What is the best way to utilize the typescript module for detecting and managing typescript errors and warnings in your code?

Question

What is the best way to utilize the typescript module for detecting and managing typescript errors and warnings in your code?

Currently, I am experimenting with the typescript module to programmatically detect typescript errors. Below is a simplified version of what I have been working on:

var ts=require('typescript')

var file_content=`
interface Message{
  a:string
  b:number
}
var a:Message={a:'hello'}  
`
var options={
  compilerOptions:{
    module:'ES2015',
    target:'ES2015',
    inlineSourceMap:true
  },
  reportDiagnostics: true
}
const typescript_output = ts.transpileModule(file_content,options)
console.log(typescript_output.diagnostics)

The issue here is that when I execute the code using node, it consistently displays an empty array for the diagnostics, despite having a typescript error in the content stored in the file_content variable.

I would like to know: What is the correct approach to utilize the typescript module API to retrieve typescript errors?

typescript

Answer 1

Answer №1

transpileModule doesn't report type errors intentionally. According to information on the wiki, it is necessary to create a complete compiler in order to receive diagnostic messages. By utilizing their provided sample code, any type errors will be accurately detected:

const ts = require('typescript')

function compile (fileNames, options) {
  const program = ts.createProgram(fileNames, options)
  const emitResult = program.emit()

  const allDiagnostics = ts
    .getPreEmitDiagnostics(program)
    .concat(emitResult.diagnostics)

  allDiagnostics.forEach(diagnostic => {
    if (diagnostic.file) {
      const { line, character } = ts.getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start)
      const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n')
      console.log(`${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`)
    } else {
      console.log(ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n'))
    }
  })

  const exitCode = emitResult.emitSkipped ? 1 : 0
  console.log(`Process exiting with code '${exitCode}'.`)
  process.exit(exitCode)
}

const options = {
  compilerOptions: {
    module: 'ES2015',
    target: 'ES2015',
    inlineSourceMap: true
  },
  reportDiagnostics: true
}

compile(process.argv.slice(2), options)

An issue that may arise is the necessity of having files on disk, which differs from your string-based approach. Should there not be a more suitable API available, using a temporary file could potentially circumvent this limitation.

Answer 2

transpileModule doesn't report type errors intentionally. According to information on the wiki, it is necessary to create a complete compiler in order to receive diagnostic messages. By utilizing their provided sample code, any type errors will be accurately detected:

const ts = require('typescript')

function compile (fileNames, options) {
  const program = ts.createProgram(fileNames, options)
  const emitResult = program.emit()

  const allDiagnostics = ts
    .getPreEmitDiagnostics(program)
    .concat(emitResult.diagnostics)

  allDiagnostics.forEach(diagnostic => {
    if (diagnostic.file) {
      const { line, character } = ts.getLineAndCharacterOfPosition(diagnostic.file, diagnostic.start)
      const message = ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n')
      console.log(`${diagnostic.file.fileName} (${line + 1},${character + 1}): ${message}`)
    } else {
      console.log(ts.flattenDiagnosticMessageText(diagnostic.messageText, '\n'))
    }
  })

  const exitCode = emitResult.emitSkipped ? 1 : 0
  console.log(`Process exiting with code '${exitCode}'.`)
  process.exit(exitCode)
}

const options = {
  compilerOptions: {
    module: 'ES2015',
    target: 'ES2015',
    inlineSourceMap: true
  },
  reportDiagnostics: true
}

compile(process.argv.slice(2), options)

An issue that may arise is the necessity of having files on disk, which differs from your string-based approach. Should there not be a more suitable API available, using a temporary file could potentially circumvent this limitation.

Answer 3

Answer №2

If you're encountering issues with module resolution, consider implementing the following code snippet:

    tsconfig.compilerOptions.sourceRoot = objDir;
    const host = ts.createCompilerHost(tsconfig.compilerOptions);
    const cache = ts.createModuleResolutionCache(objDir, x => x, tsconfig.compilerOptions);

    host.resolveModuleNames = function resolveModuleNames(moduleNames: readonly string[], containingFile: string, reusedNames: readonly string[] | undefined,
        redirectedReference: ts.ResolvedProjectReference | undefined, options: ts.CompilerOptions,
        containingSourceFile?: ts.SourceFile): (ts.ResolvedModule | undefined)[] {
        // Custom implementation
        return moduleNames.map(function (moduleName: string): ts.ResolvedModule | undefined {
            if (moduleName.startsWith("node:")) return undefined; 
            const cacheMode = tsconfig.compilerOptions.module < 5 ? ts.ModuleKind.CommonJS : ts.ModuleKind.ESNext;
            const res = ts.resolveModuleName(moduleName, containingFile, options, host, cache, redirectedReference, cacheMode);
            if (res.resolvedModule === undefined) {
                for (const file of files) {
                    if (path.basename(file).substring(0, path.basename(file).length - path.extname(file).length) == moduleName) { 
                        const ret: ts.ResolvedModuleFull = { isExternalLibraryImport: file.split(path.sep).some(x => x == "node_modules"), resolvedFileName: file, extension: ts.Extension[path.extname(file)] };
                        cache.getOrCreateCacheForModuleName(moduleName, cacheMode, redirectedReference).set(objDir, { resolvedModule: ret });
                        return ret;
                    }
                }
            }
            return res.resolvedModule;
        });
    }

    const program = ts.createProgram(objFiles, tsconfig.compilerOptions, host, null, tsconfig.errors);
    const emitResult = program.emit();

Answer 4

If you're encountering issues with module resolution, consider implementing the following code snippet:

    tsconfig.compilerOptions.sourceRoot = objDir;
    const host = ts.createCompilerHost(tsconfig.compilerOptions);
    const cache = ts.createModuleResolutionCache(objDir, x => x, tsconfig.compilerOptions);

    host.resolveModuleNames = function resolveModuleNames(moduleNames: readonly string[], containingFile: string, reusedNames: readonly string[] | undefined,
        redirectedReference: ts.ResolvedProjectReference | undefined, options: ts.CompilerOptions,
        containingSourceFile?: ts.SourceFile): (ts.ResolvedModule | undefined)[] {
        // Custom implementation
        return moduleNames.map(function (moduleName: string): ts.ResolvedModule | undefined {
            if (moduleName.startsWith("node:")) return undefined; 
            const cacheMode = tsconfig.compilerOptions.module < 5 ? ts.ModuleKind.CommonJS : ts.ModuleKind.ESNext;
            const res = ts.resolveModuleName(moduleName, containingFile, options, host, cache, redirectedReference, cacheMode);
            if (res.resolvedModule === undefined) {
                for (const file of files) {
                    if (path.basename(file).substring(0, path.basename(file).length - path.extname(file).length) == moduleName) { 
                        const ret: ts.ResolvedModuleFull = { isExternalLibraryImport: file.split(path.sep).some(x => x == "node_modules"), resolvedFileName: file, extension: ts.Extension[path.extname(file)] };
                        cache.getOrCreateCacheForModuleName(moduleName, cacheMode, redirectedReference).set(objDir, { resolvedModule: ret });
                        return ret;
                    }
                }
            }
            return res.resolvedModule;
        });
    }

    const program = ts.createProgram(objFiles, tsconfig.compilerOptions, host, null, tsconfig.errors);
    const emitResult = program.emit();

What is the best way to utilize the typescript module for detecting and managing typescript errors and warnings in your code?

Answer №1

Answer №2

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