I've been reading up on DAP and wanted to share... > There are many areas though that are unique to Daffodil that have no representation in the spec. These things (like InputStream, Infoset, PoU, different variable types, backtracking, etc) will need an extension to DAP. This really boils down to defining these things to fit under the DAP BaseProtocol and enabling handling of those objects on both the front and back ends.
To me, much of the current state exposed by the (Daffodil) Debugger translates directly to a DAP Variable[1]. DAP Variables can be nested/hierarchical, so they could (potentially) model larger data like the infoset. I can imagine shoving all the current state into Variables as a proof-of-concept. It also seems like the processing stack maintained by the Daffodil PState, where each item references the relevant schema element, could translate to the DAP StackFrame type [2]. That is, the path from the schema root to the currently processing schema element becomes the "call stack". (Apologies if I don't have all the Daffodil terms lined up correctly.) For displaying the input data and processing progress, I looked at a few existing VS Code extensions that provided non-builtin views, some of which interact with their DAP debugger code [3] [4] [5] [6]. Finally, I took a cursory look at scala-debug-adapter [7], which, for reference, wraps Microsoft's java-debug implementation of DAP. I was curious about the set of request/response and event types. Additionally, the Typescript API to VS Code offers custom DAP requests and responses, but I couldn't find the equivalent notion in the java-debug project. .. Adam [1] https://microsoft.github.io/debug-adapter-protocol/specification#Types_Variable [2] https://microsoft.github.io/debug-adapter-protocol/specification#Types_StackFrame [3] https://github.com/scalameta/metals-vscode (provides a debugger and non-debugger custom UI) [4] https://github.com/microsoft/vscode-cpptools (debugger + memory view) [5] https://marketplace.visualstudio.com/items?itemName=marus25.cortex-debug (debugger + memory view, https://github.com/Marus/cortex-debug/blob/master/src/frontend/memory_content_provider.ts ) [6] https://marketplace.visualstudio.com/items?itemName=slevesque.vscode-hexdump (extension for hexdumps that could be controlled by other extensions) [7] https://github.com/scalacenter/scala-debug-adapter [8] https://github.com/microsoft/java-debug On Tue, Apr 20, 2021 at 7:08 AM John Wass <jwa...@gmail.com> wrote: > > Going to look deeper into how DAP might fit with Daffodil > > Have been looking over DAP and getting a good feeling about it. The > specification [1] seems general enough that it could be applied to Daffodil > and cover a swath of common operations (like start, stop, break, continue, > code locations, variables, etc). > > There are many areas though that are unique to Daffodil that have no > representation in the spec. These things (like InputStream, Infoset, PoU, > different variable types, backtracking, etc) will need an extension to > DAP. This really boils down to defining these things to fit under the DAP > BaseProtocol and enabling handling of those objects on both the front and > back ends. > > On the backend we need a Daffodil DAP protocol server. Existing JVM > implementations (like Java [2], Scala [3]) are tied closely to JDI and > would bring a lot of extra baggage to work around that. Developing a > Daffodil specific implementation is no small task, but feasible. There are > a several existing implementations on the JVM that are close and can be > looked at for reference. > > The backend implementation would look similar to what was described in an > earlier post. We could use ZIO/Akka/etc to implement the backend Protocol > Server to enable the IO between the Daffodil process and the DAP clients. > This implementation would now be guided by the DAP specification. > > With the protocol and backend extended to fit Daffodil that leaves the > frontend. In theory an existing IDE plugin should get pretty close to > being able to perform the common debug operations mentioned above. To > support the Daffodil extensions there will need to be handling of the > extended protocol into whatever views are desired/applicable. > > > Also looking into the Java Debug Interface (JDI) for comparison. > > JDI appears to be the wrong level of abstraction for what we are talking > about in debugging Daffodil for schema development. While DAP does do JVM > debugging (through a JDI DAP impl) it also generalizes to many other > debugging scenarios. JDI on the other hand is very tied to the JVM. > > Extending the JDI appears to be more complex than dealing