Fleshing out docs for config-based modules (#6036)

Adds `Testing`, `Linting`, and `Example Web Project` and sections for
Java/Scala/Kotlin. These mostly mirror the top-level pages for each
language, and each gives a summary of performing each task with Mill's
config-based module definitions while delegating further reading to
their respective dedicated pages

Author: lihaoyi

.editorconfig

@@ -21,6 +21,9 @@ ktlint_standard_no-wildcard-imports = disabled
 [example/kotlinlib/linting/**/*]
 ktlint = disabled
 
+[example/kotlinlib/config/3-linting/**/*]
+ktlint = disabled
+
 [kotlinlib/test/resources/contrib/ktfmt/**/*]
 ktlint = disabled
 

.scalafmt.conf

@@ -26,6 +26,7 @@ project {
     "glob:**/mill/out/**",
     # don't try to format files that are purposefully malformed / misformatted
     "glob:**/example/scalalib/linting/1-scalafmt/src/Foo.scala",
+    "glob:**/example/scalalib/config/3-linting/src/Foo.scala",
     "glob:**/example/**/*-spotless*/**",
     "glob:**/javalib/test/resources/checkstyle/**",
     "glob:**/init/test/resources/giter8/hello.g8/src/main/g8/build.mill",

example/javalib/config/2-testing/build.mill

@@ -0,0 +1,16 @@
+//// SNIPPET:USAGE
+/** Usage
+
+> ./mill '{test,integration}' # run both test suites
+Test qux.QuxTests#hello() finished...
+Test qux.QuxTests#world() finished...
+Test qux.QuxIntegrationTests#helloworld() finished...
+
+> ./mill __.integration # run all integration test suites
+
+> ./mill __.test # run all normal test suites
+
+> ./mill __.testForked # run all test suites of any kind
+
+*/
+//// SNIPPET:TEST

example/javalib/config/2-testing/build.mill.yaml

@@ -0,0 +1,2 @@
+extends: [mill.javalib.JavaModule]
+

example/javalib/config/2-testing/integration/package.mill.yaml

@@ -0,0 +1,3 @@
+extends: [build.JavaTests, mill.javalib.TestModule.Junit5]
+mvnDeps: [org.junit.jupiter:junit-jupiter:5.8.2]
+moduleDeps: [test]

example/javalib/config/2-testing/integration/src/qux/QuxIntegrationTests.java

@@ -0,0 +1,13 @@
+package qux;
+
+import org.junit.jupiter.api.Test;
+
+public class QuxIntegrationTests {
+
+  @Test
+  public void helloworld() {
+    String result = Qux.hello();
+    QuxTests.assertHello(result);
+    QuxTests.assertWorld(result);
+  }
+}

example/javalib/config/2-testing/src/qux/Qux.java

@@ -0,0 +1,11 @@
+package qux;
+
+public class Qux {
+  public static void main(String[] args) {
+    System.out.println(hello());
+  }
+
+  public static String hello() {
+    return "Hello World";
+  }
+}

example/javalib/config/2-testing/test/package.mill.yaml

@@ -0,0 +1,2 @@
+extends: [build.JavaTests, mill.javalib.TestModule.Junit5]
+mvnDeps: [org.junit.jupiter:junit-jupiter:5.8.2]

example/javalib/config/2-testing/test/src/qux/QuxTests.java

@@ -0,0 +1,28 @@
+package qux;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+public class QuxTests {
+
+  public static void assertHello(String result) {
+    assertTrue(result.startsWith("Hello"));
+  }
+
+  public static void assertWorld(String result) {
+    assertTrue(result.endsWith("World"));
+  }
+
+  @Test
+  public void hello() {
+    String result = Qux.hello();
+    assertHello(result);
+  }
+
+  @Test
+  public void world() {
+    String result = Qux.hello();
+    assertWorld(result);
+  }
+}

example/javalib/config/3-linting/build.mill

@@ -0,0 +1,60 @@
+//// SNIPPET:LINT
+// === Autoformatting
+//
+// To autoformat your Java code with
+// https://github.com/palantir/palantir-java-format[Palantir Java Format], you
+// can run `./mill mill.javalib.palantirformat/` as shown below:
+
+/** Usage
+
+> cat src/foo/Foo.java
+package foo;
+public class Foo {
+public static void main(String[] args) {
+System.out.println("Hello World");
+new java.util.HashSet<Short>().remove(1);
+}
+}
+
+> ./mill mill.javalib.palantirformat/
+formatting 1 java sources ...
+
+> cat src/foo/Foo.java
+package foo;
+public class Foo {
+  public static void main(String[] args) {
+    System.out.println("Hello World");
+    new java.util.HashSet<Short>().remove(1);
+  }
+}
+
+*/
+
+// See xref:javalib/linting.adoc#_autoformatting_with_palantir_java_format[Autoformatting with Palantir Java Format] for more information.
+// Apart from Palantir Format, Mill also comes with
+// xref:javalib/linting.adoc#_auto_formatting_with_spotless[mill.javalib.spotless.SpotlessModule]
+// that can also be used
+
+// === Autofixing
+
+// To lint your code with https://errorprone.info/index[ErrorProne], you can
+// make yor module extend `mill.javalib.errorprone.ErrorProneModule`, which will
+// run errorprone lint checks every time you `compile` that module.
+
+/** See Also: build.mill.yaml */
+/** Usage
+
+> ./mill compile
+.../src/foo/Foo.java:6:42: [CollectionIncompatibleType]...
+...Argument '1' should not be passed to this method...
+...its type int is not compatible with its collection's type argument Short
+[warn]     (see https://errorprone.info/bugpattern/CollectionIncompatibleType)
+[warn] new java.util.HashSet<Short>().remove(1)
+[warn]                                         ^
+
+*/
+
+// See xref:javalib/linting.adoc#_linting_with_errorprone[Linting with ErrorProne] for more
+// details on how ErrorProne can be configured. Apart from ErrorProne, Mill also comes with
+// xref:javalib/linting.adoc#_linting_with_checkstyle[mill.contrib.checkstyle.CheckstyleModule] and
+// xref:javalib/linting.adoc#_static_analysis_with_pmd[mill.javalib.pmd.PmdModule]