also allow to configure node executable only

Author: simschla

lib/src/main/java/com/diffplug/spotless/npm/NodeExecutableResolver.java

@@ -42,4 +42,9 @@ static Optional<File> tryFindNextTo(File npmExecutable) {
 		}
 		return Optional.empty();
 	}
+
+	public static String explainMessage() {
+		return "Spotless was unable to find a node executable.\n" +
+				"Either specify the node executable explicitly or make sure it can be found next to the npm executable.";
+	}
 }

lib/src/main/java/com/diffplug/spotless/npm/NpmPathResolver.java

@@ -38,16 +38,45 @@ public NpmPathResolver(File explicitNpmExecutable, File explicitNodeExecutable,
 		this.additionalNpmrcLocations = Collections.unmodifiableList(new ArrayList<>(additionalNpmrcLocations));
 	}
 
+	/**
+	 * Finds the npm executable to use.
+	 * <br>
+	 * Either the explicit npm executable is returned, or - if an explicit node executable is configured - tries to find
+	 * the npm executable relative to the node executable.
+	 * Falls back to looking for npm on the user's system using {@link NpmExecutableResolver}
+	 *
+	 * @return the npm executable to use
+	 * @throws IllegalStateException if no npm executable could be found
+	 */
 	public File resolveNpmExecutable() {
-		return Optional.ofNullable(this.explicitNpmExecutable)
-				.orElseGet(() -> NpmExecutableResolver.tryFind()
-						.orElseThrow(() -> new IllegalStateException("Can't automatically determine npm executable and none was specifically supplied!\n\n" + NpmExecutableResolver.explainMessage())));
+		if (this.explicitNpmExecutable != null) {
+			return this.explicitNpmExecutable;
+		}
+		if (this.explicitNodeExecutable != null) {
+			File nodeExecutableCandidate = new File(this.explicitNodeExecutable.getParentFile(), NpmExecutableResolver.npmExecutableName());
+			if (nodeExecutableCandidate.canExecute()) {
+				return nodeExecutableCandidate;
+			}
+		}
+		return NpmExecutableResolver.tryFind()
+				.orElseThrow(() -> new IllegalStateException("Can't automatically determine npm executable and none was specifically supplied!\n\n" + NpmExecutableResolver.explainMessage()));
 	}
 
+	/**
+	 * Finds the node executable to use.
+	 * <br>
+	 * Either the explicit node executable is returned, or tries to find the node executable relative to the npm executable
+	 * found by {@link #resolveNpmExecutable()}.
+	 * @return the node executable to use
+	 * @throws IllegalStateException if no node executable could be found
+	 */
 	public File resolveNodeExecutable() {
-		return Optional.ofNullable(this.explicitNodeExecutable)
-				.orElseGet(() -> NodeExecutableResolver.tryFindNextTo(resolveNpmExecutable())
-						.orElseThrow(() -> new IllegalStateException("Can't automatically determine node executable and none was specifically supplied!\n\n" + NpmExecutableResolver.explainMessage())));
+		if (this.explicitNodeExecutable != null) {
+			return this.explicitNodeExecutable;
+		}
+		File npmExecutable = resolveNpmExecutable();
+		return NodeExecutableResolver.tryFindNextTo(npmExecutable)
+				.orElseThrow(() -> new IllegalStateException("Can't automatically determine node executable and none was specifically supplied!\n\n" + NodeExecutableResolver.explainMessage()));
 	}
 
 	public String resolveNpmrcContent() {

plugin-gradle/src/test/java/com/diffplug/gradle/spotless/NpmTestsWithoutNpmInstallationTest.java

@@ -92,4 +92,38 @@ void useNpmFromNodeGradlePlugin() throws Exception {
 		Assertions.assertThat(spotlessApply.getOutput()).contains("BUILD SUCCESSFUL");
 		assertFile("test.ts").sameAsResource("npm/prettier/config/typescript.configfile.clean");
 	}
+
+	@Test
+	void useNpmNextToConfiguredNodePluginFromNodeGradlePlugin() throws Exception {
+		setFile("build.gradle").toLines(
+				"plugins {",
+				"    id 'com.diffplug.spotless'",
+				"    id 'com.github.node-gradle.node' version '3.5.1'",
+				"}",
+				"repositories { mavenCentral() }",
+				"node {",
+				"    download = true",
+				"    version = '18.13.0'",
+				"    workDir = file(\"${buildDir}/nodejs\")",
+				"}",
+				"def prettierConfig = [:]",
+				"prettierConfig['printWidth'] = 50",
+				"prettierConfig['parser'] = 'typescript'",
+				"def nodeExecExtension = System.getProperty('os.name').toLowerCase().contains('windows') ? '.exe' : ''",
+				"spotless {",
+				"    format 'mytypescript', {",
+				"        target 'test.ts'",
+				"        prettier()",
+				"            .nodeExecutable(\"${tasks.named('nodeSetup').get().nodeDir.get()}/bin/node${nodeExecExtension}\")",
+				"            .config(prettierConfig)",
+				"    }",
+				"}");
+		setFile("test.ts").toResource("npm/prettier/config/typescript.dirty");
+		// make sure node binary is there
+		gradleRunner().withArguments("nodeSetup", "npmSetup").build();
+		// then run spotless using that node installation
+		final BuildResult spotlessApply = gradleRunner().withArguments("--stacktrace", "spotlessApply").build();
+		Assertions.assertThat(spotlessApply.getOutput()).contains("BUILD SUCCESSFUL");
+		assertFile("test.ts").sameAsResource("npm/prettier/config/typescript.configfile.clean");
+	}
 }