with DAP, and > even though the JDI API is mostly defined with interfaces, there are choke > points that limit to JVM concepts. For example jdi.Value has a finite set > of JVM types that it works with, its not clear where Daffodil types would > plugin if even possible. > > The final note is that unique Daffodil features wouldn’t get to IDE support > any faster JDI. In some cases, like VS Code, you would still need an > extended DAP to support these features. > > > and depending on how it shakes out will update the example to show > integration > > It would appear wise to investigate DAP further. Next step is to refine > these thoughts with a prototype. I started an implementation in the example > debugger project [4] to try to run the current example on a _minimal_ DAP > implementation. > > > [1] https://microsoft.github.io/debug-adapter-protocol/specification > [2] https://github.com/Microsoft/java-debug > [3] https://github.com/scalacenter/scala-debug-adapter > [4] https://github.com/jw3/example-daffodil-debug > > > On Mon, Apr 12, 2021 at 9:58 AM John Wass <jwa...@gmail.com> wrote: > > > > the code is here https://github.com/jw3/example-daffodil-debug > > > > There is now a complete console based example for Zio that demonstrates > > controlling the debug flow while distributing the current state to three > > "displays". > > 1. infoset at current step > > 2. diff of infoset against previous step > > 3. bit position and value of data. > > > > These displays are very rudimentary but demonstrate the ability to > > asynchronously populate multiple views while synchronously controlling > the > > debug loop. > > > > > - The new protocol being informed by existing debugger and DAPis key > > > > Going to look deeper into how DAP might fit with Daffodil, and depending > > on how it shakes out will update the example to show integration. > > > > Some interesting links to start with > > - https://github.com/scalacenter/scala-debug-adapter > > - > > > https://scalameta.org/metals/docs/integrations/debug-adapter-protocol.html > > - https://github.com/microsoft/java-debug > > > > Also looking into the Java Debug Interface (JDI) for comparison. > > > > > > On Thu, Apr 8, 2021 at 12:36 PM John Wass <jwa...@gmail.com> wrote: > > > >> Revisiting this post after doing some debugger related work and thinking > >> about debug protocol/adapters to connect external tooling to the debug > >> process. > >> > >> This comment is good > >> > >> > This allo makes me wonder if an approach worth taking for the future > of > >> Daffodil schema debugging is developing a sort of "Daffodil Debug > >> Protocol". I imagine it would be loosely based on DAP (which is > >> essentially JSON message based) but could be targeted to the things > that a > >> DFDL schema debugger would really need. An added benefit with some > sort of > >> protocol is the debugger interface can be uncoupled from Daffodil > >> itself, so we could implement a TUI/GUI/whatever in any language/GUI > >> framework and just have it communicate the protocol over some form of > >> IPC. Another benefit is that any future backends could implement this > >> protocol and so a single debugger could hook into different backends > >> without much issue. Unfortunately, defining such a protocol might be a > >> large task, but we do have our existing debug infrastructure and things > >> like DAP to guide its development/design. > >> > >> Some thoughts on this > >> - Defining the protocol will be a large task, but a minimal version > >> should get up and round tripping quickly with a minimal subset of the > >> protocol. > >> - The new protocol being informed by existing debugger and DAPis key > >> - Uncoupling from Daffodil is key > >> - Adapt the Daffodil protocol to produce DAP after the fact so as not to > >> constrain Daffodil debugging capability > >> - We dont need to tie the protocol or adapters to a single framework, > >> implementations of the IO layer should be simple enough to support > multiple > >> things (eg Akka, Zio, "basic" ...) > >> - The current debugger lives in runtime1, but can we make an abstract > API > >> that any runtime would implement? > >> > >> Maybe a solution is structured like this > >> - daffodil-debug-api: > >> - protocol model > >> - interfaces: debugger / IO adapter / etc > >> - lives in daffodil repo (new subproject?) > >> - daffodil-debug-io-NAME > >> - provides implementation of a specific IO adapter > >> - multiple projects possible (daffodil-debugger-akka, > >> daffodil-debugger-zio, etc) > >> - supported ones live in their own subprojects, but other can be > >> plugged in from external sources > >> - ability to support multiple