Display variable value in tooltip on hover.

This requires a functioning language server, e.g. `verible-verilog-ls`.

example/design.v

@@ -1,22 +1,26 @@
-module counter(...);
+module counter(
+  input clk,
+  output reg [31:0] cnt = 0
+);
+
+  parameter integer LIMIT = 0;
 
-  input clk;
-  output reg [7:0] cnt = 0;
   always @(posedge clk)
-    if (cnt < 13)
-      cnt <= cnt + 1;
-    else
+    if (cnt == LIMIT)
       cnt <= 0;
+    else
+      cnt <= cnt + 1;
 
 endmodule
 
 (* top *)
-module top(...);
+module top(
+  input clk,
+  output [7:0] data,
+  output [31:0] timer
+);
 
-  input clk;
-  output [7:0] data;
-
-  reg [7:0] message [0:13];
+  reg [7:0] message [14];
   initial begin
     message[0] = "h";
     message[1] = "e";
@@ -33,12 +37,21 @@ module top(...);
     message[12] = "\n";
   end
 
-  wire [7:0] index;
-  counter counter_inst(
+  wire [7:0] message_index;
+  counter #(
+    .LIMIT(13)
+  ) counter_message(
     .clk(clk),
-    .cnt(index)
+    .cnt(message_index)
   );
 
-  assign data = message[index];
+  assign data = message[message_index];
+
+  counter #(
+    .LIMIT(32'hffffffff)
+  ) counter_timer(
+    .clk(clk),
+    .cnt(timer),
+  );
 
 endmodule

src/debug/observer.ts

@@ -1,7 +1,6 @@
 import * as vscode from 'vscode';
 
 import { UnboundReference, Designation, Reference } from '../model/sample';
-import { TimeInterval } from '../model/time';
 import { Session } from './session';
 
 class Observable<T> {
@@ -87,9 +86,8 @@ export class Observer {
                 }
                 this.reference = this.session.bindReference(this.referenceName, unboundReference);
             }
-            const interval = new TimeInterval(this.session.timeCursor, this.session.timeCursor);
-            const reference = this.reference; // could get invalidated in the meantime
-            const [sample] = await this.session.queryInterval(interval, reference);
+            const reference = this.reference; // could get invalidated during `await` below
+            const sample = await this.session.queryAtCursor(reference);
             for (const [designation, handle] of reference.allHandles()) {
                 const observable = this.observables.get(designation.canonicalKey)!;
                 observable.update(sample.extract(handle));

src/debug/session.ts

@@ -7,10 +7,23 @@ import { TimeInterval, TimePoint } from '../model/time';
 import { Reference, Sample, UnboundReference } from '../model/sample';
 import { Variable } from '../model/variable';
 import { Scope } from '../model/scope';
+import { Location } from '../model/source';
 
 function lazy<T>(thunk: () => Thenable<T>): Thenable<T> {
     return { then: (onfulfilled, onrejected) => thunk().then(onfulfilled, onrejected) };
 }
+function matchLocation(location: Location, filename: string, position: vscode.Position) {
+    if (location.file !== filename) {
+        return false;
+    }
+    if (location.startLine !== position.line) {
+        return false;
+    }
+    if (location.startColumn !== undefined && location.startColumn !== position.character) {
+        return false;
+    }
+    return true;
+}
 
 export interface ISimulationStatus {
     status: 'running' | 'paused' | 'finished';
@@ -35,10 +48,6 @@ export class Session {
         this.connection.dispose();
     }
 
-    get connection2(): Connection {
-        return this.connection;
-    }
-
     // ======================================== Inspecting the design
 
     private itemCache: Map<string, proto.ItemDescriptionMap> = new Map();
@@ -145,6 +154,27 @@ export class Session {
         }
     }
 
+    async getVariablesForLocation(filename: string, position: vscode.Position): Promise<Variable[]> {
+        const variables: Variable[] = [];
+        const extractVariablesForLocationFromScope = async (scope: string) => {
+            const items = await this.listItemsInScope(scope);
+            for (const [itemName, itemDesc] of Object.entries(items)) {
+                const itemLocation = Location.fromCXXRTL(itemDesc.src);
+                console.log(itemLocation, filename, position, itemLocation !== null && matchLocation(itemLocation, filename, position));
+                if (itemLocation !== null && matchLocation(itemLocation, filename, position)) {
+                    variables.push(Variable.fromCXXRTL(itemName, itemDesc));
+                }
+            }
+            const subScopes = await this.listScopesInScope(scope);
+            for (const subScopeName of Object.keys(subScopes)) {
+                await extractVariablesForLocationFromScope(subScopeName);
+            }
+            return null;
+        };
+        await extractVariablesForLocationFromScope('');
+        return variables;
+    }
+
     // ======================================== Querying the database
 
     private referenceEpochs: Map<string, number> = new Map();
@@ -184,8 +214,8 @@ export class Session {
     }
 
     async queryInterval(
-        interval: TimeInterval,
         reference: Reference,
+        interval: TimeInterval,
         options: { collapse?: boolean } = {}
     ): Promise<Sample[]> {
         this.checkReferenceEpoch(reference.name, reference.epoch);
@@ -213,6 +243,12 @@ export class Session {
         });
     }
 
