[wasm-ep] Use DOTNET_DiagnosticPorts to configure Diagnostic Server (#73370)

* [wasm-ep] Use DOTNET_DiagnosticPorts to configure Diagnostic Server

Parse it the same way that the C code does:

```
   <uri>[,<connect|listen>][,<suspend|nosuspend>]
```

- uri should be a websocket uri
- listen is not supported as it doesn't make sense with a WebSocket
- connect is the default if omitted
- suspend is the default if omitted

---

Additionally, move `mono_wasm_diagnostics_init` to later in the
startup flow.  This gives Blazor a chance to set
DOTNET_DiagnosticPorts from their `onRuntimeInitialized` callback.

Fixes https://github.com/dotnet/runtime/issues/73011

* Initialize diagnostic server in different places for Blazor and non-Blazor

It has to be after environment variables are set, but before
mono_wasm_load_runtime is called.

There is no good place that's common to both startup paths. Try it on
both.  Use a flag to make diagnostics initialization run at most
once

* update browser-eventpipe sample to use DOTNET_DiagnosticPorts

* remove unused imports

6 files changed, 128 insertions, 25 deletions

diff --git a/src/mono/sample/wasm/browser-eventpipe/Wasm.Browser.EventPipe.Sample.csproj b/src/mono/sample/wasm/browser-eventpipe/Wasm.Browser.EventPipe.Sample.csproj
index f3feef21cce..eb58b28f8cf 100644
--- a/src/mono/sample/wasm/browser-eventpipe/Wasm.Browser.EventPipe.Sample.csproj
+++ b/src/mono/sample/wasm/browser-eventpipe/Wasm.Browser.EventPipe.Sample.csproj
@@ -20,25 +20,19 @@
   <ItemGroup>
     <WasmExtraFilesToDeploy Include="index.html" />
     <WasmExtraFilesToDeploy Include="mock.js" Condition="'$(MonoDiagnosticsMock)' == 'true'"/>
-    <WasmExtraConfig Condition="true" Include="environmentVariables" Value='
-{
-  "MONO_LOG_LEVEL": "warning",
-  "MONO_LOG_MASK": "all"
-}' />
     <!-- this option requires running dotnet-dsrouter and a real dotnet-trace client -->
-    <WasmExtraConfig Condition="true and '$(MonoDiagnosticsMock)' != 'true'" Include="diagnosticOptions" Value='
+    <WasmExtraConfig Condition="'$(MonoDiagnosticsMock)' != 'true'" Include="environmentVariables" Value='
 {
-  "server": { "suspend": true, "connectUrl": "ws://localhost:8088/diagnostics" }
+  "MONO_LOG_LEVEL": "warning",
+  "MONO_LOG_MASK": "all",
+  "DOTNET_DiagnosticPorts": "ws://localhost:8088/diagnostics,suspend"
 }' />
     <!-- this option requires compiling the runtime with /p:MonoDiagnosticsMock=true and also building this project with the same property-->
-    <WasmExtraConfig Condition="true and '$(MonoDiagnosticsMock)' == 'true'" Include="diagnosticOptions" Value='
+    <WasmExtraConfig Condition="'$(MonoDiagnosticsMock)' == 'true'" Include="environmentVariables" Value='
 {
-  "server": { "suspend": false, "connectUrl": "mock:./mock.js" }
-}' />
-    <!-- this option will create an EventPipe session at startup, that will dump its data into the Emscripten VFS -->
-    <WasmExtraConfig Condition="false" Include="diagnosticOptions" Value='
-{
-  "sessions": [ { "collectRundownEvents": "true", "providers": "WasmHello::5:EventCounterIntervalSec=1" } ]
+  "MONO_LOG_LEVEL": "warning",
+  "MONO_LOG_MASK": "all",
+  "DOTNET_DiagnosticPorts": "mock:./mock.js,suspend"
 }' />
   </ItemGroup>
 
diff --git a/src/mono/wasm/runtime/cwraps.ts b/src/mono/wasm/runtime/cwraps.ts
index ccc2e72d23f..d65947d498c 100644
--- a/src/mono/wasm/runtime/cwraps.ts
+++ b/src/mono/wasm/runtime/cwraps.ts
@@ -81,6 +81,7 @@ const fn_signatures: SigLine[] = [
 
     //INTERNAL
     [false, "mono_wasm_exit", "void", ["number"]],
+    [true, "mono_wasm_getenv", "number", ["string"]],
     [true, "mono_wasm_set_main_args", "void", ["number", "number"]],
     [false, "mono_wasm_enable_on_demand_gc", "void", ["number"]],
     [false, "mono_profiler_init_aot", "void", ["number"]],
@@ -189,6 +190,7 @@ export interface t_Cwraps {
 
