Snippet generator mostly working, still needs some tweaks / bug fixes.

headless-services/bosh-language-server/src/main/java/org/springframework/ide/vscode/bosh/BoshDeploymentManifestSchema.java

@@ -25,13 +25,13 @@ import org.springframework.ide.vscode.bosh.models.ReleasesModel;
 import org.springframework.ide.vscode.bosh.models.StemcellData;
 import org.springframework.ide.vscode.bosh.models.StemcellModel;
 import org.springframework.ide.vscode.bosh.models.StemcellsModel;
+import org.springframework.ide.vscode.bosh.snippets.SchemaBasedSnippetGenerator;
 import org.springframework.ide.vscode.commons.util.Assert;
 import org.springframework.ide.vscode.commons.util.CollectorUtil;
 import org.springframework.ide.vscode.commons.util.PartialCollection;
 import org.springframework.ide.vscode.commons.util.Renderable;
 import org.springframework.ide.vscode.commons.util.Renderables;
 import org.springframework.ide.vscode.commons.util.StringUtil;
-import org.springframework.ide.vscode.commons.util.ValueParser;
 import org.springframework.ide.vscode.commons.util.ValueParsers;
 import org.springframework.ide.vscode.commons.yaml.ast.NodeUtil;
 import org.springframework.ide.vscode.commons.yaml.ast.YamlAstCache;
@@ -40,7 +40,6 @@ import org.springframework.ide.vscode.commons.yaml.path.YamlPath;
 import org.springframework.ide.vscode.commons.yaml.reconcile.ASTTypeCache;
 import org.springframework.ide.vscode.commons.yaml.reconcile.YamlSchemaProblems;
 import org.springframework.ide.vscode.commons.yaml.schema.DynamicSchemaContext;
-import org.springframework.ide.vscode.commons.yaml.schema.SchemaContextAware;
 import org.springframework.ide.vscode.commons.yaml.schema.YType;
 import org.springframework.ide.vscode.commons.yaml.schema.YTypeFactory;
 import org.springframework.ide.vscode.commons.yaml.schema.YTypeFactory.AbstractType;
@@ -53,7 +52,6 @@ import org.springframework.ide.vscode.commons.yaml.schema.YTypedProperty;
 import org.springframework.ide.vscode.commons.yaml.schema.YamlSchema;
 import org.springframework.ide.vscode.commons.yaml.schema.constraints.Constraints;
 
-import com.fasterxml.jackson.databind.type.TypeFactory;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableSet;
 
@@ -328,7 +326,6 @@ public class BoshDeploymentManifestSchema implements YamlSchema {
 		return new StemcellModel(path.dropLast().traverseToNode(ast));
 	}
 
-
 	private String getCurrentEntityProperty(DynamicSchemaContext dc, String propName) {
 		YamlPath path = dc.getPath();
 		YamlFileAST ast = asts.getSafeAst(dc.getDocument(), true);

headless-services/bosh-language-server/src/main/java/org/springframework/ide/vscode/bosh/BoshLanguageServer.java

@@ -14,6 +14,7 @@ import org.springframework.ide.vscode.bosh.models.CloudConfigModel;
 import org.springframework.ide.vscode.bosh.models.DynamicModelProvider;
 import org.springframework.ide.vscode.bosh.models.ReleasesModel;
 import org.springframework.ide.vscode.bosh.models.StemcellsModel;
+import org.springframework.ide.vscode.bosh.snippets.SchemaBasedSnippetGenerator;
 import org.springframework.ide.vscode.commons.languageserver.completion.VscodeCompletionEngineAdapter;
 import org.springframework.ide.vscode.commons.languageserver.hover.HoverInfoProvider;
 import org.springframework.ide.vscode.commons.languageserver.hover.VscodeHoverEngine;
@@ -23,7 +24,6 @@ import org.springframework.ide.vscode.commons.languageserver.util.Settings;
 import org.springframework.ide.vscode.commons.languageserver.util.SimpleLanguageServer;
 import org.springframework.ide.vscode.commons.languageserver.util.SimpleTextDocumentService;
 import org.springframework.ide.vscode.commons.languageserver.util.SimpleWorkspaceService;
-import org.springframework.ide.vscode.commons.util.Log;
 import org.springframework.ide.vscode.commons.util.text.LanguageId;
 import org.springframework.ide.vscode.commons.util.text.TextDocument;
 import org.springframework.ide.vscode.commons.yaml.ast.YamlAstCache;
@@ -41,6 +41,7 @@ import org.springframework.ide.vscode.commons.yaml.structure.YamlStructureProvid
 public class BoshLanguageServer extends SimpleLanguageServer {
 
