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@blkt
blkt committed Dec 23, 2024
1 parent ddccec9 commit 5e66be4
Showing 1 changed file with 112 additions and 56 deletions.
168 changes: 112 additions & 56 deletions internal/engine/eval/rego/debug.go
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Original file line number Diff line number Diff line change
Expand Up @@ -24,40 +24,25 @@ import (
"github.com/mindersec/minder/pkg/engine/v1/interfaces"
)

func MakeEventHandler(ch chan<- *debug.Event) func(debug.Event) {
func makeEventHandler(ch chan<- *debug.Event) func(debug.Event) {
return func(event debug.Event) {
ch <- &event
}
}

func MakeTracingEventHandler(ch chan<- *debug.Event) func(debug.Event) {
//goling:unused
func makeTracingEventHandler(ch chan<- *debug.Event) func(debug.Event) {

Check failure on line 34 in internal/engine/eval/rego/debug.go

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func `makeTracingEventHandler` is unused (unused)
return func(event debug.Event) {
fmt.Fprintf(os.Stderr, "%+v\n", event)
ch <- &event
}
}

func (ds *debugSession) WaitFor(
ctx context.Context,
eventTypes ...debug.EventType,
) *debug.Event {
for {
select {
case e := <-ds.ch:
if slices.Contains(eventTypes, e.Type) {
return e
}
case <-ctx.Done():
return nil
}
}
}

var (
errEmptySource = errors.New("empty source code")
errInvalidInput = errors.New("invalid input")
errInvalidInstr = errors.New("invalid instruction")
errInvalidBP = errors.New("invalid breakpoint")
errUserAbort = errors.New("user abort")
)

// Debug implements an interactive debugger for REGO-based evaluators.
Expand All @@ -67,9 +52,6 @@ func (e *Evaluator) Debug(
input *Input,
funcs ...func(*rego.Rego),
) error {
ctx, cancel := context.WithCancel(ctx)
defer cancel()

allOpts := make([]func(*rego.Rego), 0, len(e.regoOpts)+len(funcs))
allOpts = append(allOpts, e.regoOpts...)
allOpts = append(allOpts, funcs...)
Expand All @@ -80,7 +62,7 @@ func (e *Evaluator) Debug(
withInput(input),
withQuery(e.reseval.getQueryString()),
withOpts(allOpts...),
withTracingEventHandler(),
// withTracingEventHandler(),
)
if err != nil {
return fmt.Errorf("error initializing debugger: %w", err)
Expand All @@ -93,7 +75,7 @@ type debugSession struct {
prompt string
src string
lines int
input *Input
input any
query string
opts []debug.LaunchOption
ch chan *debug.Event
Expand Down Expand Up @@ -125,11 +107,7 @@ func withSource(src string) debugSessionOption {

func withInput(input any) debugSessionOption {
return func(ds *debugSession) error {
inner, ok := input.(*Input)
if !ok {
return fmt.Errorf("%w: wrong type %T", errInvalidInput, input)
}
ds.input = inner
ds.input = input
return nil
}
}
Expand Down Expand Up @@ -159,11 +137,20 @@ func withOpts(opts ...func(*rego.Rego)) debugSessionOption {
}
}

//goling:unused
func withTracingEventHandler() debugSessionOption {

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func `withTracingEventHandler` is unused (unused)
return func(ds *debugSession) error {
// NOTE: this channel must be buffered, because REGO
// interpreter emits several events that we're
// currently handling in the same thread of execition
// of the CLI interface.
//
// The solution would be handling CLI events and
// debuggee events asynchronously, but we're not there
// yet.
ch := make(chan *debug.Event, 10)
ds.ch = ch
ds.handler = MakeTracingEventHandler(ch)
ds.handler = makeTracingEventHandler(ch)
return nil
}
}
Expand All @@ -180,20 +167,62 @@ func newDebugSession(
}

if ds.handler == nil {
// NOTE: this channel must be buffered, because REGO
// interpreter emits several events that we're
// currently handling in the same thread of execition
// of the CLI interface.
//
// The solution would be handling CLI events and
// debuggee events asynchronously, but we're not there
// yet.
ch := make(chan *debug.Event, 10)
ds.ch = ch
ds.handler = MakeEventHandler(ch)
ds.handler = makeEventHandler(ch)
}

return ds, nil
}

func (ds *debugSession) waitFor(
ctx context.Context,
eventTypes ...debug.EventType,
) *debug.Event {
for {
select {
case e := <-ds.ch:
if slices.Contains(eventTypes, e.Type) {
return e
}
case <-ctx.Done():
return nil
}
}
}

func (ds *debugSession) startDebugger(
ctx context.Context,
) error {
debugger := debug.NewDebugger(
debug.SetEventHandler(ds.handler),
)
// This combination of flags provides roughly the same user
// experience as one would have while debugging imperative
// languages using a standard debugger like lldb or gdb.
//
// Specifically, `StopOnEntry` stops when entering an
// expression, which is like stepping through some, but not
// all, lines and even inside the same line multiple times in
// the case of list/set comprehensions, while `StopOnFail`
// results in stopping at all expressions producing a `false`
// value, which is similar to the previous case in that it
// stops every time a check fails during a list/set
// comprehension.
//
// The previous descriptions must be taken with a grain of
// salt and are likely missing useful cases. That said, the
// described cases are hardly seen when debugging imperative
// languages, which is the user experience we want to provide
// at the moment. Of course, this might change in the future.
launchProps := debug.LaunchEvalProperties{
LaunchProperties: debug.LaunchProperties{
StopOnEntry: false,
Expand Down Expand Up @@ -242,11 +271,11 @@ func (ds *debugSession) Start(ctx context.Context) error {
}
fmt.Fprintf(&b, "Restarted")
case line == "c":
if err := ds.session.Resume(thr); err != nil {
if err := ds.session.ResumeAll(); err != nil {
return fmt.Errorf("error resuming execution: %w", err)
}

