[api-extractor] Fix issue where API signatures were sometimes truncated

apps/api-extractor/src/generators/ApiModelGenerator.ts

@@ -268,7 +268,7 @@ export class ApiModelGenerator {
 
       const excerptTokens: IExcerptToken[] = ExcerptBuilder.build({
         startingNode: astDeclaration.declaration,
-        nodeToStopAt: ts.SyntaxKind.FirstPunctuation,  // FirstPunctuation = "{"
+        stopBeforeChildKind: ts.SyntaxKind.FirstPunctuation,  // FirstPunctuation = "{"
         nodesToCapture
       });
       const docComment: tsdoc.DocComment | undefined = this._collector.fetchMetadata(astDeclaration).tsdocComment;
@@ -328,7 +328,7 @@ export class ApiModelGenerator {
     if (apiEnum === undefined) {
       const excerptTokens: IExcerptToken[] = ExcerptBuilder.build({
         startingNode: astDeclaration.declaration,
-        nodeToStopAt: ts.SyntaxKind.FirstPunctuation  // FirstPunctuation = "{"
+        stopBeforeChildKind: ts.SyntaxKind.FirstPunctuation  // FirstPunctuation = "{"
       });
 
       const docComment: tsdoc.DocComment | undefined = this._collector.fetchMetadata(astDeclaration).tsdocComment;
@@ -467,7 +467,7 @@ export class ApiModelGenerator {
 
       const excerptTokens: IExcerptToken[] = ExcerptBuilder.build({
         startingNode: astDeclaration.declaration,
-        nodeToStopAt: ts.SyntaxKind.FirstPunctuation,  // FirstPunctuation = "{"
+        stopBeforeChildKind: ts.SyntaxKind.FirstPunctuation,  // FirstPunctuation = "{"
         nodesToCapture
       });
 
@@ -563,7 +563,7 @@ export class ApiModelGenerator {
     if (apiNamespace === undefined) {
       const excerptTokens: IExcerptToken[] = ExcerptBuilder.build({
         startingNode: astDeclaration.declaration,
-        nodeToStopAt: ts.SyntaxKind.ModuleBlock  // ModuleBlock = the "{ ... }" block
+        stopBeforeChildKind: ts.SyntaxKind.ModuleBlock  // ModuleBlock = the "{ ... }" block
       });
 
       const docComment: tsdoc.DocComment | undefined = this._collector.fetchMetadata(astDeclaration).tsdocComment;

apps/api-extractor/src/generators/ExcerptBuilder.ts

@@ -32,13 +32,18 @@ export interface ISignatureBuilderOptions {
   /**
    * The AST node that we will traverse to extract tokens
    */
-
   startingNode: ts.Node;
+
   /**
-   * An AST node to stop at (e.g. the "{" after a class declaration).
-   * If omitted, then all child nodes for `startingNode` will be processed
+   * Normally, the excerpt will include all child nodes for `startingNode`; whereas if `childKindToStopBefore`
+   * is specified, then the node traversal will stop before (i.e. excluding) the first immediate child
+   * of `startingNode` with the specified syntax kind.
+   *
+   * @remarks
+   * For example, suppose the signature is `interface X: Y { z: string }`.  The token `{` has syntax kind
+   * `ts.SyntaxKind.FirstPunctuation`, so we can specify that to truncate the excerpt to `interface X: Y`.
    */
-  nodeToStopAt?: ts.SyntaxKind;
+  stopBeforeChildKind?: ts.SyntaxKind;
 
   /**
    * A list of child nodes whose token ranges we want to capture
@@ -50,7 +55,9 @@ export interface ISignatureBuilderOptions {
  * Internal state for ExcerptBuilder
  */
 interface IBuildSpanState {
-  nodeToStopAt?: ts.SyntaxKind;
+  startingNode: ts.Node;
+  stopBeforeChildKind: ts.SyntaxKind | undefined;
+
   tokenRangesByNode: Map<ts.Node, IExcerptTokenRange>;
 
   /**
@@ -75,7 +82,8 @@ export class ExcerptBuilder {
     const excerptTokens: IExcerptToken[] = [];
 
     ExcerptBuilder._buildSpan(excerptTokens, span, {
-      nodeToStopAt: options.nodeToStopAt,
+      startingNode: options.startingNode,
+      stopBeforeChildKind: options.stopBeforeChildKind,
       tokenRangesByNode,
       disableMergingForNextToken: false
     });
@@ -88,11 +96,6 @@ export class ExcerptBuilder {
   }
 
   private static _buildSpan(excerptTokens: IExcerptToken[], span: Span, state: IBuildSpanState): boolean {
-
-    if (state.nodeToStopAt && span.kind === state.nodeToStopAt) {
-      return false;
-    }
-
     if (span.kind === ts.SyntaxKind.JSDocComment) {
       // Discard any comments
       return true;
@@ -119,6 +122,13 @@ export class ExcerptBuilder {
     }
 
     for (const child of span.children) {
+      if (span.node === state.startingNode) {
+        if (state.stopBeforeChildKind && child.kind === state.stopBeforeChildKind) {
+          // We reached the a child whose kind is stopBeforeChildKind, so stop traversing
+          return false;
+        }
+      }
+
       if (!this._buildSpan(excerptTokens, child, state)) {
         return false;
       }

common/changes/@microsoft/api-extractor/octogonz-ae-1249_2019-04-30-05-00.json

@@ -0,0 +1,11 @@
+{
+  "changes": [
+    {
+      "packageName": "@microsoft/api-extractor",
+      "comment": "Fix an issue where API signatures were sometimes truncated in the .api.json file (GitHub #1249)",
+      "type": "patch"
+    }
+  ],
+  "packageName": "@microsoft/api-extractor",
+  "email": "[email protected]"
+}