 	private final VscodeCompletionEngineAdapter completionEngine;
+	private BoshDeploymentManifestSchema schema;
 
 	public BoshLanguageServer(BoshCliConfig cliConfig,
 			DynamicModelProvider<CloudConfigModel> cloudConfigProvider,
@@ -52,10 +53,11 @@ public class BoshLanguageServer extends SimpleLanguageServer {
 		SimpleTextDocumentService documents = getTextDocumentService();
 
 		ASTTypeCache astTypeCache = new ASTTypeCache();
-		BoshDeploymentManifestSchema schema = new BoshDeploymentManifestSchema(asts, astTypeCache, cloudConfigProvider, stemcellsProvider, releasesProvider);
+		schema = new BoshDeploymentManifestSchema(asts, astTypeCache, cloudConfigProvider, stemcellsProvider, releasesProvider);
 
 		YamlStructureProvider structureProvider = YamlStructureProvider.DEFAULT;
 		YamlAssistContextProvider contextProvider = new SchemaBasedYamlAssistContextProvider(schema);
+		enableSnippets(true);
 		YamlCompletionEngine yamlCompletionEngine = new YamlCompletionEngine(structureProvider, contextProvider, YamlCompletionEngineOptions.DEFAULT);
 		completionEngine = createCompletionEngineAdapter(this, yamlCompletionEngine);
 		HoverInfoProvider infoProvider = new YamlHoverInfoProvider(asts.getAstProvider(true), structureProvider, contextProvider);
@@ -87,6 +89,14 @@ public class BoshLanguageServer extends SimpleLanguageServer {
 		}
 	}
 
+	public void enableSnippets(boolean enable) {
+		if (enable) {
+			schema.f.setSnippetProvider(new SchemaBasedSnippetGenerator(schema.getTypeUtil(), this::createSnippetBuilder));
+		} else {
+			schema.f.setSnippetProvider(null);
+		}
+	}
+
 	public BoshLanguageServer setMaxCompletions(int maxCompletions) {
 		completionEngine.setMaxCompletions(maxCompletions);
 		return this;

headless-services/bosh-language-server/src/main/java/org/springframework/ide/vscode/bosh/snippets/SchemaBasedSnippetGenerator.java

