 	DeclVars func(*Package, ...string) map[string]*CoverVar
 }
 
-// TestPackagesFor returns three packages:
+// TestPackagesFor is like TestPackagesAndErrors but it returns
+// an error if the test packages or their dependencies have errors.
+// Only test packages without errors are returned.
+func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Package, err error) {
+	pmain, ptest, pxtest = TestPackagesAndErrors(p, cover)
+	for _, p1 := range []*Package{ptest, pxtest, pmain} {
+		if p1 == nil {
+			// pxtest may be nil
+			continue
+		}
+		if p1.Error != nil {
+			err = p1.Error
+			break
+		}
+		if len(p1.DepsErrors) > 0 {
+			perr := p1.DepsErrors[0]
+			perr.Pos = "" // show full import stack
+			err = perr
+			break
+		}
+	}
+	if pmain.Error != nil || len(pmain.DepsErrors) > 0 {
+		pmain = nil
+	}
+	if ptest.Error != nil || len(ptest.DepsErrors) > 0 {
+		ptest = nil
+	}
+	if pxtest != nil && (pxtest.Error != nil || len(pxtest.DepsErrors) > 0) {
+		pxtest = nil
+	}
+	return pmain, ptest, pxtest, err
+}
+
+// TestPackagesAndErrors returns three packages:
+//	- pmain, the package main corresponding to the test binary (running tests in ptest and pxtest).
 //	- ptest, the package p compiled with added "package p" test files.
 //	- pxtest, the result of compiling any "package p_test" (external) test files.
-//	- pmain, the package main corresponding to the test binary (running tests in ptest and pxtest).
 //
 // If the package has no "package p_test" test files, pxtest will be nil.
 // If the non-test compilation of package p can be reused
@@ -50,33 +83,30 @@ type TestCover struct {
 // package p need not be instrumented for coverage or any other reason),
 // then the returned ptest == p.
 //
+// An error is returned if the testmain source cannot be completely generated
+// (for example, due to a syntax error in a test file). No error will be
+// returned for errors loading packages, but the Error or DepsError fields
+// of the returned packages may be set.
+//
 // The caller is expected to have checked that len(p.TestGoFiles)+len(p.XTestGoFiles) > 0,
 // or else there's no point in any of this.
-func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Package, err error) {
+func TestPackagesAndErrors(p *Package, cover *TestCover) (pmain, ptest, pxtest *Package) {
+	var ptestErr, pxtestErr *PackageError
 	var imports, ximports []*Package
 	var stk ImportStack
 	stk.Push(p.ImportPath + " (test)")
 	rawTestImports := str.StringList(p.TestImports)
 	for i, path := range p.TestImports {
 		p1 := LoadImport(path, p.Dir, p, &stk, p.Internal.Build.TestImportPos[path], ResolveImport)
-		if p1.Error != nil {
-			return nil, nil, nil, p1.Error
-		}
-		if len(p1.DepsErrors) > 0 {
-			err := p1.DepsErrors[0]
-			err.Pos = "" // show full import stack
-			return nil, nil, nil, err
-		}
 		if str.Contains(p1.Deps, p.ImportPath) || p1.ImportPath == p.ImportPath {
 			// Same error that loadPackage returns (via reusePackage) in pkg.go.
 			// Can't change that code, because that code is only for loading the
 			// non-test copy of a package.
-			err := &PackageError{
+			ptestErr = &PackageError{
 				ImportStack:   testImportStack(stk[0], p1, p.ImportPath),
 				Err:           "import cycle not allowed in test",
 				IsImportCycle: true,
 			}
-			return nil, nil, nil, err
 		}
 		p.TestImports[i] = p1.ImportPath
 		imports = append(imports, p1)
@@ -87,14 +117,6 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 	rawXTestImports := str.StringList(p.XTestImports)
 	for i, path := range p.XTestImports {
 		p1 := LoadImport(path, p.Dir, p, &stk, p.Internal.Build.XTestImportPos[path], ResolveImport)
-		if p1.Error != nil {
-			return nil, nil, nil, p1.Error
-		}
-		if len(p1.DepsErrors) > 0 {
-			err := p1.DepsErrors[0]
-			err.Pos = "" // show full import stack
-			return nil, nil, nil, err
-		}
 		if p1.ImportPath == p.ImportPath {
 			pxtestNeedsPtest = true
 		} else {
@@ -108,6 +130,7 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 	if len(p.TestGoFiles) > 0 || p.Name == "main" || cover != nil && cover.Local {
 		ptest = new(Package)
 		*ptest = *p
+		ptest.Error = ptestErr
 		ptest.ForTest = p.ImportPath
 		ptest.GoFiles = nil
 		ptest.GoFiles = append(ptest.GoFiles, p.GoFiles...)
@@ -140,6 +163,7 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 			m[k] = append(m[k], v...)
 		}
 		ptest.Internal.Build.ImportPos = m
+		ptest.collectDeps()
 	} else {
 		ptest = p
 	}
@@ -155,6 +179,7 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 				GoFiles:    p.XTestGoFiles,
 				Imports:    p.XTestImports,
 				ForTest:    p.ImportPath,
+				Error:      pxtestErr,
 			},
 			Internal: PackageInternal{
 				LocalPrefix: p.Internal.LocalPrefix,
@@ -173,6 +198,7 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 		if pxtestNeedsPtest {
 			pxtest.Internal.Imports = append(pxtest.Internal.Imports, ptest)
 		}
+		pxtest.collectDeps()
 	}
 
