1 files changed, 583 insertions, 0 deletions
diff --git a/devtools/client/debugger/src/utils/pause/mapScopes/index.js b/devtools/client/debugger/src/utils/pause/mapScopes/index.js
new file mode 100644
index 0000000000..8736c42218
--- /dev/null
+++ b/devtools/client/debugger/src/utils/pause/mapScopes/index.js
@@ -0,0 +1,583 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at <http://mozilla.org/MPL/2.0/>. */
+
+import {
+  debuggerToSourceMapLocation,
+  sourceMapToDebuggerLocation,
+} from "../../location";
+import { locColumn } from "./locColumn";
+import { loadRangeMetadata, findMatchingRange } from "./rangeMetadata";
+
+// eslint-disable-next-line max-len
+import {
+  findGeneratedReference,
+  findGeneratedImportReference,
+  findGeneratedImportDeclaration,
+} from "./findGeneratedBindingFromPosition";
+import {
+  buildGeneratedBindingList,
+  buildFakeBindingList,
+} from "./buildGeneratedBindingList";
+import {
+  originalRangeStartsInside,
+  getApplicableBindingsForOriginalPosition,
+} from "./getApplicableBindingsForOriginalPosition";
+import { getOptimizedOutGrip } from "./optimizedOut";
+
+import { log } from "../../log";
+
+// Create real location objects for all location start and end.
+//
+// Parser worker returns scopes with location having a sourceId
+// instead of a source object as it doesn't know about main thread source objects.
+function updateLocationsInScopes(state, scopes) {
+  for (const item of scopes) {
+    for (const name of Object.keys(item.bindings)) {
+      for (const ref of item.bindings[name].refs) {
+        const locs = [ref];
+        if (ref.type !== "ref") {
+          locs.push(ref.declaration);
+        }
+        for (const loc of locs) {
+          loc.start = sourceMapToDebuggerLocation(state, loc.start);
+          loc.end = sourceMapToDebuggerLocation(state, loc.end);
+        }
+      }
+    }
+  }
+}
+
+export async function buildMappedScopes(
+  source,
+  content,
+  frame,
+  scopes,
+  thunkArgs
+) {
+  const { getState, parserWorker } = thunkArgs;
+  if (!parserWorker.isLocationSupported(frame.location)) {
+    return null;
+  }
+  const originalAstScopes = await parserWorker.getScopes(frame.location);
+  updateLocationsInScopes(getState(), originalAstScopes);
+  const generatedAstScopes = await parserWorker.getScopes(
+    frame.generatedLocation
+  );
+  updateLocationsInScopes(getState(), generatedAstScopes);
+
+  if (!originalAstScopes || !generatedAstScopes) {
+    return null;
+  }
+
+  const originalRanges = await loadRangeMetadata(
+    frame.location,
+    originalAstScopes,
+    thunkArgs
+  );
+
+  if (hasLineMappings(originalRanges)) {
+    return null;
+  }
+
+  let generatedAstBindings;
+  if (scopes) {
+    generatedAstBindings = buildGeneratedBindingList(
+      scopes,
+      generatedAstScopes,
+      frame.this
+    );
+  } else {
+    generatedAstBindings = buildFakeBindingList(generatedAstScopes);
+  }
+
+  const { mappedOriginalScopes, expressionLookup } =
+    await mapOriginalBindingsToGenerated(
+      source,
+      content,
+      originalRanges,
+      originalAstScopes,
+      generatedAstBindings,
+      thunkArgs
+    );
+
+  const globalLexicalScope = scopes
+    ? getGlobalFromScope(scopes)
+    : generateGlobalFromAst(generatedAstScopes);
+  const mappedGeneratedScopes = generateClientScope(
+    globalLexicalScope,
+    mappedOriginalScopes
+  );
+
+  return isReliableScope(mappedGeneratedScopes)
+    ? { mappings: expressionLookup, scope: mappedGeneratedScopes }
+    : null;
+}
+
+async function mapOriginalBindingsToGenerated(
+  source,
+  content,
+  originalRanges,
+  originalAstScopes,
+  generatedAstBindings,
+  thunkArgs
+) {
+  const expressionLookup = {};
+  const mappedOriginalScopes = [];
+
+  const cachedSourceMaps = batchScopeMappings(
+    originalAstScopes,
+    source,
+    thunkArgs
+  );
+  // Override sourceMapLoader attribute with the special cached SourceMapLoader instance
+  // in order to make it used by all functions used in this method.