@@ -0,0 +1,152 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.ide.vscode.bosh.snippets;
+
+import java.util.Collection;
+import java.util.List;
+import java.util.concurrent.ExecutionException;
+import java.util.stream.Collectors;
+
+import org.springframework.ide.vscode.commons.languageserver.util.SnippetBuilder;
+import org.springframework.ide.vscode.commons.util.Log;
+import org.springframework.ide.vscode.commons.yaml.schema.YType;
+import org.springframework.ide.vscode.commons.yaml.schema.YTypeUtil;
+import org.springframework.ide.vscode.commons.yaml.schema.YTypedProperty;
+import org.springframework.ide.vscode.commons.yaml.snippet.Snippet;
+import org.springframework.ide.vscode.commons.yaml.snippet.TypeBasedSnippetProvider;
+import org.springframework.ide.vscode.commons.yaml.util.YamlIndentUtil;
+
+import com.google.common.base.Supplier;
+import com.google.common.cache.Cache;
+import com.google.common.cache.CacheBuilder;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+
+/**
+ * An implementation of {@link TypeBasedSnippetProvider} that generates snippets
+ * automatically from schema types.
+ */
+public class SchemaBasedSnippetGenerator implements TypeBasedSnippetProvider {
+
+	private YTypeUtil typeUtil;
+	private Supplier<SnippetBuilder> snippetBuilderFactory;
+
+	public SchemaBasedSnippetGenerator(YTypeUtil typeUtil, Supplier<SnippetBuilder> snippetBuilderFactory) {
+		super();
+		this.typeUtil = typeUtil;
+		this.snippetBuilderFactory = snippetBuilderFactory;
+	}
+
+	private Cache<YType, Collection<Snippet>> cache = CacheBuilder.newBuilder().build();
+	private int maxNesting = Integer.MAX_VALUE;
+
+	@Override
+	public Collection<Snippet> getSnippets(YType type) {
+		try {
+			return cache.get(type, () -> generateSnippets(type));
+		} catch (ExecutionException e) {
+			Log.log(e);
+			return ImmutableList.of();
+		}
+	}
+
+	private Collection<Snippet> generateSnippets(YType type) {
+		ImmutableList.Builder<Snippet> snippets = ImmutableList.builder();
+		//Generate a 'full' snippet that defines all required properties of the current type.
+		Snippet snippet = generateFullSnippet(type, 0);
+		if (snippet!=null) {
+			snippets.add(snippet);
+		}
+		//Generate single property snippets that only define a single properties (with 'mega snippets' for nested types)
+		for (YTypedProperty p : typeUtil.getProperties(type)) {
+			String propName = p.getName();
+			SnippetBuilder builder = snippetBuilderFactory.get();
+			generateBeanSnippet(ImmutableList.of(p), builder, 0, maxNesting);
+			if (builder.getPlaceholderCount()>=2) {
+				snippets.add(new Snippet(p.getName()+" Snippet", builder.toString(), (dc) ->
+					!dc.getDefinedProperties().contains(propName)
+				));
+			}
+		}
+		return snippets.build();
+	}
+
+	private Snippet generateFullSnippet(YType type, int indent) {
+		if (typeUtil.isBean(type)) {
+			SnippetBuilder builder = snippetBuilderFactory.get();
+			List<YTypedProperty> requiredProps = typeUtil.getProperties(type).stream()
+			.filter(p -> p.isPrimary() || p.isRequired())
+			.collect(Collectors.toList());
+			if (!requiredProps.isEmpty()) {
+				generateBeanSnippet(requiredProps, builder, indent, maxNesting);
+			}
+			if (builder.getPlaceholderCount()>=2) {
+				//place holder count is a good indicator of snippet complexity and allows us to
+				// avoid creating trivial snippets (which aren't very useful).
+				ImmutableSet<YTypedProperty> vetoProps = ImmutableSet.copyOf(requiredProps);
+				// Do not suggest snippet if it contains properties that are already defined.
+				return new Snippet(typeUtil.niceTypeName(type)+" Snippet", builder.toString(), (dc) ->
+					dc.getDefinedProperties().stream().noneMatch(vetoProps::contains)
+				);
+			}
+		}
+		return null;
+	}
+
+	private void generateBeanSnippet(List<YTypedProperty> props, SnippetBuilder builder, int indent, int nestingLimit) {
+		if (nestingLimit>0) {
+			boolean first = true;
+			for (YTypedProperty p : props) {
+				if (!first) {
+					builder.newline(indent);
+				}
+				builder.text(p.getName());
+				builder.text(":");
+				generateNestedSnippet(false, p.getType(), builder, indent, nestingLimit-1);
+				first = false;
+			}
+		} else {
+			//reached the limit of bean number of nested property expansions allowed.
+			builder.placeHolder();
+		}
+	}
+
+
+	private void generateNestedSnippet(boolean parentIsSeq, YType type, SnippetBuilder builder, int indent, int nestingLimit) {
+		if (type==null) {
+			//Assume its some kind of pojo bean
+			builder.newline(indent+YamlIndentUtil.INDENT_BY);
+			builder.placeHolder();
+		} else if (typeUtil.isBean(type) || typeUtil.isMap(type)) {
+			if (!parentIsSeq) {
+				//ready to enter nested keys on next line
+				indent += YamlIndentUtil.INDENT_BY;
+				builder.newline(indent);
+			}
+			//Insert required keys
+			List<YTypedProperty> requiredProps = typeUtil.getProperties(type).stream()
+			.filter(p -> p.isPrimary() || p.isRequired())
+			.collect(Collectors.toList());
+			generateBeanSnippet(requiredProps, builder, indent, nestingLimit);
+		} else if (typeUtil.isSequencable(type)) {
+			//ready to enter sequence element on next line
+			builder.newline(indent);
+			builder.text("- ");
+			indent += YamlIndentUtil.INDENT_BY;
+			generateNestedSnippet(true, typeUtil.getDomainType(type), builder, indent, nestingLimit);
+		} else { //Treat like atomic
+			//ready to enter whatever on the same line
+			builder.text(" ");
+			builder.placeHolder();
+		}
+	}
+
+}

