Repository: TypeScript
Issue: Extend the tsc --listFiles option to specify an output file for the list
Labels: Suggestion,Awaiting More Feedback

### 🔍 Search Terms

listFiles redirect

### ✅ Viability Checklist

- [x] This wouldn't be a breaking change in existing TypeScript/JavaScript code
- [x] This wouldn't change the runtime behavior of existing JavaScript code
- [x] This could be implemented without emitting different JS based on the types of the expressions
- [x] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
- [x] This isn't a request to add a new utility type: https://github.com/microsoft/TypeScript/wiki/No-New-Utility-Types
- [x] This feature would agree with the rest of our Design Goals: https://github.com/Microsoft/TypeScript/wiki/TypeScript-Design-Goals

### ⭐ Suggestion

I would like to be able to separate the output from the listFiles option from the rest of the tsc output (eg. compilation errors). I think the easiest way to do this would be to allow an output file to be specified.

### 📃 Motivating Example

While integrating typescript scripts into a `make` build process, I wanted to generate dependency files to facilitate incremental builds. Initially I tried running with the listFiles flag and capturing the output to create the dependency files to include in my makefile, however I quickly ran into the following issues:

1. Compilation errors and the file list are both output to stdout
2. By default capturing the output of a subshell stops it being output to the console

My initial solution was to run `tsc` twice, once with `--listFiles --noEmit` and then again without those options. This resulted in excessive build times as I needed to do this for lots of scripts.

For now I have solved the issue with the following bash script that attempts to extract the compilation output from the listFiles output:

```shell
#!/usr/bin/env bash

set -e

INPUT_DIR=$1
DEPS_FILE=$2

SQL_SCRIPT=$INPUT_DIR/sql/test.sql

rm -rf "${INPUT_DIR:?}/"lib
if INPUT_FILES=$(npx tsc --project "$INPUT_DIR"/tsconfig.json --listFiles); then
  echo "$SQL_SCRIPT: $(echo "$INPUT_FILES" | sed 's/$/ \\/')" > "$DEPS_FILE"
  cd "$INPUT_DIR"/lib
  node index.js
else
  EXIT_CODE=$?
  # the following assumes that all important compilation output contains the text ': error'
  echo "$INPUT_FILES" | grep ": error"
  exit $EXIT_CODE
fi
```

However it would be much simpler if I could separate the listFiles output using the `tsc` command, eg:

```shell
#!/usr/bin/env bash

set -e

INPUT_DIR=$1
DEPS_FILE=$2

SQL_SCRIPT=$INPUT_DIR/sql/test.sql

rm -rf "${INPUT_DIR:?}/"lib
npx tsc --project "$INPUT_DIR"/tsconfig.json --listFilesTo $INPUT_DIR/ts/deps
echo "$SQL_SCRIPT: $(sed 's/$/ \\/' $INPUT_DIR/ts/deps)" > "$DEPS_FILE"
cd "$INPUT_DIR"/lib
node index.js
```


### 💻 Use Cases

1. What do you want to use this for? : I want to simply integrate the listFiles output into a make based build environment
3. What shortcomings exist with current approaches? : The listFiles and compilation error outputs are mixed together
4. What workarounds are you using in the meantime? : A complicated shell script that tries to extract the compilation output from the listFiles output