feat(jsii): check that referenced @params exist (#431)

Verify integrity of the documentation by forcing the parameter names
referred to in @param declarations to actually exist. 

Right now it's a WARNING, will be turned into an ERROR some time
in the future. Scrub your sources!

Fixes #422.

packages/jsii/lib/assembler.ts

@@ -7,7 +7,7 @@ import log4js = require('log4js');
 import path = require('path');
 import ts = require('typescript');
 import { JSII_DIAGNOSTICS_CODE } from './compiler';
-import { parseSymbolDocumentation } from './docs';
+import { getReferencedDocParams, parseSymbolDocumentation } from './docs';
 import { Diagnostic, Emitter } from './emitter';
 import literate = require('./literate');
 import { ProjectInfo } from './project-info';
@@ -645,18 +645,10 @@ export class Assembler implements Emitter {
   }
 
   /**
-   * Register documentations on a ``spec.Documentable`` entry.
-   *
-   * @param sym       the symbol holding the JSDoc information
-   * @param documentable the entity being documented
-   *
-   * @returns ``documentable``
+   * Return docs for a symbol
    */
   private _visitDocumentation(sym: ts.Symbol): spec.Docs | undefined {
-    const comment = ts.displayPartsToString(sym.getDocumentationComment(this._typeChecker)).trim();
-
-    // Right here we'll just guess that the first declaration site is the most important one.
-    const result = parseSymbolDocumentation(comment, sym.getJsDocTags());
+    const result = parseSymbolDocumentation(sym, this._typeChecker);
 
     for (const diag of result.diagnostics || []) {
       this._diagnostic(sym.declarations[0],
@@ -669,6 +661,20 @@ export class Assembler implements Emitter {
     return !allUndefined ? result.docs : undefined;
   }
 
+  /**
+   * Check that all parameters the doc block refers to with a @param declaration actually exist
+   */
+  private _validateReferencedDocParams(method: spec.Method, methodSym: ts.Symbol) {
+    const params = getReferencedDocParams(methodSym);
+    const actualNames = new Set((method.parameters || []).map(p => p.name));
+    for (const param of params) {
+      if (!actualNames.has(param)) {
+        this._diagnostic(methodSym.valueDeclaration, ts.DiagnosticCategory.Warning,
+          `In doc block of '${method.name}', '@param ${param}' refers to a nonexistent parameter.`);
+      }
+    }
+  }
+
   private async _visitInterface(type: ts.Type, namespace: string[]): Promise<spec.InterfaceType | undefined> {
     if (LOG.isTraceEnabled()) {
       LOG.trace(`Processing interface: ${colors.gray(namespace.join('.'))}.${colors.cyan(type.symbol.name)}`);
@@ -846,6 +852,8 @@ export class Assembler implements Emitter {
       });
     }
 
+    this._validateReferencedDocParams(method, symbol);
+
     type.methods = type.methods || [];
     if (type.methods.find(m => m.name === method.name && m.static === method.static) != null) {
       LOG.trace(`Dropping re-declaration of ${colors.green(type.fqn)}#${colors.cyan(method.name!)}`);

packages/jsii/lib/docs.ts

@@ -33,7 +33,29 @@
 import spec = require('jsii-spec');
 import ts = require('typescript');
 
-export function parseSymbolDocumentation(comments: string | undefined, tags: ts.JSDocTagInfo[]): DocsParsingResult {
+export function parseSymbolDocumentation(sym: ts.Symbol, typeChecker: ts.TypeChecker): DocsParsingResult {
+    const comment = ts.displayPartsToString(sym.getDocumentationComment(typeChecker)).trim();
+    const tags = sym.getJsDocTags();
+
+    // Right here we'll just guess that the first declaration site is the most important one.
+    return parseDocParts(comment, tags);
+}
+
+/**
+ * Return the list of parameter names that are referenced in the docstring for this symbol
+ */
+export function getReferencedDocParams(sym: ts.Symbol): string[] {
+  const ret = new Array<string>();
+  for (const tag of sym.getJsDocTags()) {
+    if (tag.name === 'param') {
+      const parts = (tag.text || '').split(' ');
+      ret.push(parts[0]);
+    }
+  }
+  return ret;
+}
+
+function parseDocParts(comments: string | undefined, tags: ts.JSDocTagInfo[]): DocsParsingResult {
   const diagnostics = new Array<string>();
   const docs: spec.Docs = {};