$ blaze config: add --output=json

This also generally refactors ConfigCommand to make a clean separation between
structural logic and output formatting logic.

ConfigCommand is responsible for taking a raw BuildConfiguration and translating it
into appropriate data structures that represent what it wants to output: what data
is output, how data relates to other data, and how results are ordered.

An output formatter then consumes these data structures to style the output
accordingly.

This also moves the logic that handled both out of BuildConfiguration & FragmentOptions.

It's neat how simple this makes JsonOutputFormatter. :)

Serves #10613.

PiperOrigin-RevId: 293152292

src/main/java/com/google/devtools/build/lib/BUILD

@@ -1320,6 +1320,7 @@ java_library(
         "//src/main/protobuf:test_status_java_proto",
         "//third_party:auto_value",
         "//third_party:flogger",
+        "//third_party:gson",
         "//third_party:guava",
         "//third_party:jsr305",
         "//third_party/protobuf:protobuf_java",

src/main/java/com/google/devtools/build/lib/analysis/config/BuildConfiguration.java

@@ -14,8 +14,6 @@
 
 package com.google.devtools.build.lib.analysis.config;
 
-import static java.util.Comparator.comparing;
-import static java.util.stream.Collectors.joining;
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Suppliers;
@@ -208,34 +206,6 @@ private int computeHashCode() {
     return Objects.hash(fragments, buildOptions.getNativeOptions());
   }
 
-  public void describe(StringBuilder sb) {
-    sb.append("BuildConfiguration ").append(checksum()).append(":\n");
-    // Fragments.
-    sb.append("  fragments: ")
-        .append(
-            getFragmentsMap().keySet().stream()
-                .sorted(comparing(Class::getName))
-                .map(Class::getName)
-                .collect(joining(",")))
-        .append("\n");
-    // Options.
-    getOptions().getFragmentClasses().stream()
-        .sorted(comparing(Class::getName))
-        .map(optionsClass -> getOptions().get(optionsClass))
-        .forEach(options -> options.describe(sb));
-    // User-defined options.
-    sb.append("Fragment user-defined {\n");
-    buildOptions.getStarlarkOptions().entrySet().stream()
-        .sorted(Comparator.comparing(Map.Entry::getKey))
-        .forEach(
-            entry ->
-                sb.append("  ")
-                    .append(entry.getKey().toString())
-                    .append(": ")
-                    .append(entry.getValue()));
-    sb.append("\n}");
-  }
-
   @Override
   public int hashCode() {
     return hashCode;

src/main/java/com/google/devtools/build/lib/analysis/config/FragmentOptions.java

@@ -14,7 +14,6 @@
 
 package com.google.devtools.build.lib.analysis.config;
 
-import static java.util.Map.Entry.comparingByKey;
 
 import com.google.common.collect.ImmutableMap;
 import com.google.devtools.common.options.OptionDefinition;
@@ -136,14 +135,4 @@ public String getErrorMessage() {
   public Map<OptionDefinition, SelectRestriction> getSelectRestrictions() {
     return ImmutableMap.of();
   }
-
-  public void describe(StringBuilder sb) {
-    sb.append("Fragment ").append(getClass().getName()).append(" {\n");
-    Map<String, Object> options = asMap();
-    options.entrySet().stream()
-        .sorted(comparingByKey())
-        .forEach(
-            e -> sb.append("  ").append(e.getKey()).append(": ").append(e.getValue()).append("\n"));
-    sb.append("}\n");
-  }
 }