createProgram calls host.getSourceFile multiple times

TypeScript Version: 3.1.0-dev.20180807

Search Terms:

Repro

declare let oldProgram: ts.Program;
const originalHost = ts.createCompilerHost(true);
const host = {
  ... originalHost,
  getSourceFile(fileName, ...args) {
    console.log(fileName);
    return originalHost.getSoruceFile(fileName, ...args);
  }
const newProgram = ts.createProgram(oldProgram.getRootFileNames(), oldProgram.getCompilerOptions(), host, oldProgram);

Expected behavior:

Each fileName is logged once.

Actual behavior:

If structureIsReused !== Completely fileNames are logged twice: one time from tryReuseStructureFromOldProgram and another time from findSourceFile. That means these SourceFiles are requested multiple times. This is especially a problem with the default CompilerHost which has no caching. It therefore reads and parses each file multiple times, but only the last one is actually used.

Inizia con il repro di createProgram e traccia le chiamate attraverso tryReuseStructureFromOldProgram e findSourceFile. Verifica il comportamento con un CompilerHost che esegua il logging, quindi assicurati che ogni fileName venga richiesto una sola volta quando si riutilizza un programma precedente non completo, senza perdere il comportamento previsto di SourceFile.