+  thunkArgs = { ...thunkArgs, sourceMapLoader: cachedSourceMaps };
+
+  for (const item of originalAstScopes) {
+    const generatedBindings = {};
+
+    for (const name of Object.keys(item.bindings)) {
+      const binding = item.bindings[name];
+
+      const result = await findGeneratedBinding(
+        source,
+        content,
+        name,
+        binding,
+        originalRanges,
+        generatedAstBindings,
+        thunkArgs
+      );
+
+      if (result) {
+        generatedBindings[name] = result.grip;
+
+        if (
+          binding.refs.length !== 0 &&
+          // These are assigned depth-first, so we don't want shadowed
+          // bindings in parent scopes overwriting the expression.
+          !Object.prototype.hasOwnProperty.call(expressionLookup, name)
+        ) {
+          expressionLookup[name] = result.expression;
+        }
+      }
+    }
+
+    mappedOriginalScopes.push({
+      ...item,
+      generatedBindings,
+    });
+  }
+
+  return {
+    mappedOriginalScopes,
+    expressionLookup,
+  };
+}
+
+/**
+ * Consider a scope and its parents reliable if the vast majority of its
+ * bindings were successfully mapped to generated scope bindings.
+ */
+function isReliableScope(scope) {
+  let totalBindings = 0;
+  let unknownBindings = 0;
+
+  for (let s = scope; s; s = s.parent) {
+    const vars = s.bindings?.variables || {};
+    for (const key of Object.keys(vars)) {
+      const binding = vars[key];
+
+      totalBindings += 1;
+      if (
+        binding.value &&
+        typeof binding.value === "object" &&
+        (binding.value.type === "unscoped" || binding.value.type === "unmapped")
+      ) {
+        unknownBindings += 1;
+      }
+    }
+  }
+
+  // As determined by fair dice roll.
+  return totalBindings === 0 || unknownBindings / totalBindings < 0.25;
+}
+
+function hasLineMappings(ranges) {
+  return ranges.every(
+    range => range.columnStart === 0 && range.columnEnd === Infinity
+  );
+}
+
+/**
+ * Build a special SourceMapLoader instance, based on the one passed in thunkArgs,
+ * which will both:
+ *   - preload generated ranges/locations for original locations mentioned
+ *     in originalAstScopes
+ *   - cache the requests to fetch these genereated ranges/locations
+ */
+function batchScopeMappings(originalAstScopes, source, thunkArgs) {
+  const { sourceMapLoader } = thunkArgs;
+  const precalculatedRanges = new Map();
+  const precalculatedLocations = new Map();
+
+  // Explicitly dispatch all of the sourcemap requests synchronously up front so
+  // that they will be batched into a single request for the worker to process.
+  for (const item of originalAstScopes) {
+    for (const name of Object.keys(item.bindings)) {
+      for (const ref of item.bindings[name].refs) {
+        const locs = [ref];
+        if (ref.type !== "ref") {
+          locs.push(ref.declaration);
+        }
+
+        for (const loc of locs) {
+          precalculatedRanges.set(
+            buildLocationKey(loc.start),
+            sourceMapLoader.getGeneratedRanges(
+              debuggerToSourceMapLocation(loc.start)
+            )
+          );
+          precalculatedLocations.set(
+            buildLocationKey(loc.start),
+            sourceMapLoader.getGeneratedLocation(
+              debuggerToSourceMapLocation(loc.start)
+            )
+          );
+          precalculatedLocations.set(
+            buildLocationKey(loc.end),
+            sourceMapLoader.getGeneratedLocation(
+              debuggerToSourceMapLocation(loc.end)
+            )
+          );
+        }
+      }
+    }
+  }
+
+  return {
+    async getGeneratedRanges(pos) {
+      const key = buildLocationKey(pos);
+
+      if (!precalculatedRanges.has(key)) {
+        log("Bad precalculated mapping");
+        return sourceMapLoader.getGeneratedRanges(
+          debuggerToSourceMapLocation(pos)
+        );
+      }
+      return precalculatedRanges.get(key);
+    },
+
+    async getGeneratedLocation(pos) {
+      const key = buildLocationKey(pos);
+
+      if (!precalculatedLocations.has(key)) {
+        log("Bad precalculated mapping");
+        return sourceMapLoader.getGeneratedLocation(
+          debuggerToSourceMapLocation(pos)
+        );
+      }
+      return precalculatedLocations.get(key);
+    },
+  };
+}
+function buildLocationKey(loc) {
+  return `${loc.line}:${locColumn(loc)}`;
+}
+
+function generateClientScope(globalLexicalScope, originalScopes) {
+  // Build a structure similar to the client's linked scope object using
+  // the original AST scopes, but pulling in the generated bindings
+  // linked to each scope.