     //INTERNAL
     mono_wasm_exit(exit_code: number): number;
+    mono_wasm_getenv(name: string): CharPtr;
     mono_wasm_enable_on_demand_gc(enable: number): void;
     mono_wasm_set_main_args(argc: number, argv: VoidPtr): void;
     mono_profiler_init_aot(desc: string): void;
@@ -232,4 +234,4 @@ export function init_c_exports(): void {
             wf[name] = fce;
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/mono/wasm/runtime/diagnostics/index.ts b/src/mono/wasm/runtime/diagnostics/index.ts
index 20300048931..68f79ed9f01 100644
--- a/src/mono/wasm/runtime/diagnostics/index.ts
+++ b/src/mono/wasm/runtime/diagnostics/index.ts
@@ -94,12 +94,25 @@ export const diagnostics: Diagnostics = getDiagnostics();
 let suspendOnStartup = false;
 let diagnosticsServerEnabled = false;
 
-export async function mono_wasm_init_diagnostics(options: DiagnosticOptions): Promise<void> {
+let diagnosticsInitialized = false;
+
+export async function mono_wasm_init_diagnostics(opts: "env" | DiagnosticOptions): Promise<void> {
+    if (diagnosticsInitialized)
+        return;
     if (!monoWasmThreads) {
-        console.warn("MONO_WASM: ignoring diagnostics options because this runtime does not support diagnostics", options);
+        console.warn("MONO_WASM: ignoring diagnostics options because this runtime does not support diagnostics", opts);
         return;
     } else {
-        if (!is_nullish(options.server)) {
+        let options: DiagnosticOptions | null;
+        if (opts === "env") {
+            options = diagnostic_options_from_environment();
+            if (!options)
+                return;
+        } else {
+            options = opts;
+        }
+        diagnosticsInitialized = true;
+        if (!is_nullish(options?.server)) {
             if (options.server.connectUrl === undefined || typeof (options.server.connectUrl) !== "string") {
                 throw new Error("server.connectUrl must be a string");
             }
@@ -130,6 +143,74 @@ function boolsyOption(x: string | boolean): boolean {
     throw new Error(`invalid option: "${x}", should be true, false, or "true" or "false"`);
 }
 
+/// Parse environment variables for diagnostics configuration
+///
+/// The environment variables are:
+///  * DOTNET_DiagnosticPorts
+///
+function diagnostic_options_from_environment(): DiagnosticOptions | null {
+    const val = memory.getEnv("DOTNET_DiagnosticPorts");
+    if (is_nullish(val))
+        return null;
+    // TODO: consider also parsing the DOTNET_EnableEventPipe and DOTNET_EventPipeOutputPath, DOTNET_EvnetPipeConfig variables
+    // to configure the startup sessions that will dump output to the VFS.
+    return diagnostic_options_from_ports_spec(val);
+}
+
+/// Parse a DOTNET_DiagnosticPorts string and return a DiagnosticOptions object.
+/// See https://docs.microsoft.com/en-us/dotnet/core/diagnostics/diagnostic-port#configure-additional-diagnostic-ports
+function diagnostic_options_from_ports_spec(val: string): DiagnosticOptions | null {
+    if (val === "")
+        return null;
+    const ports = val.split(";");
+    if (ports.length === 0)
+        return null;
+    if (ports.length !== 1) {
+        console.warn("MONO_WASM: multiple diagnostic ports specified, only the last one will be used");
+    }
+    const portSpec = ports[ports.length - 1];
+    const components = portSpec.split(",");
+    if (components.length < 1 || components.length > 3) {
+        console.warn("MONO_WASM: invalid diagnostic port specification, should be of the form <port>[,<connect>],[<nosuspend|suspend>]");
+        return null;
+    }
+    const uri: string = components[0];
+    let connect = true;
+    let suspend = true;
+    // the C Diagnostic Server goes through these parts in reverse, do the same here.
+    for (let i = components.length - 1; i >= 1; i--) {
+        const component = components[i];
+        switch (component.toLowerCase()) {
+            case "nosuspend":
+                suspend = false;
+                break;
+            case "suspend":
+                suspend = true;
+                break;
+            case "listen":
+                connect = false;
+                break;
+            case "connect":
+                connect = true;
+                break;
+            default:
+                console.warn(`MONO_WASM: invalid diagnostic port specification component: ${component}`);
+                break;
+        }
+    }
+    if (!connect) {
+        console.warn("MONO_WASM: this runtime does not support listening on a diagnostic port; no diagnostic server started");
+        return null;
+    }
+    return {
+        server: {
+            connectUrl: uri,
+            suspend: suspend,
+        }
+    };
+
+}
+
 export function mono_wasm_diagnostic_server_on_runtime_server_init(out_options: VoidPtr): void {
     if (diagnosticsServerEnabled) {
         /* called on the main thread when the runtime is sufficiently initialized */
diff --git a/src/mono/wasm/runtime/driver.c b/src/mono/wasm/runtime/driver.c
index a4108177548..0ddc467ae59 100644
--- a/src/mono/wasm/runtime/driver.c
+++ b/src/mono/wasm/runtime/driver.c
@@ -281,6 +281,12 @@ mono_wasm_setenv (const char *name, const char *value)
 	monoeg_g_setenv (strdup (name), strdup (value), 1);
 }
 