implementations reduces risk of lock-in > >> - debugger applications > >> - maintained in external repositories > >> - depending on the IO implementation these could execute be in > separate > >> process or on separate machine > >> - like Steve said, could be any language / framework > >> > >> Three types of reference implementations / sample applications could > also > >> guide the development of the API > >> 1. a replacement for the existing TUI debugger, expected to end up > with > >> at minimum the same functionality as the current one. > >> 2. a standalone GUI (JavaFX, Scala.js, ..) debugger > >> 3. an IDE integration > >> > >> Thoughts? > >> > >> Also I'm working on some reference implementations of these concepts > >> using Akka and Zio. Not quite ready to talk through it yet, but the > code > >> is here https://github.com/jw3/example-daffodil-debug > >> > >> > >> > >> On Wed, Jan 6, 2021 at 1:42 PM Steve Lawrence <slawre...@apache.org> > >> wrote: > >> > >>> Yep, something like that seems very reasonable for dealing with large > >>> infosets. But it still feels like we still run into usability issues. > >>> For example, what if a user wants to see more? We need some > >>> configuration options to increase what we've ellided. It's not big, but > >>> every new thing that needs configuration adds complexity and decreases > >>> usability. > >>> > >>> And I think the only reason we are trying to spend effort elliding > >>> things is because we're limited to this gdb-like interface where you > can > >>> only print out a little information at a time. > >>> > >>> I think what would really is to dump this gdb interface and instead use > >>> multiple windows/views. As a really close example to what I imagine, I > >>> recently came across this hex editor: > >>> > >>> https://www.synalysis.net/ > >>> > >>> The screenshots are a bit small so it's not super clear, but this tool > >>> has one view for the data in hex, and one view for a tree of parsed > >>> results (which is very similar to our infoset). The "infoset" view has > >>> information like offset/length/value, and can be related back to the > >>> data view to find the actual bits. > >>> > >>> I imagine the "next generation daffodil debugger" to look much like > >>> this. As data is parsed, the infoset view fills up. This view could act > >>> like a standard GUI tree so you could collapse sections or scroll > around > >>> to show just the parts you care about, and have search capabilities to > >>> quickly jump around. The advantage here is you no longer really need > >>> automated eliding or heuristics for what the user *might* care about. > >>> You just show the whole thing and let user scroll around. As daffodil > >>> parses and backtracks, this tree grows or shrinks. > >>> > >>> I also imagine you could have a cursor moving around the hex view, so > as > >>> daffodil moves around (e.g. scanning for delimiters, extracting > >>> integers), one could update this data view to show what daffodil is > >>> doing and where it is. > >>> > >>> I also image there could be other views as well. For example, a schema > >>> view to show where in the schema daffodil is, and to add/remove > >>> breakpoints. And an information view for things like variables, > in-scope > >>> delimiters, PoU's, etc. > >>> > >>> The only reason I mention a debug protcol is that would allow this GUI > >>> to be more easily written in something other that Java/Scala to take > >>> advantage of other GUI toolkits. It's been a long while since I've done > >>> anything with Java guis, but they seems pretty poor that last I looked > >>> at them. Would even allow for a TUI, which Java has little/no support > >>> for. Also enables things like remote deubgging if an socket IPC was > >>> used. Though I'm not sure all of that is necessary. Just thinking what > >>> would be ideal, and it can always be pared back. > >>> > >>> > >>> On 1/6/21 12:44 PM, Beckerle, Mike wrote: > >>> > I don't think of it as a daffodil debug protocol, but just a > >>> separation of concerns between display of information and the > behaviors of > >>> parse/unparse that need to be points where users can pause, and data > >>> structures available to display. > >>> > > >>> > E.g., it is 100% a display issue that the infoset (shown as XML) is > >>> clumsy, too big, etc. The infoset is available in the processor > state, and > >>> one can examine the current node, enclosing node, prior sibling(s), > >>> following sibling(s), etc. One can elide contents that are too big for > >>> hexBinary, etc. > >>> > > >>> > I think this problem, how to display the infoset with sensible limits > >>> on sizing, is fairly easy to come up