+  const result = originalScopes
+    .slice(0, -2)
+    .reverse()
+    .reduce((acc, orig, i) => {
+      const {
+        // The 'this' binding data we have is handled independently, so
+        // the binding data is not included here.
+        // eslint-disable-next-line no-unused-vars
+        this: _this,
+        ...variables
+      } = orig.generatedBindings;
+
+      return {
+        parent: acc,
+        actor: `originalActor${i}`,
+        type: orig.type,
+        scopeKind: orig.scopeKind,
+        bindings: {
+          arguments: [],
+          variables,
+        },
+        ...(orig.type === "function"
+          ? {
+              function: {
+                displayName: orig.displayName,
+              },
+            }
+          : null),
+        ...(orig.type === "block"
+          ? {
+              block: {
+                displayName: orig.displayName,
+              },
+            }
+          : null),
+      };
+    }, globalLexicalScope);
+
+  // The rendering logic in getScope 'this' bindings only runs on the current
+  // selected frame scope, so we pluck out the 'this' binding that was mapped,
+  // and put it in a special location
+  const thisScope = originalScopes.find(scope => scope.bindings.this);
+  if (result.bindings && thisScope) {
+    result.bindings.this = thisScope.generatedBindings.this || null;
+  }
+
+  return result;
+}
+
+function getGlobalFromScope(scopes) {
+  // Pull the root object scope and root lexical scope to reuse them in
+  // our mapped scopes. This assumes that file being processed is
+  // a CommonJS or ES6 module, which might not be ideal. Potentially
+  // should add some logic to try to detect those cases?
+  let globalLexicalScope = null;
+  for (let s = scopes; s.parent; s = s.parent) {
+    globalLexicalScope = s;
+  }
+  if (!globalLexicalScope) {
+    throw new Error("Assertion failure - there should always be a scope");
+  }
+  return globalLexicalScope;
+}
+
+function generateGlobalFromAst(generatedScopes) {
+  const globalLexicalAst = generatedScopes[generatedScopes.length - 2];
+  if (!globalLexicalAst) {
+    throw new Error("Assertion failure - there should always be a scope");
+  }
+  return {
+    actor: "generatedActor1",
+    type: "block",
+    scopeKind: "",
+    bindings: {
+      arguments: [],
+      variables: Object.fromEntries(
+        Object.keys(globalLexicalAst).map(key => [key, getOptimizedOutGrip()])
+      ),
+    },
+    parent: {
+      actor: "generatedActor0",
+      object: getOptimizedOutGrip(),
+      scopeKind: "",
+      type: "object",
+    },
+  };
+}
+
+function hasValidIdent(range, pos) {
+  return (
+    range.type === "match" ||
+    // For declarations, we allow the range on the identifier to be a
+    // more general "contains" to increase the chances of a match.
+    (pos.type !== "ref" && range.type === "contains")
+  );
+}
+
+// eslint-disable-next-line complexity
+async function findGeneratedBinding(
+  source,
+  content,
+  name,
+  originalBinding,
+  originalRanges,
+  generatedAstBindings,
+  thunkArgs
+) {
+  // If there are no references to the implicits, then we have no way to
+  // even attempt to map it back to the original since there is no location
+  // data to use. Bail out instead of just showing it as unmapped.
+  if (
+    originalBinding.type === "implicit" &&
+    !originalBinding.refs.some(item => item.type === "ref")
+  ) {
+    return null;
+  }
+
+  const loadApplicableBindings = async (pos, locationType) => {
+    let applicableBindings = await getApplicableBindingsForOriginalPosition(
+      generatedAstBindings,
+      source,
+      pos,
+      originalBinding.type,
+      locationType,
+      thunkArgs
+    );
+    if (applicableBindings.length) {
+      hadApplicableBindings = true;
+    }
+    if (locationType === "ref") {
+      // Some tooling creates ranges that map a line as a whole, which is useful
+      // for step-debugging, but can easily lead to finding the wrong binding.
+      // To avoid these false-positives, we entirely ignore bindings matched
+      // by ranges that cover full lines.