+    async queryAtCursor(reference: Reference): Promise<Sample> {
+        const interval = new TimeInterval(this.timeCursor, this.timeCursor);
+        const [sample] = await this.queryInterval(reference, interval);
+        return sample;
+    }
+
     // ======================================== Manipulating the simulation
 
     private simulationStatusTimeout: NodeJS.Timeout | null = null;

src/debugger.ts

@@ -1,5 +1,6 @@
 import * as net from 'net';
 import * as vscode from 'vscode';
+
 import { NodeStreamLink } from './cxxrtl/link';
 import { StatusBarItem } from './ui/status';
 import { Session } from './debug/session';

src/extension.ts

@@ -1,8 +1,10 @@
 import * as vscode from 'vscode';
+
 import { CXXRTLDebugger } from './debugger';
 import * as sidebar from './ui/sidebar';
 import { globalWatchList } from './debug/watch';
 import { globalVariableOptions } from './debug/options';
+import { HoverProvider } from './ui/hover';
 import { inputTime } from './ui/input';
 
 export function activate(context: vscode.ExtensionContext) {
@@ -14,6 +16,11 @@ export function activate(context: vscode.ExtensionContext) {
     });
     context.subscriptions.push(sidebarTreeView);
 
+    const hoverProvider = new HoverProvider(rtlDebugger);
+    for (const language of HoverProvider.SUPPORTED_LANGUAGES) {
+        context.subscriptions.push(vscode.languages.registerHoverProvider(language, hoverProvider));
+    }
+
     vscode.commands.executeCommand('setContext', 'rtlDebugger.sessionStatus', rtlDebugger.sessionStatus);
     context.subscriptions.push(rtlDebugger.onDidChangeSessionStatus((state) =>
         vscode.commands.executeCommand('setContext', 'rtlDebugger.sessionStatus', state)));

src/model/styling.ts

@@ -9,6 +9,10 @@ export enum DisplayStyle {
     VHDL = 'VHDL',
 }
 
+export function languageForDisplayStyle(style: DisplayStyle): string {
+    return style as string;
+}
+
 export function variableDescription(style: DisplayStyle, variable: Variable, { scalar = false } = {}): string {
     let result = '';
     if (variable instanceof ScalarVariable && variable.lsbAt === 0 && variable.width === 1) {

src/ui/hover.ts

@@ -0,0 +1,63 @@
+import * as vscode from 'vscode';
+
+import { CXXRTLDebugger } from '../debugger';
+import { UnboundReference } from '../model/sample';
+import { ScalarVariable, Variable } from '../model/variable';
+import { DisplayStyle, languageForDisplayStyle, variableDescription, variableValue } from '../model/styling';
+import { Session } from '../debug/session';
+
+export class HoverProvider implements vscode.HoverProvider {
+    static readonly SUPPORTED_LANGUAGES: string[] = ['verilog'];
+
+    constructor(
+        private rtlDebugger: CXXRTLDebugger
+    ) {}
+
+    private async hoverForVariables(session: Session, variables: Variable[]): Promise<vscode.Hover | null> {
+        if (variables.length === 0) {
+            return null;
+        }
+        const displayStyle = vscode.workspace.getConfiguration('rtlDebugger').get('displayStyle') as DisplayStyle;
+        const hoverText = new vscode.MarkdownString();
+        const unboundReference = new UnboundReference();
+        for (const variable of variables) {
+            if (variable instanceof ScalarVariable) {
+                unboundReference.add(variable.designation());
+            }
+        }
+        const reference = session.bindReference('hover', unboundReference);
+        const sample = await session.queryAtCursor(reference);
+        for (const [designation, handle] of reference.allHandles()) {
+            const variable = designation.variable;
+            const descriptionText = variableDescription(displayStyle, variable);
+            const valueText = variableValue(displayStyle, variable, sample.extract(handle));
+            hoverText.appendCodeblock(
+                `${variable.fullName.join('.')}${descriptionText} = ${valueText}`,
+                languageForDisplayStyle(displayStyle)
+            );
+        }
+        return new vscode.Hover(hoverText);
+    }
+
+    async provideHover(document: vscode.TextDocument, position: vscode.Position, token: vscode.CancellationToken): Promise<vscode.Hover | null> {
+        const session = this.rtlDebugger.session;
+        if (session !== null) {
+            const definitions = await (
+                vscode.commands.executeCommand('vscode.executeDefinitionProvider', document.uri, position) as
+                vscode.ProviderResult<vscode.Definition | vscode.LocationLink[]>
+            );
+            let definition: vscode.Location | undefined;
+            if (definitions instanceof vscode.Location) {
+                definition = definitions;
+            } else if (definitions instanceof Array && definitions.length === 1 && definitions[0] instanceof vscode.Location) {
+                definition = definitions[0];
+            } else {
+                console.warn('vscode.executeDefinitionProvider did not return a single Location: ', definition);
+                return null;
+            }
+            const variables = await session.getVariablesForLocation(definition.uri.fsPath, definition.range.start);
+            return await this.hoverForVariables(session, variables);
+        }
+        return null;
+    }
+}