 	// Build main package.
@@ -207,9 +233,6 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 			pmain.Internal.Imports = append(pmain.Internal.Imports, ptest)
 		} else {
 			p1 := LoadImport(dep, "", nil, &stk, nil, 0)
-			if p1.Error != nil {
-				return nil, nil, nil, p1.Error
-			}
 			pmain.Internal.Imports = append(pmain.Internal.Imports, p1)
 		}
 	}
@@ -240,8 +263,8 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 	// The list of imports is used by recompileForTest and by the loop
 	// afterward that gathers t.Cover information.
 	t, err := loadTestFuncs(ptest)
-	if err != nil {
-		return nil, nil, nil, err
+	if err != nil && pmain.Error == nil {
+		pmain.Error = &PackageError{Err: err.Error()}
 	}
 	t.Cover = cover
 	if len(ptest.GoFiles)+len(ptest.CgoFiles) > 0 {
@@ -254,6 +277,7 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 		pmain.Imports = append(pmain.Imports, pxtest.ImportPath)
 		t.ImportXtest = true
 	}
+	pmain.collectDeps()
 
 	// Sort and dedup pmain.Imports.
 	// Only matters for go list -test output.
@@ -299,12 +323,14 @@ func TestPackagesFor(p *Package, cover *TestCover) (pmain, ptest, pxtest *Packag
 	}
 
 	data, err := formatTestmain(t)
-	if err != nil {
-		return nil, nil, nil, err
+	if err != nil && pmain.Error == nil {
+		pmain.Error = &PackageError{Err: err.Error()}
+	}
+	if data != nil {
+		pmain.Internal.TestmainGo = &data
 	}
-	pmain.Internal.TestmainGo = &data
 
-	return pmain, ptest, pxtest, nil
+	return pmain, ptest, pxtest
 }
 
 func testImportStack(top string, p *Package, target string) []string {
@@ -420,21 +446,24 @@ type coverInfo struct {
 }
 
 // loadTestFuncs returns the testFuncs describing the tests that will be run.
+// The returned testFuncs is always non-nil, even if an error occurred while
+// processing test files.
 func loadTestFuncs(ptest *Package) (*testFuncs, error) {
 	t := &testFuncs{
 		Package: ptest,
 	}
+	var err error
 	for _, file := range ptest.TestGoFiles {
-		if err := t.load(filepath.Join(ptest.Dir, file), "_test", &t.ImportTest, &t.NeedTest); err != nil {
-			return nil, err
+		if lerr := t.load(filepath.Join(ptest.Dir, file), "_test", &t.ImportTest, &t.NeedTest); lerr != nil && err == nil {
+			err = lerr
 		}
 	}
 	for _, file := range ptest.XTestGoFiles {
-		if err := t.load(filepath.Join(ptest.Dir, file), "_xtest", &t.ImportXtest, &t.NeedXtest); err != nil {
-			return nil, err
+		if lerr := t.load(filepath.Join(ptest.Dir, file), "_xtest", &t.ImportXtest, &t.NeedXtest); lerr != nil && err == nil {
+			err = lerr
 		}
 	}
-	return t, nil
+	return t, err
 }
 