+      applicableBindings = applicableBindings.filter(
+        ({ range }) =>
+          !(range.start.column === 0 && range.end.column === Infinity)
+      );
+    }
+    if (
+      locationType !== "ref" &&
+      !(await originalRangeStartsInside(pos, thunkArgs))
+    ) {
+      applicableBindings = [];
+    }
+    return applicableBindings;
+  };
+
+  const { refs } = originalBinding;
+
+  let hadApplicableBindings = false;
+  let genContent = null;
+  for (const pos of refs) {
+    const applicableBindings = await loadApplicableBindings(pos, pos.type);
+
+    const range = findMatchingRange(originalRanges, pos);
+    if (range && hasValidIdent(range, pos)) {
+      if (originalBinding.type === "import") {
+        genContent = await findGeneratedImportReference(applicableBindings);
+      } else {
+        genContent = await findGeneratedReference(applicableBindings);
+      }
+    }
+
+    if (
+      (pos.type === "class-decl" || pos.type === "class-inner") &&
+      content.contentType &&
+      content.contentType.match(/\/typescript/)
+    ) {
+      const declRange = findMatchingRange(originalRanges, pos.declaration);
+      if (declRange && declRange.type !== "multiple") {
+        const applicableDeclBindings = await loadApplicableBindings(
+          pos.declaration,
+          pos.type
+        );
+
+        // Resolve to first binding in the range
+        const declContent = await findGeneratedReference(
+          applicableDeclBindings
+        );
+
+        if (declContent) {
+          // Prefer the declaration mapping in this case because TS sometimes
+          // maps class declaration names to "export.Foo = Foo;" or to
+          // the decorator logic itself
+          genContent = declContent;
+        }
+      }
+    }
+
+    if (
+      !genContent &&
+      pos.type === "import-decl" &&
+      typeof pos.importName === "string"
+    ) {
+      const { importName } = pos;
+      const declRange = findMatchingRange(originalRanges, pos.declaration);
+
+      // The import declaration should have an original position mapping,
+      // but otherwise we don't really have preferences on the range type
+      // because it can have multiple bindings, but we do want to make sure
+      // that all of the bindings that match the range are part of the same
+      // import declaration.
+      if (declRange?.singleDeclaration) {
+        const applicableDeclBindings = await loadApplicableBindings(
+          pos.declaration,
+          pos.type
+        );
+
+        // match the import declaration location
+        genContent = await findGeneratedImportDeclaration(
+          applicableDeclBindings,
+          importName
+        );
+      }
+    }
+
+    if (genContent) {
+      break;
+    }
+  }
+
+  if (genContent && genContent.desc) {
+    return {
+      grip: genContent.desc,
+      expression: genContent.expression,
+    };
+  } else if (genContent) {
+    // If there is no descriptor for 'this', then this is not the top-level
+    // 'this' that the server gave us a binding for, and we can just ignore it.
+    if (name === "this") {
+      return null;
+    }
+
+    // If the location is found but the descriptor is not, then it
+    // means that the server scope information didn't match the scope
+    // information from the DevTools parsed scopes.
+    return {
+      grip: {
+        configurable: false,
+        enumerable: true,
+        writable: false,
+        value: {
+          type: "unscoped",
+          unscoped: true,
+
+          // HACK: Until support for "unscoped" lands in devtools-reps,
+          // this will make these show as (unavailable).
+          missingArguments: true,
+        },
+      },
+      expression: null,
+    };
+  } else if (!hadApplicableBindings && name !== "this") {
+    // If there were no applicable bindings to consider while searching for
+    // matching bindings, then the source map for this file didn't make any
+    // attempt to map the binding, and that most likely means that the
+    // code was entirely emitted from the output code.
+    return {
+      grip: getOptimizedOutGrip(),
+      expression: `
+        (() => {
+          throw new Error('"' + ${JSON.stringify(
+            name
+          )} + '" has been optimized out.');
+        })()
+      `,
+    };
+  }
+
+  // If no location mapping is found, then the map is bad, or
+  // the map is okay but it original location is inside
+  // of some scope, but the generated location is outside, leading
+  // us to search for bindings that don't technically exist.
+  return {
+    grip: {
+      configurable: false,
+      enumerable: true,
+      writable: false,
+      value: {
+        type: "unmapped",
+        unmapped: true,
+
+        // HACK: Until support for "unmapped" lands in devtools-reps,
+        // this will make these show as (unavailable).
+        missingArguments: true,
+      },
+    },
+    expression: null,
+  };
+}