interp: avoid the last panics which can be triggered by users

That is, panics due to unsupported features,
rather than bugs in our Go code.
Add tests as well.

Fixes #1305.

Author: mvdan

interp/builtin.go

@@ -791,7 +791,7 @@ func (r *Runner) builtin(ctx context.Context, pos syntax.Pos, name string, args
 			case "-o":
 				posixOpts = true
 			case "-p", "-q":
-				panic(fmt.Sprintf("unhandled shopt flag: %s", flag))
+				return failf(2, "shopt: unsupported option %q\n", flag)
 			default:
 				return failf(2, "shopt: invalid option %q\n", flag)
 			}
@@ -988,7 +988,7 @@ func (r *Runner) builtin(ctx context.Context, pos syntax.Pos, name string, args
 		r.setVar(arrayName, vr)
 
 	default:
-		return failf(2, "%s: unimplemented builtin\n", name)
+		return failf(2, "%s: unsupported builtin\n", name)
 	}
 	return exit
 }

interp/interp_test.go

@@ -1960,6 +1960,15 @@ var runTests = []runTest{
 		"mkdir d; [ -r d ] && echo r; [ -w d ] && echo w; [ -x d ] && echo x",
 		"r\nw\nx\n",
 	},
+	{
+		"test -N a",
+		"unsupported unary test op: -N\nexit status 1 #IGNORE",
+	},
+	{
+		"test -? a",
+		// TODO: this error message should refer to `-?`
+		"1:1: not a valid test operator: `a`\n1:1: a must be followed by a word\nexit status 2 #JUSTERR",
+	},
 	{
 		"[ -s a ] && echo x; echo body >a; [ -s a ] && echo y",
 		"y\n",
@@ -2499,6 +2508,14 @@ done <<< 2`,
 		"touch a ab abB Ac Ad; shopt -s nocaseglob; echo *b",
 		"ab abB\n",
 	},
+	{
+		"shopt -p",
+		"shopt: unsupported option \"-p\"\nexit status 2 #IGNORE",
+	},
+	{
+		"shopt -q",
+		"shopt: unsupported option \"-q\"\nexit status 2 #IGNORE",
+	},
 
 	// IFS
 	{`echo -n "$IFS"`, " \t\n"},

interp/os_notunix.go

@@ -47,7 +47,8 @@ func (r *Runner) access(ctx context.Context, path string, mode uint32) error {
 // doesn't have the concept of a file owner, just ACLs, and it's unclear how
 // to map the one to the other.
 func (r *Runner) unTestOwnOrGrp(ctx context.Context, op syntax.UnTestOperator, x string) bool {
-	panic(fmt.Sprintf("unhandled unary test op: %v", op))
+	r.errf("unsupported unary test op: %v\n", op)
+	return false
 }
 
 // waitStatus is a no-op on plan9 and windows.

interp/runner.go

@@ -143,7 +143,8 @@ func (r *Runner) fillExpandConfig(ctx context.Context) {
 						os.Remove(path)
 					}()
 				default:
-					panic(fmt.Sprintf("unsupported process substitution operator: %q", ps.Op))
+					// Should only happen if we forgot a case above.
+					panic(fmt.Sprintf("unexpected process substitution operator: %q", ps.Op))
 				}
 				r2.stmts(ctx, ps.Stmts)
 				r2.exit.exiting = false // subshells don't exit the parent shell
@@ -811,6 +812,7 @@ func (r *Runner) cmd(ctx context.Context, cm syntax.Command) {
 		r.outf(format, "user", elapsedString(0, cm.PosixFormat))
 		r.outf(format, "sys", elapsedString(0, cm.PosixFormat))
 	default:
+		// Should only happen if we forgot a case above.
 		r.errf("unhandled command node: %T\n", cm)
 		r.exit.code = 1
 	}

interp/test.go

@@ -119,7 +119,8 @@ func (r *Runner) binTest(ctx context.Context, op syntax.BinTestOperator, x, y st
 	case syntax.TsAfter:
 		return x > y
 	default:
-		panic(fmt.Sprintf("unsupported binary test operator: %q", op))
+		// Should only happen if we forgot a case above.
+		panic(fmt.Sprintf("unexpected binary test operator: %q", op))
 	}
 }
 
@@ -164,9 +165,9 @@ func (r *Runner) unTest(ctx context.Context, op syntax.UnTestOperator, x string)
 		return r.statMode(ctx, x, os.ModeSetuid)
 	case syntax.TsGIDSet:
 		return r.statMode(ctx, x, os.ModeSetgid)
-	// case syntax.TsGrpOwn:
-	// case syntax.TsUsrOwn:
-	// case syntax.TsModif:
+	case syntax.TsModif:
+		r.errf("unsupported unary test op: %v\n", op)
+		return false
 	case syntax.TsRead:
 		return r.access(ctx, r.absPath(x), access_R_OK) == nil
 	case syntax.TsWrite:
@@ -212,6 +213,7 @@ func (r *Runner) unTest(ctx context.Context, op syntax.UnTestOperator, x string)
 	case syntax.TsUsrOwn, syntax.TsGrpOwn:
 		return r.unTestOwnOrGrp(ctx, op, x)
 	default:
-		panic(fmt.Sprintf("unhandled unary test op: %v", op))
+		// Should only happen if we forgot a case above.
+		panic(fmt.Sprintf("unexpected unary test op: %v", op))
 	}
 }

interp/vars.go

@@ -417,7 +417,8 @@ func (r *Runner) assignVal(name string, prev expand.Variable, as *syntax.Assign,
 	case expand.Associative:
 		// TODO
 	default:
-		panic(fmt.Sprintf("unhandled conversion of kind %d", prev.Kind))
+		// Should only happen if we forgot a case above.
+		panic(fmt.Sprintf("unexpected conversion of kind %d", prev.Kind))
 	}
 	return name, prev
 }