headless-services/bosh-language-server/src/test/java/org/springframework/ide/vscode/bosh/BoshEditorTest.java

@@ -45,7 +45,7 @@ import com.google.common.collect.ImmutableSet;
 
 public class BoshEditorTest {
 
-	LanguageServerHarness harness;
+	LanguageServerHarness<BoshLanguageServer> harness;
 
 	private BoshCliConfig cliConfig = new BoshCliConfig();
 	private MockCloudConfigProvider cloudConfigProvider = new MockCloudConfigProvider(cliConfig);
@@ -53,7 +53,7 @@ public class BoshEditorTest {
 	private DynamicModelProvider<ReleasesModel> releasesProvider = mock(DynamicModelProvider.class);
 
 	@Before public void setup() throws Exception {
-		harness = new LanguageServerHarness(() -> {
+		harness = new LanguageServerHarness<BoshLanguageServer>(() -> {
 				return new BoshLanguageServer(cliConfig, cloudConfigProvider,
 						(dc) -> stemcellsProvider.getModel(dc),
 						(dc) -> releasesProvider.getModel(dc)
@@ -156,6 +156,7 @@ public class BoshEditorTest {
 	}
 
 	@Test public void toplevelPropertyCompletions() throws Exception {
+		harness.getServer().enableSnippets(false);
 		Editor editor = harness.newEditor(
 				"<*>"
 		);
@@ -200,6 +201,7 @@ public class BoshEditorTest {
 	}
 
 	@Test public void stemcellCompletions() throws Exception {
+		harness.getServer().enableSnippets(false);
 		Editor editor = harness.newEditor(
 				"stemcells:\n" +
 				"- <*>"
@@ -253,6 +255,7 @@ public class BoshEditorTest {
 
 
 	@Test public void releasesBlockCompletions() throws Exception {
+		harness.getServer().enableSnippets(false);
 		Editor editor = harness.newEditor(
 				"releases:\n" +
 				"- <*>"
@@ -518,6 +521,7 @@ public class BoshEditorTest {
 	}
 
 	@Test public void updateBlockCompletions() throws Exception {
+		harness.getServer().enableSnippets(false);
 		Editor editor = harness.newEditor(
 				"update:\n" +
 				"  <*>"
@@ -557,6 +561,7 @@ public class BoshEditorTest {
 	}
 
 	@Test public void variablesBlockCompletions() throws Exception {
+		harness.getServer().enableSnippets(false);
 		Editor editor = harness.newEditor(
 				"variables:\n" +
 				"- <*>"

headless-services/bosh-language-server/src/test/java/org/springframework/ide/vscode/bosh/SchemaBasedSnippetGeneratorTest.java

