script: Fix panic in compressedTexSubImage2D when no base image exists (#44050)

Calling `compressedTexSubImage2D` without a prior `compressedTexImage2D`
for the same texture target and level caused the panic at
`tex_image_2d.rs:633` because `image_info_for_target` returned `None`
and `.unwrap()` was called on it.

Per the WebGL spec, this should generate `GL_INVALID_OPERATION` instead
of panicking. So this PR replaces the unwrap with proper error handling.
And also includes a WPT crash test that reproduces the original panic.

Fixes #43527

---------

Signed-off-by: thebabalola <t.babalolajoseph@gmail.com>

components/script/dom/webgl/validations/tex_image_2d.rs

@@ -53,6 +53,8 @@ pub(crate) enum TexImageValidationError {
     InvalidCompressionFormat,
     /// Invalid X/Y texture offset parameters.
     InvalidOffsets,
+    /// No base image has been defined for this texture target and level.
+    MissingBaseTexture,
 }
 
 impl std::error::Error for TexImageValidationError {}
@@ -80,6 +82,7 @@ impl fmt::Display for TexImageValidationError {
             NonPotTexture => "Expected a power of two texture",
             InvalidCompressionFormat => "Unrecognized texture compression format",
             InvalidOffsets => "Invalid X/Y texture offset parameters",
+            MissingBaseTexture => "No base image defined for this texture target and level",
         };
         write!(f, "TexImageValidationError({})", description)
     }
@@ -630,7 +633,12 @@ impl WebGLValidator for CompressedTexSubImage2DValidator<'_> {
             compression,
         } = self.compression_validator.validate()?;
 
-        let tex_info = texture.image_info_for_target(&target, level).unwrap();
+        // GL_INVALID_OPERATION is generated if no base image has been defined
+        // for this texture target and level via compressedTexImage2D.
+        let Some(tex_info) = texture.image_info_for_target(&target, level) else {
+            context.webgl_error(InvalidOperation);
+            return Err(TexImageValidationError::MissingBaseTexture);
+        };
 
         // GL_INVALID_VALUE is generated if:
         //   - xoffset or yoffset is less than 0

tests/wpt/meta/MANIFEST.json

@@ -244603,7 +244603,7 @@
      "before-after-pseudo-element-scrolling.html": [
       "805c01af85b7e01f73bda4a1ee90db50fa83ce60",
       [
-       "css/css-overflow/before-after-pseudo-element-scrolling.html",
+       null,
        [
         [
          "/css/css-overflow/reference/before-after-pseudo-element-scrolling-ref.html",
@@ -295379,7 +295379,7 @@
       "word-break-keep-all-011.html": [
        "c1d7af2496894ef609115d3b4fc01cb54ffb32a7",
        [
-        "css/css-text/word-break/word-break-keep-all-011.html",
+        null,
         [
          [
           "/css/css-text/word-break/reference/word-break-keep-all-011-ref.html",
@@ -378843,7 +378843,7 @@
        "caret-visibility-after-creation-in-script.html": [
         "6e9e8fd1618fd9fd4bb90a1bc2a8199c2e447764",
         [
-         "html/rendering/replaced-elements/the-textarea-element/caret-visibility-after-creation-in-script.html",
+         null,
          [
           [
            "/html/rendering/replaced-elements/the-textarea-element/caret-visibility-after-creation-in-script-ref.html",
@@ -563188,10 +563188,6 @@
      "a5e37dce95b00834aa3d3b58008762f5801e9e5d",
      []
     ],
-    "browser.runtime.extension.js": [
-     "c41a1b795ea829493364767e9ea3403f0586c1bc",
-     []
-    ],
     "resources": {
      "runtime": {
       "background.js": [
@@ -902757,6 +902753,15 @@
      ]
     }
    },
+   "web-extensions": {
+    "browser.runtime.extension.js": [
+     "c41a1b795ea829493364767e9ea3403f0586c1bc",
+     [
+      "web-extensions/browser.runtime.extension.html",
+      {}
+     ]
+    ]
+   },
    "web-locks": {
     "acquire.https.any.js": [
      "54ae6f30e7add6f45c6b5ba7161999b5a6078871",
@@ -915672,6 +915677,13 @@
       {}
      ]
     ],
+    "compressed-tex-sub-image-2d-without-base-image.html": [
+     "4627a2b4ba3c6759d5bd1194c6a86c97b466165f",
+     [
+      null,
+      {}
+     ]
+    ],
     "compressedTexImage2D.html": [
      "a974c65002448c0df1beb97f93d5cd1476f254ca",
      [

tests/wpt/tests/webgl/compressed-tex-sub-image-2d-without-base-image.html

@@ -0,0 +1,37 @@
+<!doctype html>
+<title>compressedTexSubImage2D without prior compressedTexImage2D generates INVALID_OPERATION</title>
+<link rel=author title="Babalola Taiwo Joseph" href=mailto:t.babalolajoseph@gmail.com>
+<link rel=help href=https://www.khronos.org/registry/webgl/specs/latest/#5.14.8>
+<script src=/resources/testharness.js></script>
+<script src=/resources/testharnessreport.js></script>
+
+<div id=log></div>
+<script>
+test(function() {
+  var canvas = document.createElement("canvas");
+  var gl = canvas.getContext("webgl");
+  assert_true(!!gl, "WebGL context should be available");
+
+  var s3tc = gl.getExtension("WEBGL_compressed_texture_s3tc");
+  var etc1 = gl.getExtension("WEBGL_compressed_texture_etc1");
+
+  var format, dataSize;
+  if (s3tc) {
+    format = s3tc.COMPRESSED_RGB_S3TC_DXT1_EXT;
+    dataSize = 8;
+  } else if (etc1) {
+    format = etc1.COMPRESSED_RGB_ETC1_WEBGL;
+    dataSize = 8;
+  }
+
+  assert_true(!!format, "A supported compressed texture format must be available");
+
+  var texture = gl.createTexture();
+  gl.bindTexture(gl.TEXTURE_2D, texture);
+
+  gl.compressedTexSubImage2D(gl.TEXTURE_2D, 0, 0, 0, 4, 4, format, new Uint8Array(dataSize));
+
+  assert_equals(gl.getError(), gl.INVALID_OPERATION,
+    "compressedTexSubImage2D without a prior compressedTexImage2D should generate INVALID_OPERATION");
+}, "compressedTexSubImage2D without base image generates INVALID_OPERATION");
+</script>