with some design for, that will at > >>> least be (1) always fairly small (2) much more useful in more cases. It > >>> won't be perfect but can be much better than what we do now. > >>> > > >>> > One sensible display "mode" should be that displaying the context > >>> surrounding the current element (when parsing or unparsing) displays at > >>> most N-lines. (N/2 before, N/2 after) with a maximum length of L > characters > >>> (settable within reason ?) > >>> > > >>> > Sibling and enclosing nodes would be displayed eliding their contents > >>> to at most 1 line. > >>> > > >>> > Here's an example of what I mean. Displaying up to M=10 lines total: > >>> > > >>> > ... > >>> > <enclosingParent1> > >>> > ... > >>> > <priorSibling2>89ab782 ...</...> > >>> > <priorSibling1>some text is here and some more text</...> > >>> > <currentNode>value might be some big thing which needs to be > elided > >>> ...</...> > >>> > <followingSibling1> ... </...> > >>> > ??? > >>> > </enclosingParent1> > >>> > ??? > >>> > > >>> > The </...> is just an idea to reduce XML matching end-tag clutter. > >>> > > >>> > The ... on a line alone or where element content would appear > >>> generally means 1 or more other siblings. The way the display above > starts > >>> with ... means that this is a relative inner nest, not starting from > the > >>> absolute root. > >>> > > >>> > The ... within simple content means that content is elided to fit on > >>> one line. Always follows some text characters to differentiate from the > >>> child-element context. > >>> > > >>> > The ??? means zero or more other siblings. > >>> > > >>> > I used bold italic above to point out that the current node would be > >>> highlighted somehow. Probably a way to do this that doesn't require > display > >>> modes would be useful. E.g., a text marker like ">>>" as in: > >>> > > >>> >>>> <currentNode>value .... </...> > >>> > > >>> > might be better, particularly for a trace output being dumped to a > >>> text file. > >>> > > >>> > I made the above example an unparser kind of example by showing a > >>> following sibling that exists that is after the current node. > >>> > > >>> > I think the key concept is that any sibling node is displayed in a > way > >>> that fits on one line. > >>> > E.g., even if the element name was really long, I'd suggest: > >>> > > >>> > <hereIsAnElementWithASuperLongName...>abcd ... </...> > >>> > > >>> > Where the element name itself gets elided because it is too long. > >>> > > >>> > A thought. Note that the above presentation is shown as quasi-XML, > but > >>> there's nothing XML-specific about it. A JSON-friendly equivalent > could be > >>> done as well: > >>> > > >>> > enclosingParent1 = { > >>> > ... > >>> > priorSibling2 = "89ab782..." > >>> > priorSibling1 = "some text is here and some more text" > >>> > currentNode = "value might be some big thing which needs to be > >>> elided ..." > >>> > followingSibling1 = { ... } > >>> > ??? > >>> > } > >>> > > >>> > That's enough for 1 email thread on this debug topic. > >>> > > >>> > > >>> > ________________________________ > >>> > From: Steve Lawrence <slawre...@apache.org> > >>> > Sent: Tuesday, January 5, 2021 2:26 PM > >>> > To: dev@daffodil.apache.org <dev@daffodil.apache.org> > >>> > Subject: The future of the daffodil DFDL schema debugger? > >>> > > >>> > > >>> > Now that we're in a new year, I'd like to start a discussion about > the > >>> > Daffodil DFDL Schema debugger and how it might be improved to be more > >>> > useful. > >>> > > >>> > Note that this is not the capabilities to debug Daffodil itself in > >>> > something like Eclipse/IntelliJ, but the ability for Daffodil to > >>> provide > >>> > enough extra information during a parse/unparse so that a schema > >>> > developer can get an idea of what Daffodil is doing. This makes it > >>> > easier for users (rather than developers) to determine why a schema > >>> > isn't giving the expect parse/unparse result (either because of bad > >>> data > >>> > or a faulty schema. > >>> > > >>> > The current state of the debugger is enabled by providing the --debug > >>> or > >>> > --trace flags in the CLI. More information about that here: > >>> > > >>> > https://daffodil.apache.org/debugger/ > >>> > > >>> > This enables a TUI and commands somewhat similar to GDB, providing > >>> thins > >>> > like breakpoints, steps, displaying the current infoset, display a > dump > >>> > of the data, etc. > >>> > > >>> > Although I find this tool pretty useful, it definitely has some > glaring > >>> > issues. > >>> > > >>> > The most glaring to me is that it really isn't useful at all for > >>> > debugging unparse. The data dumps only include