@@ -0,0 +1,36 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.ide.vscode.bosh;
+
+import org.junit.Test;
+import org.springframework.ide.vscode.bosh.snippets.SchemaBasedSnippetGenerator;
+import org.springframework.ide.vscode.commons.languageserver.util.SnippetBuilder;
+import org.springframework.ide.vscode.commons.yaml.ast.YamlAstCache;
+import org.springframework.ide.vscode.commons.yaml.reconcile.ASTTypeCache;
+import org.springframework.ide.vscode.commons.yaml.schema.DynamicSchemaContext;
+import org.springframework.ide.vscode.commons.yaml.schema.YType;
+import org.springframework.ide.vscode.commons.yaml.schema.YTypeUtil;
+
+public class SchemaBasedSnippetGeneratorTest {
+
+	private ASTTypeCache astTypes = new ASTTypeCache();
+	private YamlAstCache asts = new YamlAstCache();
+	private BoshDeploymentManifestSchema schema = new BoshDeploymentManifestSchema(asts, astTypes, (dc) -> null, (dc) -> null, (dc) -> null);
+	private YTypeUtil typeUtil = schema.getTypeUtil();
+	private SchemaBasedSnippetGenerator generator = new SchemaBasedSnippetGenerator(typeUtil, SnippetBuilder::new);
+
+	@Test
+	public void toplevelSnippet() throws Exception {
+		YType v2Schema = typeUtil.inferMoreSpecificType(schema.getTopLevelType(), DynamicSchemaContext.NULL);
+		System.out.println(generator.getSnippets(v2Schema).iterator().next());
+	}
+
+}

headless-services/commons/commons-language-server/src/main/java/org/springframework/ide/vscode/commons/languageserver/util/SnippetBuilder.java

@@ -35,11 +35,7 @@ public class SnippetBuilder {
 	 * be overridden by subclasses to support other formats.
 	 * <p>
 	 * The default implementation creates place holder strings that
-	 * match the undocumented format vscode currently supports.
-	 * <p>
-	 * Note: this format is explicitly different from what the LSP
-	 * specifies. So it is very likely we should change this implementation
-	 * in the near future.
+	 * match format specified by LSP 3.0.
 	 */
 	protected String createPlaceHolder(int id) {
 		return "$"+id;
@@ -50,4 +46,24 @@ public class SnippetBuilder {
 		return buf.toString();
 	}
 
+	public void newline(int indent) {
+		buf.append("\n");
+		for (int i = 0; i < indent; i++) {
+			buf.append(' ');
+		}
+	}
+
+	public void ensureSpace() {
+		if (buf.length()>0 && !Character.isWhitespace(buf.charAt(buf.length()-1))) {
+			buf.append(' ');
+		}
+	}
+
+	/**
+	 * @return The number of placeholder that where inserted in the snippet.
+	 */
+	public int getPlaceholderCount() {
+		return nextPlaceHolderId-1;
+	}
+
 }

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/completion/YTypeAssistContext.java