 // formatTestmain returns the content of the _testmain.go file for t.

src/cmd/go/testdata/script/list_test_e.txt

@@ -1,7 +1,7 @@
 env GO111MODULE=off
 
 # issue 25980: crash in go list -e -test
-go list -e -test -f '{{.Error}}' p
+go list -e -test -deps -f '{{.Error}}' p
 stdout '^p[/\\]d_test.go:2:8: cannot find package "d" in any of:'
 
 -- p/d.go --

src/cmd/go/testdata/script/list_test_err.txt

@@ -0,0 +1,124 @@
+# issue 28491: errors in test source files should not prevent
+# "go list -test" from returning useful information.
+
+# go list prints information for package, internal test,
+# external test, but not testmain package when there is a
+# syntax error in test sources.
+! go list -test -deps syntaxerr
+stdout pkgdep
+stdout testdep_a
+stdout testdep_b
+stdout ^syntaxerr$
+stdout '^syntaxerr \[syntaxerr.test\]'
+stdout '^syntaxerr_test \[syntaxerr.test\]'
+! stdout '^syntaxerr\.test'
+stderr 'expected declaration'
+
+# go list -e prints information for all test packages.
+# The syntax error is shown in the package error field.
+go list -e -test -deps -f '{{.ImportPath}} {{.Error | printf "%q"}}' syntaxerr
+stdout 'pkgdep <nil>'
+stdout 'testdep_a <nil>'
+stdout 'testdep_b <nil>'
+stdout 'syntaxerr\.test "[^"]*expected declaration'
+! stderr 'expected declaration'
+
+[short] stop
+
+# go list prints partial information with test naming error
+! go list -test -deps nameerr
+stdout pkgdep
+stdout testdep_a
+stdout testdep_b
+stderr 'wrong signature for TestBad'
+
+go list -e -test -deps -f '{{.ImportPath}} {{.Error | printf "%q"}}' nameerr
+stdout 'pkgdep <nil>'
+stdout 'testdep_a <nil>'
+stdout 'testdep_b <nil>'
+stdout 'nameerr\.test "[^"]*wrong signature for TestBad'
+! stderr 'wrong signature for TestBad'
+
+# go list prints partial information with error if test has cyclic import
+! go list -test -deps cycleerr
+stdout cycleerr
+stderr 'import cycle not allowed in test'
+
+go list -e -test -deps -f '{{.ImportPath}} {{.Error | printf "%q"}}' cycleerr
+stdout 'cycleerr <nil>'
+stdout 'testdep_a <nil>'
+stdout 'testdep_cycle <nil>'
+stdout 'cycleerr \[cycleerr.test\] "[^"]*import cycle not allowed in test'
+! stderr 'import cycle not allowed in test'
+
+-- syntaxerr/syntaxerr.go --
+package syntaxerr
+
+import _ "pkgdep"
+
+-- syntaxerr/syntaxerr_ie_test.go --
+package syntaxerr
+
+!!!syntax error
+
+-- syntaxerr/syntaxerr_xe_test.go --
+package syntaxerr_test
+
+!!!syntax error
+
+-- syntaxerr/syntaxerr_i_test.go --
+package syntaxerr
+
+import _ "testdep_a"
+
+-- syntaxerr/syntaxerr_x_test.go --
+package syntaxerr
+
+import _ "testdep_b"
+
+-- nameerr/nameerr.go --
+package nameerr
+
+import _ "pkgdep"
+
+-- nameerr/nameerr_i_test.go --
+package nameerr
+
+import (
+  _ "testdep_a"
+  "testing"
+)
+
+func TestBad(t *testing.B) {}
+
+-- nameerr/nameerr_x_test.go --
+package nameerr_test
+
+import (
+  _ "testdep_b"
+  "testing"
+)
+
+func TestBad(t *testing.B) {}
+
+-- cycleerr/cycleerr_test.go --
+package cycleerr
+
+import (
+  _ "testdep_a"
+  _ "testdep_cycle"
+)
+
+-- pkgdep/pkgdep.go --
+package pkgdep
+
+-- testdep_a/testdep_a.go --
+package testdep_a
+
+-- testdep_b/testdep_b.go --
+package testdep_b
+
+-- testdep_cycle/testdep_cycle.go --
+package testdep_cycle
+
+import _ "cycleerr"