http2: expose http2 by default, add NODE_NO_HTTP2

Make `--expose-http2` a non-op,
Expose http2 by default.
Add `NODE_NO_HTTP2=1` to suppress http2

PR-URL: #15685
Reviewed-By: Myles Borins <[email protected]>
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Evan Lucas <[email protected]>

Author: jasnell

doc/api/cli.md

@@ -432,6 +432,13 @@ added: v7.5.0
 
 When set to `1`, process warnings are silenced.
 
+### `NODE_NO_HTTP2=1`
+<!-- YAML
+added: REPLACEME
+-->
+
+When set to `1`, the `http2` module is suppressed.
+
 ### `NODE_OPTIONS=options...`
 <!-- YAML
 added: v8.0.0

doc/api/http2.md

@@ -9,9 +9,6 @@ can be accessed using:
 const http2 = require('http2');
 ```
 
-*Note*: Node.js must be launched with the `--expose-http2` command line flag
-in order to use the `'http2'` module.
-
 ## Core API
 
 The Core API provides a low-level interface designed specifically around

doc/node.1

@@ -130,10 +130,6 @@ Emit pending deprecation warnings.
 .BR \-\-no\-warnings
 Silence all process warnings (including deprecations).
 
-.TP
-.BR \-\-expose\-http2
-Enable the experimental `'http2'` module.
-
 .TP
 .BR \-\-napi\-modules
 Enable loading native modules compiled with the ABI-stable Node.js API (N-API)
@@ -280,6 +276,10 @@ with small\-icu support.
 .BR NODE_NO_WARNINGS =\fI1\fR
 When set to \fI1\fR, process warnings are silenced.
 
+.TP
+.BR NODE_NO_HTTP2 =\fI1\fR
+When set to \fI1\fR, the http2 module is suppressed.
+
 .TP
 .BR NODE_OPTIONS =\fIoptions...\fR
 A space-separated list of command line options. \fBoptions...\fR are interpreted

src/node.cc

@@ -246,8 +246,8 @@ std::string config_warning_file;  // NOLINT(runtime/string)
 // that is used by lib/internal/bootstrap_node.js
 bool config_expose_internals = false;
 
-// Set in node.cc by ParseArgs when --expose-http2 is used.
-bool config_expose_http2 = false;
+// Set to false in node.cc when NODE_NO_HTTP2=1 is used.
+bool config_expose_http2 = true;
 
 bool v8_initialized = false;
 
@@ -3830,7 +3830,6 @@ static void PrintHelp() {
          "  --abort-on-uncaught-exception\n"
          "                             aborting instead of exiting causes a\n"
          "                             core file to be generated for analysis\n"
-         "  --expose-http2             enable experimental HTTP2 support\n"
          "  --trace-warnings           show stack traces on process warnings\n"
          "  --redirect-warnings=file\n"
          "                             write warnings to file instead of\n"
@@ -3894,7 +3893,8 @@ static void PrintHelp() {
 #endif
 #endif
          "NODE_NO_WARNINGS             set to 1 to silence process warnings\n"
-#if !defined(NODE_WITHOUT_NODE_OPTIONS)
+         "NODE_NO_HTTP2                set to 1 to suppress the http2 module\n"
+         #if !defined(NODE_WITHOUT_NODE_OPTIONS)
          "NODE_OPTIONS                 set CLI options in the environment\n"
          "                             via a space-separated list\n"
 #endif
@@ -4173,7 +4173,7 @@ static void ParseArgs(int* argc,
       config_expose_internals = true;
     } else if (strcmp(arg, "--expose-http2") == 0 ||
                strcmp(arg, "--expose_http2") == 0) {
-      config_expose_http2 = true;
+      // Intentional non-op
     } else if (strcmp(arg, "-") == 0) {
       break;
     } else if (strcmp(arg, "--") == 0) {
@@ -4550,6 +4550,12 @@ void Init(int* argc,
         SafeGetenv("NODE_PENDING_DEPRECATION", &text) && text[0] == '1';
   }
 
+  {
+    std::string text;
+    config_expose_http2 =
+      !(SafeGetenv("NODE_NO_HTTP2", &text) && text[0] == '1');
+  }
+
   // Allow for environment set preserving symlinks.
   {
     std::string text;