@@ -45,6 +45,8 @@ import org.springframework.ide.vscode.commons.yaml.schema.YType;
 import org.springframework.ide.vscode.commons.yaml.schema.YTypeUtil;
 import org.springframework.ide.vscode.commons.yaml.schema.YTypedProperty;
 import org.springframework.ide.vscode.commons.yaml.schema.YValueHint;
+import org.springframework.ide.vscode.commons.yaml.snippet.Snippet;
+import org.springframework.ide.vscode.commons.yaml.snippet.TypeBasedSnippetProvider;
 import org.springframework.ide.vscode.commons.yaml.structure.YamlDocument;
 import org.springframework.ide.vscode.commons.yaml.structure.YamlStructureParser.SNode;
 import org.springframework.ide.vscode.commons.yaml.util.YamlIndentUtil;
@@ -98,6 +100,29 @@ public class YTypeAssistContext extends AbstractYamlAssistContext {
 		List<ICompletionProposal> completions = getValueCompletions(doc, node, offset, query);
 		if (completions.isEmpty()) {
 			completions = getKeyCompletions(doc, offset, query);
+			TypeBasedSnippetProvider snippetProvider = typeUtil.getSnippetProvider();
+			if (snippetProvider!=null) {
+				Collection<Snippet> snippets = snippetProvider.getSnippets(type);
+				YamlIndentUtil indenter = new YamlIndentUtil(doc);
+				for (Snippet snippet : snippets) {
+					String snippetName = snippet.getName();
+					double score = FuzzyMatcher.matchScore(query, snippetName);
+					if (score!=0.0) {
+						String textBeforeQuery = doc.getLineTextBefore(offset);
+						DocumentEdits edits = new DocumentEdits(doc.getDocument());
+						int start = offset - query.length();
+						edits.delete(start, query);
+						int referenceIndent = textBeforeQuery.length();
+						boolean needsSpace = start > 0 && !Character.isWhitespace(doc.getChar(offset-1));
+						if (needsSpace) {
+							referenceIndent++;
+							edits.insert(start, " ");
+						}
+						edits.insert(start, indenter.applyIndentation(snippet.getSnippet(), referenceIndent));
+						completions.add(completionFactory().valueProposal(snippetName, query, snippetName, type, null, score, edits, typeUtil));
+					}
+				}
+			}
 		}
 		if (typeUtil.isSequencable(type)) {
 			completions = new ArrayList<>(completions);

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/completion/YamlCompletionEngineOptions.java

@@ -13,15 +13,15 @@ package org.springframework.ide.vscode.commons.yaml.completion;
 public interface YamlCompletionEngineOptions {
 	/**
 	 * Whether the completion engine includes 'less indented' proposals (i.e. proposals
-	 * that aren't valid at the current CA position, but are valid if we delete 
-	 * some spaces in front of the cursor first. 
+	 * that aren't valid at the current CA position, but are valid if we delete
+	 * some spaces in front of the cursor first.
 	 */
-	default boolean includeDeindentedProposals() { 
+	default boolean includeDeindentedProposals() {
 		//Disabled by default for now because of bug introduced in VSCode 1.12:
 		//https://github.com/Microsoft/vscode/issues/26096
 		return true;
 	}
-	
+
 	YamlCompletionEngineOptions DEFAULT = new YamlCompletionEngineOptions() {};
 	YamlCompletionEngineOptions TEST_DEFAULT = new YamlCompletionEngineOptions() {
 		@Override public boolean includeDeindentedProposals() { return true; }

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/schema/YTypeFactory.java

@@ -16,7 +16,6 @@ import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.LinkedHashMap;
-import java.util.LinkedHashSet;
 import java.util.List;
 import java.util.Map;
 import java.util.Map.Entry;
@@ -31,8 +30,6 @@ import org.springframework.ide.vscode.commons.languageserver.reconcile.Replaceme
 import org.springframework.ide.vscode.commons.util.Assert;
 import org.springframework.ide.vscode.commons.util.CollectorUtil;
 import org.springframework.ide.vscode.commons.util.EnumValueParser;
-import org.springframework.ide.vscode.commons.util.ExceptionUtil;
-import org.springframework.ide.vscode.commons.util.Log;
 import org.springframework.ide.vscode.commons.util.PartialCollection;
 import org.springframework.ide.vscode.commons.util.Renderable;
 import org.springframework.ide.vscode.commons.util.Renderables;
@@ -40,8 +37,8 @@ import org.springframework.ide.vscode.commons.util.ValueParser;
 import org.springframework.ide.vscode.commons.yaml.reconcile.YamlSchemaProblems;
 import org.springframework.ide.vscode.commons.yaml.schema.constraints.Constraint;
 import org.springframework.ide.vscode.commons.yaml.schema.constraints.Constraints;
+import org.springframework.ide.vscode.commons.yaml.snippet.TypeBasedSnippetProvider;
 