then main > outputstream, > >>> > so determine things like suspensions and buffered output is > impossible. > >>> > > >>> > Another issue is the infoset output. When outputting the infoset, the > >>> > debugger currently just walks the entire thing and converts it to XML > >>> > and displays the XML. For large infosets, this is excess and can make > >>> it > >>> > impossible to use, even with some configurations the limit how much > of > >>> > that infoset is actually printed to the screen. Also things like > large > >>> > hex binary blobs create excessive and unusable output. > >>> > > >>> > Another thing I feel is missing is a schema view. Right now it's very > >>> > difficult to know where in the schema Daffodil actually is. > >>> > > >>> > I think these issues just need some thought improvement. One could > >>> > imagine a better way to stringify our unparse buffers for debug. One > >>> > could image a way to receive infoset state changes so the debugger > can > >>> > track things like backtracks and remove infosets. One could image a > way > >>> > display the schema > >>> > > >>> > We just need a better way to stringify the current state of the > unparse > >>> > data including buffers, and we need a way to for the debugger to > >>> receive > >>> > state change information about infoset so it can update displays > rather > >>> > than just constantly printing the entire infoset. > >>> > > >>> > However, I think another other big issue is just usability in > general. > >>> I > >>> > think the CLI usage is reasonable, but it's not always user friendly, > >>> > and is difficult to view multiple things at the same time. I think > >>> > because of this very few people even use this tool. So this this like > >>> > perhaps something worth focus. > >>> > > >>> > My first thought to improving this usability issue would be to > >>> implement > >>> > the Debug Adapter Protocol (DAP) > >>> > (https://microsoft.github.io/debug-adapter-protocol/) for Daffodil, > >>> > which many IDE's implement. With this implemented, Daffodil could be > >>> > plugged in to any IDE that supports it and essentially get debugging > >>> for > >>> > free, without the need to worry about the GUI elements. > >>> > > >>> > I do have concerns that this just wouldn't have enough functionality > >>> > that we'd really need. For example, DAP really only has ability show > >>> > code (Daffodil's equivalent is the DFDL schema). There isn't a way to > >>> > show a live view of the infoset or data. Most DAP IDE's do have a > >>> > console output, so we could potentially make it so the console output > >>> is > >>> > a live view of infoset/data. But I'm not even sure most DAP friendly > >>> > IDE's could support this kindof console output. Does anyone have > >>> > familiarity with DAP IDE's or and what kinds of console capabilities > >>> are > >>> > available? > >>> > > >>> > I also looked into TUI libraries with the idea that we could just > >>> extend > >>> > our current debugger user interface to be a bit friendlier. > >>> > Unfortunately, there aren't too many Java/Scala TUI libraries and > those > >>> > that do exist don't have Apache friendly licenses. We also want to be > >>> > careful about increase dependencies just for a debugger than many > >>> people > >>> > might not use, so large graphics libraries are probably out of the > >>> question. > >>> > > >>> > This allo makes me wonder if an approach worth taking for the future > of > >>> > Daffodil schema debugging is developing a sort of "Daffodil Debug > >>> > Protocol". I imagine it would be loosely based on DAP (which is > >>> > essentially JSON message based) but could be targeted to the things > >>> that > >>> > a DFDL schema debugger would really need. An added benefit with some > >>> > sort of protocol is the debugger interface can be uncoupled from > >>> > Daffodil itself, so we could implement a TUI/GUI/whatever in any > >>> > language/GUI framework and just have it communicate the protocol over > >>> > some form of IPC. Another benefit is that any future backends could > >>> > implement this protocol and so a single debugger could hook into > >>> > different backends without much issue. Unfortunately, defining such a > >>> > protocol might be a large task, but we do have our existing debug > >>> > infrastructure and things like DAP to guide its development/design. > >>> > > >>> > Thoughts? Does such a Daffodil Debug Protocol seem worth it? Perhaps > we > >>> > really just need the few improvements mentioned to the existing > >>> > debugger. Is that enough to make it usable? Or is an entirely > different > >>> > approach needed to debugging schemas? > >>> > > >>> > >>> >