evt := ds.WaitFor(ctx,
evt := ds.waitFor(ctx,
debug.ExceptionEventType,
debug.StoppedEventType,
debug.StdoutEventType,
Expand Down Expand Up @@ -280,6 +309,9 @@ func (ds *debugSession) Start(ctx context.Context) error {
case debug.TerminatedEventType:
fmt.Fprintf(&b, "\nTerminated\n")
}
case line == "q":
return errUserAbort

case line == "locals":
if err := printLocals(&b, ds.session, thr); err != nil {
return fmt.Errorf("error printing locals: %w", err)
Expand Down Expand Up @@ -343,11 +375,23 @@ func (ds *debugSession) Start(ctx context.Context) error {
return fmt.Errorf("error getting stack trace: %w", err)
}
if loc := getCurrentLocation(stack); loc != nil {
loc.Row += 1 // let's hope it always exists...
loc.Col = 0
// Unfortunately, getting the column
// right is tricky, since source-level
// breakpoints only look at line
// numbers in the REGO interpreter, so
// the safest assumption is starting
// from 0.
//
// It would be great if the frame
// struct contained details about the
// position in the source.
nextloc := location.Location{
Row: loc.Row + 1, // let's hope it always exists...
Col: 0,
}

// add internal breakpoint
bp, err := ds.session.AddBreakpoint(*loc)
bp, err := ds.session.AddBreakpoint(nextloc)
if err != nil {
return fmt.Errorf("error setting breakpoint: %w", err)
}
Expand All @@ -357,7 +401,7 @@ func (ds *debugSession) Start(ctx context.Context) error {
return fmt.Errorf("error resuming execution: %w", err)
}

evt := ds.WaitFor(ctx, debug.StoppedEventType)
evt := ds.waitFor(ctx, debug.StoppedEventType)
stack, err := ds.session.StackTrace(evt.Thread)
if err != nil {
return fmt.Errorf("error getting stack trace: %w", err)
Expand All @@ -374,43 +418,39 @@ func (ds *debugSession) Start(ctx context.Context) error {
case line == "s",
line == "sv":
if err := ds.session.StepOver(thr); err != nil {
panic(err)
return fmt.Errorf("error on step-over: %w", err)
}
evt := ds.WaitFor(ctx, debug.StoppedEventType)
evt := ds.waitFor(ctx, debug.StoppedEventType)
stack, err := ds.session.StackTrace(evt.Thread)
if err != nil {
return fmt.Errorf("error getting stack trace: %w", err)
}
printSource(&b, ds.src, stack)
case line == "si":
go func() {
if err := ds.session.StepIn(thr); err != nil {
panic(err)
}
}()
evt := ds.WaitFor(ctx, debug.StoppedEventType)
if err := ds.session.StepIn(thr); err != nil {
return fmt.Errorf("error on step-in: %w", err)
}
evt := ds.waitFor(ctx, debug.StoppedEventType)
stack, err := ds.session.StackTrace(evt.Thread)
if err != nil {
return fmt.Errorf("error getting stack trace: %w", err)
}
printSource(&b, ds.src, stack)
case line == "so":
go func() {
if err := ds.session.StepOut(thr); err != nil {
panic(err)
}
}()
evt := ds.WaitFor(ctx, debug.StoppedEventType)
if err := ds.session.StepOut(thr); err != nil {
return fmt.Errorf("error on step-out: %w", err)
}
evt := ds.waitFor(ctx, debug.StoppedEventType)
stack, err := ds.session.StackTrace(evt.Thread)
if err != nil {
return fmt.Errorf("error getting stack trace: %w", err)
}
printSource(&b, ds.src, stack)
case line == "q":
return fmt.Errorf("user abort")

case line == "h",
line == "help":
printHelp(&b)

case strings.HasPrefix(line, "p"):
varname, err := toVarName(line)
if err != nil {
Expand All @@ -433,6 +473,7 @@ func (ds *debugSession) Start(ctx context.Context) error {
if err := printVar(&b, r, ds.session, thr); err != nil {
return fmt.Errorf("error printing variables: %w", err)
}

case strings.HasPrefix(line, "b"):
loc, err := toLocation(line, ds.lines)
if err != nil {
Expand Down Expand Up @@ -627,10 +668,24 @@ func printSource(b *strings.Builder, src string, stack debug.StackTrace) {
for idx, line := range strings.Split(src, "\n") {
fmt.Fprintf(b, "%*d: %s", padding, idx+1, line)
if idx+1 == loc.Row {
theline := strings.Split(string(loc.Text), "\n")[0]
// `theline` is the very first line of
// the expression starting at the
// given position.
//
// In REGO expressions can span
// multiple lines (for example, rules
// do), but we really are interested
// in underlining only the first line
// of the given expression.
//
// For weird underlyining starting
// from column 0 of the line, see
// comment on setting source-level
// breakpoints.
theline := strings.Split(line, "\n")[0]
fmt.Fprintf(b, "\n%s%s",
strings.Repeat(" ", loc.Col+int(padding)+2-1),
cli.SimpleBoldStyle.Render(strings.Repeat("^", len(theline))),
strings.Repeat(" ", int(padding)+2+loc.Col-1),
cli.SimpleBoldStyle.Render(strings.Repeat("^", len(theline)-loc.Col+1)),
)
}
fmt.Fprintln(b)
Expand All @@ -654,6 +709,7 @@ func printLocals(b *strings.Builder, s debug.Session, thrID debug.ThreadID) erro
}

if len(trace) == 0 {
fmt.Fprintln(b, "No locals")
return nil
}

Expand Down

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