Finished implementing try catch

ucl/ast.go

@@ -68,6 +68,7 @@ type astDot struct {
 }
 
 type astCmd struct {
+	Pos  lexer.Position
 	Name astDot   `parser:"@@"`
 	Args []astDot `parser:"@@*"`
 }

ucl/builtins.go

@@ -770,17 +770,38 @@ func ifBuiltin(ctx context.Context, args macroArgs) (object, error) {
 	return nil, errors.New("malformed if-elif-else")
 }
 
-func tryBuiltin(ctx context.Context, args macroArgs) (object, error) {
+func tryBuiltin(ctx context.Context, args macroArgs) (_ object, fnErr error) {
 	if args.nargs() < 1 {
 		return nil, errors.New("need at least 1 arguments")
 	}
 
+	var currError errObject
+	defer func() {
+		if errors.As(fnErr, &errBadUsage{}) {
+			return
+		}
+
+		if args.nargs() >= 2 && args.identIs(ctx, args.nargs()-2, "finally") {
+			var blockArgs []object = nil
+			if fnErr != nil {
+				blockArgs = []object{errObject{err: fnErr}}
+			}
+
+			_, err := args.evalBlock(ctx, args.nargs()-1, blockArgs, false)
+			if err != nil && fnErr == nil {
+				fnErr = err
+			}
+		}
+	}()
+
 	res, err := args.evalBlock(ctx, 0, nil, false)
+	args.shift(1)
 	if err == nil {
 		return res, nil
 	}
 
-	args.shift(1)
+	currError = errObject{err: err}
+
 	for args.identIs(ctx, 0, "catch") {
 		args.shift(1)
 
@@ -788,51 +809,20 @@ func tryBuiltin(ctx context.Context, args macroArgs) (object, error) {
 			return nil, errors.New("need at least 1 arguments")
 		}
 
-		res, err := args.evalBlock(ctx, 0, nil, false)
+		res, err := args.evalBlock(ctx, 0, []object{currError}, false)
 		if err == nil {
 			return res, nil
 		}
 
-		args.shift(2)
+		currError = errObject{err: err}
+		args.shift(1)
 	}
 
-	// TODO: handle uncaught error
+	if args.identIs(ctx, 0, "finally") && args.nargs() > 2 {
+		return nil, tooManyFinallyBlocksError(args.ast.Pos)
+	}
 
-	return nil, nil
-
-	/*
-		if guard, err := args.evalArg(ctx, 0); err == nil && isTruthy(guard) {
-			return args.evalBlock(ctx, 1, nil, false)
-		} else if err != nil {
-			return nil, err
-		}
-
-		args.shift(2)
-		for args.identIs(ctx, 0, "elif") {
-			args.shift(1)
-
-			if args.nargs() < 2 {
-				return nil, errors.New("need at least 2 arguments")
-			}
-
-			if guard, err := args.evalArg(ctx, 0); err == nil && isTruthy(guard) {
-				return args.evalBlock(ctx, 1, nil, false)
-			} else if err != nil {
-				return nil, err
-			}
-
-			args.shift(2)
-		}
-
-		if args.identIs(ctx, 0, "else") && args.nargs() > 1 {
-			return args.evalBlock(ctx, 1, nil, false)
-		} else if args.nargs() == 0 {
-			// no elif or else
-			return nil, nil
-		}
-
-		return nil, errors.New("malformed if-elif-else")
-	*/
+	return nil, currError.err
 }
 
 func foreachBuiltin(ctx context.Context, args macroArgs) (object, error) {

ucl/errors.go

@@ -0,0 +1,37 @@
+package ucl
+
+import (
+	"fmt"
+	"github.com/alecthomas/participle/v2/lexer"
+)
+
+var (
+	tooManyFinallyBlocksError = newBadUsage("try needs at most 1 finally")
+)
+
+type errorWithPos struct {
+	err error
+	pos lexer.Position
+}
+
+func (e errorWithPos) Error() string {
+	return fmt.Sprintf("%v:%v - %v", e.pos.Line, e.pos.Offset, e.err.Error())
+}
+
+func (e errorWithPos) Unwrap() error {
+	return e.err
+}
+
+type errBadUsage struct {
+	msg string
+}
+
+func newBadUsage(msg string) func(pos lexer.Position) error {
+	return func(pos lexer.Position) error {
+		return errorWithPos{err: errBadUsage{msg: msg}, pos: pos}
+	}
+}
+
+func (e errBadUsage) Error() string {
+	return "bad usage: " + e.msg
+}

ucl/objs.go

@@ -303,6 +303,16 @@ func (ma macroArgs) evalBlock(ctx context.Context, n int, args []object, pushSco
 	return nil, errors.New("expected an invokable arg")
 }
 
+type errObject struct{ err error }
+
+func (eo errObject) String() string {
+	return "error:" + eo.err.Error()
+}
+
+func (eo errObject) Truthy() bool {
+	return true
+}
+
 type invocationArgs struct {
 	eval   evaluator
 	inst   *Inst