-import com.google.common.base.Function;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableList.Builder;
 import com.google.common.collect.ImmutableMap;
@@ -60,6 +57,7 @@ public class YTypeFactory {
 
 	private boolean enableTieredOptionalPropertyProposals = true;
 	private boolean suggestDeprecatedProperties = true;
+	private TypeBasedSnippetProvider snippetProvider = null;
 
 	private static class Deprecation {
 		final String errorMsg;
@@ -239,6 +237,11 @@ public class YTypeFactory {
 			return ((AbstractType)type).getCustomContentAssistant();
 		}
 
+		@Override
+		public TypeBasedSnippetProvider getSnippetProvider() {
+			return snippetProvider;
+		}
+
 		@Override
 		public boolean tieredOptionalPropertyProposals() {
 			return enableTieredOptionalPropertyProposals;
@@ -980,5 +983,10 @@ public class YTypeFactory {
 		return this;
 	}
 
+	public YTypeFactory setSnippetProvider(TypeBasedSnippetProvider snippetProvider) {
+		this.snippetProvider = snippetProvider;
+		return this;
+	}
+
 
 }

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/schema/YTypeUtil.java

@@ -10,12 +10,15 @@
  *******************************************************************************/
 package org.springframework.ide.vscode.commons.yaml.schema;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 
 import org.springframework.ide.vscode.commons.util.PartialCollection;
 import org.springframework.ide.vscode.commons.util.ValueParser;
 import org.springframework.ide.vscode.commons.yaml.schema.constraints.Constraint;
+import org.springframework.ide.vscode.commons.yaml.snippet.Snippet;
+import org.springframework.ide.vscode.commons.yaml.snippet.TypeBasedSnippetProvider;
 
 /**
  * An implementation of YTypeUtil provides implementations of various
@@ -51,6 +54,14 @@ public interface YTypeUtil {
 
 	ISubCompletionEngine getCustomContentAssistant(YType type);
 
+	/**
+	 * Config option for type-bases complection enging. Snippets can be
+	 * associated with schema types. These snippets will be suggested as
+	 * additional completions based on the type of value expected in
+	 * a context.
+	 */
+	TypeBasedSnippetProvider getSnippetProvider();
+
 	/**
 	 * Config option for type-based completion engine. This enables the
 	 * 'tiered' proposals feature (so that optional properties are not

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/snippet/Snippet.java

@@ -0,0 +1,40 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.ide.vscode.commons.yaml.snippet;
+
+import java.util.function.Predicate;
+
+import org.springframework.ide.vscode.commons.yaml.schema.DynamicSchemaContext;
+
+public class Snippet {
+
+	private final String name;
+	private final String snippet;
+	private final Predicate<DynamicSchemaContext> applicability;
+
+	public Snippet(String name, String snippet, Predicate<DynamicSchemaContext> applicability) {
+		super();
+		this.name = name;
+		this.snippet = snippet;
+		this.applicability = applicability;
+	}
+	public String getName() {
+		return name;
+	}
+	public String getSnippet() {
+		return snippet;
+	}
+
+	@Override
+	public String toString() {
+		return "Snippet [ name="+name+",\n" +snippet +"\n]";
+	}
+}

headless-services/commons/commons-yaml/src/main/java/org/springframework/ide/vscode/commons/yaml/snippet/TypeBasedSnippetProvider.java

@@ -0,0 +1,21 @@
+/*******************************************************************************
+ * Copyright (c) 2017 Pivotal, Inc.
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/epl-v10.html
+ *
+ * Contributors:
+ *     Pivotal, Inc. - initial API and implementation
+ *******************************************************************************/
+package org.springframework.ide.vscode.commons.yaml.snippet;
+
+import java.util.Collection;
+
+import org.springframework.ide.vscode.commons.yaml.schema.YType;
+
+public interface TypeBasedSnippetProvider {
+
+	Collection<Snippet> getSnippets(YType contextType);
+
+}

headless-services/commons/language-server-test-harness/src/main/java/org/springframework/ide/vscode/languageserver/testharness/LanguageServerHarness.java

