Fix flag extraction bug in extract_desugar_pgcfg_flags

Previous implementation would just blindly split the shrinker_config field as a string by spaces. This logic is incorrect. The right thing to do is to tell the program what format the data is coming in as (i.e. define the struct for the shrinker config flags), and unmarshall the JSON bytes with that in mind.

This CL also enhances the test for this tool to better reflect the actual intended logic.

Part of #122

PiperOrigin-RevId: 601239403
Change-Id: Id4d3e5b7daa92f3d07d588894234f7a2add41f1e

src/tools/extract_desugar_pgcfg_flags/extract_desugar_pgcfg_flags.go

@@ -18,7 +18,6 @@ package main
 import (
 	"encoding/json"
 	"flag"
-	"fmt"
 	"io/ioutil"
 	"log"
 	"os"
@@ -57,15 +56,15 @@ func main() {
 
 	// The r8 desugar config json schema is pretty complicated (+subject to change), and we only
 	// need one field, so instead of reading into a predefined data structure, we just read into a
-	// map[string]any to keep things simple.
-	var result map[string]any
+	// simple struct containing only the relevant shrinker_config string[] field.
+	type shrinkerConfig struct {
+		ShrinkerConfigFlags []string `json:"shrinker_config"`
+	}
+
+	var result shrinkerConfig
 	json.Unmarshal(jsonBytes, &result)
 
-	// Read the shrinker_config field as a string, then trim the demarcating [ ] characters.
-	shrinkerConfigAsString := strings.TrimRight(strings.TrimLeft(fmt.Sprintf("%v", result["shrinker_config"]), "["), "]")
-	shrinkerConfigList := strings.Split(shrinkerConfigAsString, " ")
-	// Massage into newline-separated flag list.
-	shrinkerConfigFlags := strings.Join(shrinkerConfigList, "\n")
+	shrinkerConfigFlags := strings.Join(result.ShrinkerConfigFlags, "\n")
 
 	// Write the shrinker config to the output file
 	shrinkerConfigFile, err := os.Create(*outputFileFlag)

src/tools/extract_desugar_pgcfg_flags/extract_desugar_pgcfg_flags_test.sh

@@ -41,13 +41,13 @@ set -euxo pipefail
 # Create dummy data
 dummy_json_file="$(mktemp)"
 # Dummy data: shrinker_config is a list of strings, and another unrelated field.
-echo "{\"shrinker_config\": [\"a\", \"b\", \"c\"], \"foo\": \"bar\"}" > "$dummy_json_file"
+echo "{\"shrinker_config\": [\"-keepclassmembers a b c\", \"foobar\", \"-someflag 1 2 3\"], \"foo\": \"bar\"}" > "$dummy_json_file"
 
 # Dummy output dummy output file
-test_output_file="$(mktemp)"
-expected_output_file="$(mktemp)"
+test_output_file="$(mktemp -p /tmp test.XXXX)"
+expected_output_file="$(mktemp -p /tmp golden.XXXX)"
 # Expected outcome is a\nb\nc
-echo -ne "a\nb\nc" > "$expected_output_file"
+echo -ne "-keepclassmembers a b c\nfoobar\n-someflag 1 2 3" > "$expected_output_file"
 
 # Run the binary on the test data
 "$BINARY_UNDER_TEST" --input_json "$dummy_json_file" --output_file "$test_output_file"