ucl/testbuiltins_test.go

@@ -202,9 +202,10 @@ func TestBuiltins_If(t *testing.T) {
 
 func TestBuiltins_Try(t *testing.T) {
 	tests := []struct {
-		desc string
-		expr string
-		want string
+		desc    string
+		expr    string
+		want    string
+		wantErr string
 	}{
 		{desc: "single try - successful", expr: `
 			try {
@@ -215,7 +216,7 @@ func TestBuiltins_Try(t *testing.T) {
 			try {
 				error "bang"
 			}
-			echo "after"`, want: "after\n(nil)\n"},
+			echo "after"`, wantErr: "bang"},
 		{desc: "try with catch - successful", expr: `
 			try {
 				echo "good"
@@ -230,6 +231,149 @@ func TestBuiltins_Try(t *testing.T) {
 				echo "something happened"
 			}
 			echo "after"`, want: "something happened\nafter\n(nil)\n"},
+		{desc: "try with catch with passed in error - unsuccessful", expr: `
+			try {
+				error "bang"
+			} catch { |err|
+				echo (cat "the error was = " $err)
+			}
+			echo "after"`, want: "the error was = error:bang\nafter\n(nil)\n"},
+		{desc: "try with two catch - successful", expr: `
+			try {
+				echo "i'm good"
+			} catch {
+				echo "i'm also good"
+			} catch {
+				echo "wow, we made it here"
+			}
+			echo "after"`, want: "i'm good\nafter\n(nil)\n"},
+		{desc: "try with two catch - first unsuccessful", expr: `
+			try {
+				error "bang"
+			} catch {
+				echo "i'm also good"
+			} catch {
+				echo "wow, we made it here"
+			}
+			echo "after"`, want: "i'm also good\nafter\n(nil)\n"},
+		{desc: "try with two catch - both unsuccessful", expr: `
+			try {
+				error "bang"
+			} catch {
+				error "boom"
+			} catch {
+				echo "wow, we made it here"
+			}
+			echo "after"`, want: "wow, we made it here\nafter\n(nil)\n"},
+		{desc: "return value - single try", expr: `
+			set x (try { error "bang" })
+			$x`, wantErr: "bang"},
+		{desc: "return value - single try", expr: `
+			set x (try { error "bang" } catch { |err| $err })
+			$x`, want: "error:bang\n"},
+		{desc: "return value - try and catch - successful", expr: `
+			set x (try { error "bang" } catch { "hello" })
+			$x`, want: "hello\n"},
+		{desc: "return value - try and catch - unsuccessful", expr: `
+			set x (try { error "bang" } catch { error "boom" })
+			$x`, wantErr: "boom"},
+		{desc: "try with finally - successful", expr: `
+			try {
+				echo "all good"
+			} finally {
+				echo "always at end"
+			}
+			echo "after"`, want: "all good\nalways at end\nafter\n(nil)\n"},
+		{desc: "try with finally - unsuccessful", expr: `
+			try {
+				error "bang"
+			} finally {
+				echo "always at end"
+			}
+			echo "after"`, want: "always at end\n", wantErr: "bang"},
+		{desc: "try with catch and finally - successful", expr: `
+			try {
+				echo "all good"
+			} catch {
+				echo "was caught"
+			} finally {
+				echo "always at end"
+			}
+			echo "after"`, want: "all good\nalways at end\nafter\n(nil)\n"},
+		{desc: "try with catch and finally - unsuccessful", expr: `
+			try {
+				error "bang"
+			} catch {
+				echo "was caught"
+			} finally {
+				echo "always at end"
+			}
+			echo "after"`, want: "was caught\nalways at end\nafter\n(nil)\n"},
+		{desc: "try with catch and finally - catch unsuccessful", expr: `
+			try {
+				error "bang"
+			} catch {
+				error "boom"
+			} finally {
+				echo "always at end"
+			}
+			echo "after"`, want: "always at end\n", wantErr: "boom"},
+		{desc: "try with finally - finally result discarded", expr: `
+			set a (try {
+				"return me"
+			} finally {
+				"not met"
+			})
+			echo $a`, want: "return me\n(nil)\n"},
+		{desc: "try with finally - error discarded if try fails result discarded", expr: `
+			try {
+				error "bang"
+			} finally {
+				error "kaboom"
+			}`, wantErr: "bang"},
+		{desc: "try with finally - error not discarded if try succeeds", expr: `
+			try {
+				echo "all good"
+			} finally {
+				error "kaboom"
+			}`, want: "all good\n", wantErr: "kaboom"},
+		{desc: "try with finally with error - successful", expr: `
+			try {
+				echo "all good"
+			} finally { |err|
+				echo (cat "the error was " $err)
+				if (eq $err ()) { echo "that's nil" }
+			}
+			echo "after"`, want: "all good\nthe error was \nthat's nil\nafter\n(nil)\n"},
+		{desc: "try with finally - unsuccessful", expr: `
+			try {
+				error "bang"
+			} finally { |err|
+				echo (cat "the error was " $err)
+			}
+			echo "after"`, want: "the error was error:bang\n", wantErr: "bang"},
+		{desc: "try with too many finallies - unsuccessful", expr: `
+			try {
+				error "bang"
+			} finally {
+				echo "and do this"
+			} finally { |err|
+				echo (cat "the error was " $err)
+			}
+			echo "after"`, wantErr: "2:4 - bad usage: try needs at most 1 finally"},
+		{desc: "try with finally in catch - unsuccessful", expr: `
+			try {
+				try {
+					error "bang"
+				} finally { |err|
+					echo (cat "the error was " $err)
+				}
+			} catch {
+				echo "outer caught"
+			} finally {
+				echo "outer"
+			}
+			echo "after"`, want: "the error was error:bang\nouter caught\nouter\nafter\n(nil)\n"},
 	}
 
 	for _, tt := range tests {
@@ -240,7 +384,12 @@ func TestBuiltins_Try(t *testing.T) {
 			inst := New(WithOut(outW), WithTestBuiltin())
 			err := EvalAndDisplay(ctx, inst, tt.expr)
 
-			assert.NoError(t, err)
+			if tt.wantErr != "" {
+				assert.Error(t, err)
+				assert.Equal(t, tt.wantErr, err.Error())
+			} else {
+				assert.NoError(t, err)
+			}
 			assert.Equal(t, tt.want, outW.String())
 		})
 	}