+EMSCRIPTEN_KEEPALIVE char *
+mono_wasm_getenv (const char *name)
+{
+	return monoeg_g_getenv (name); // JS must free
+}
+
 static void *sysglobal_native_handle;
 
 static void*
diff --git a/src/mono/wasm/runtime/memory.ts b/src/mono/wasm/runtime/memory.ts
index 95373c22fb7..2ac62de35f7 100644
--- a/src/mono/wasm/runtime/memory.ts
+++ b/src/mono/wasm/runtime/memory.ts
@@ -1,7 +1,7 @@
 import monoWasmThreads from "consts:monoWasmThreads";
 import { Module, runtimeHelpers } from "./imports";
 import { mono_assert, MemOffset, NumberOrPointer } from "./types";
-import { VoidPtr } from "./types/emscripten";
+import { VoidPtr, CharPtr } from "./types/emscripten";
 import * as cuint64 from "./cuint64";
 import cwraps, { I52Error } from "./cwraps";
 
@@ -263,6 +263,18 @@ export function mono_wasm_load_bytes_into_heap(bytes: Uint8Array): VoidPtr {
     return memoryOffset;
 }
 
+export function getEnv(name: string): string | null {
+    let charPtr: CharPtr = <any>0;
+    try {
+        charPtr = cwraps.mono_wasm_getenv(name);
+        if (<any>charPtr === 0)
+            return null;
+        else return Module.UTF8ToString(charPtr);
+    } finally {
+        if (charPtr) Module._free(<any>charPtr);
+    }
+}
+
 const BuiltinAtomics = globalThis.Atomics;
 
 export const Atomics = monoWasmThreads ? {
@@ -276,4 +288,4 @@ export const Atomics = monoWasmThreads ? {
 } : {
     storeI32: setI32,
     notifyI32: () => { /*empty*/ }
-};
\ No newline at end of file
+};
diff --git a/src/mono/wasm/runtime/startup.ts b/src/mono/wasm/runtime/startup.ts
index b6e6f688030..051c0a796c5 100644
--- a/src/mono/wasm/runtime/startup.ts
+++ b/src/mono/wasm/runtime/startup.ts
@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+import MonoWasmThreads from "consts:monoWasmThreads";
 import { mono_assert, CharPtrNull, DotnetModule, MonoConfig, MonoConfigError, LoadingResource, AssetEntry, ResourceRequest } from "./types";
 import { ENVIRONMENT_IS_NODE, ENVIRONMENT_IS_SHELL, INTERNAL, Module, runtimeHelpers } from "./imports";
 import cwraps, { init_c_exports } from "./cwraps";
@@ -25,6 +26,7 @@ import { cwraps_internal } from "./exports-internal";
 import { cwraps_binding_api, cwraps_mono_api } from "./net6-legacy/exports-legacy";
 import { DotnetPublicAPI } from "./export-types";
 import { BINDING, MONO } from "./net6-legacy/imports";
+import { mono_wasm_init_diagnostics } from "./diagnostics";
 
 let all_assets_loaded_in_memory: Promise<void> | null = null;
 const loaded_files: { url: string, file: string }[] = [];
@@ -130,8 +132,8 @@ function preInit(isCustomStartup: boolean, userPreInit: (() => void)[]) {
         abort_startup(err, true);
         throw err;
     }
-    // this will start immediately but return on first await. 
-    // It will block our `preRun` by afterPreInit promise 
+    // this will start immediately but return on first await.
+    // It will block our `preRun` by afterPreInit promise
     // It will block emscripten `userOnRuntimeInitialized` by pending addRunDependency("mono_pre_init")
     (async () => {
         try {
@@ -196,7 +198,7 @@ async function onRuntimeInitializedAsync(isCustomStartup: boolean, userOnRuntime
             _print_error("MONO_WASM: user callback onRuntimeInitialized() failed", err);
             throw err;
         }
-        // finish 
+        // finish
         await mono_wasm_after_user_runtime_initialized();
     } catch (err) {
         _print_error("MONO_WASM: onRuntimeInitializedAsync() failed", err);
@@ -326,6 +328,10 @@ async function mono_wasm_after_user_runtime_initialized(): Promise<void> {
                 }
             }
         }
+        // for Blazor, init diagnostics after their "onRuntimeInitalized" sets env variables, but before their postRun callback (which calls mono_wasm_load_runtime)
+        if (MonoWasmThreads) {
+            await mono_wasm_init_diagnostics("env");
+        }
 
         if (runtimeHelpers.diagnosticTracing) console.debug("MONO_WASM: Initializing mono runtime");
 
@@ -532,8 +538,10 @@ async function _apply_configuration_from_args() {
 
     if (config.coverageProfilerOptions)
         mono_wasm_init_coverage_profiler(config.coverageProfilerOptions);
-
-    // FIXME await mono_wasm_init_diagnostics(config.diagnosticOptions);
+    // for non-Blazor, init diagnostics after environment variables are set
+    if (MonoWasmThreads) {
+        await mono_wasm_init_diagnostics("env");
+    }
 }
 
 export function mono_wasm_load_runtime(unused?: string, debugLevel?: number): void {