@@ -92,16 +92,16 @@ import com.google.common.collect.ImmutableList;
 
 import reactor.core.publisher.Mono;
 
-public class LanguageServerHarness {
+public class LanguageServerHarness<S extends SimpleLanguageServer> {
 
 	//Warning this 'harness' is incomplete. Growing it as needed.
 
 	private Random random = new Random();
 
-	private Callable<? extends SimpleLanguageServer> factory;
+	private Callable<S> factory;
 	private LanguageId defaultLanguageId;
 
-	private SimpleLanguageServer server;
+	private S server;
 
 	private InitializeResult initResult;
 
@@ -110,12 +110,12 @@ public class LanguageServerHarness {
 	private List<Editor> activeEditors = new ArrayList<>();
 
 
-	public LanguageServerHarness(Callable<? extends SimpleLanguageServer> factory, LanguageId defaultLanguageId) {
+	public LanguageServerHarness(Callable<S> factory, LanguageId defaultLanguageId) {
 		this.factory = factory;
 		this.defaultLanguageId = defaultLanguageId;
 	}
 
-	public LanguageServerHarness(Callable<? extends SimpleLanguageServer> factory) throws Exception {
+	public LanguageServerHarness(Callable<S> factory) throws Exception {
 		this(factory, LanguageId.PLAINTEXT);
 	}
 
@@ -184,9 +184,9 @@ public class LanguageServerHarness {
 		workspaceCap.setExecuteCommand(exeCap);
 		clientCap.setWorkspace(workspaceCap);
 		initParams.setCapabilities(clientCap);
-		initResult = server.initialize(initParams).get();
-		if (server instanceof LanguageClientAware) {
-			((LanguageClientAware) server).connect(new STS4LanguageClient() {
+		initResult = getServer().initialize(initParams).get();
+		if (getServer() instanceof LanguageClientAware) {
+			((LanguageClientAware) getServer()).connect(new STS4LanguageClient() {
 				@Override
 				public void telemetryEvent(Object object) {
 					// TODO Auto-generated method stub
@@ -248,15 +248,15 @@ public class LanguageServerHarness {
 			});
 
 		}
-		server.initialized();
+		getServer().initialized();
 		return initResult;
 	}
 
 	public TextDocumentInfo openDocument(TextDocumentInfo documentInfo) throws Exception {
 		DidOpenTextDocumentParams didOpen = new DidOpenTextDocumentParams();
 		didOpen.setTextDocument(documentInfo.getDocument());
-		if (server!=null) {
-			server.getTextDocumentService().didOpen(didOpen);
+		if (getServer()!=null) {
+			getServer().getTextDocumentService().didOpen(didOpen);
 		}
 		return documentInfo;
 	}
@@ -295,8 +295,8 @@ public class LanguageServerHarness {
 		default:
 			throw new IllegalStateException("Unkown SYNC mode: "+getDocumentSyncMode());
 		}
-		if (server!=null) {
-			server.getTextDocumentService().didChange(didChange);
+		if (getServer()!=null) {
+			getServer().getTextDocumentService().didChange(didChange);
 		}
 		return documents.get(uri);
 	}
@@ -320,8 +320,8 @@ public class LanguageServerHarness {
 		default:
 			throw new IllegalStateException("Unkown SYNC mode: "+getDocumentSyncMode());
 		}
-		if (server!=null) {
-			server.getTextDocumentService().didChange(didChange);
+		if (getServer()!=null) {
+			getServer().getTextDocumentService().didChange(didChange);
 		}
 		return documents.get(uri);
 	}
@@ -339,7 +339,7 @@ public class LanguageServerHarness {
 	}
 
 	public PublishDiagnosticsParams getDiagnostics(TextDocumentInfo doc) throws Exception {
-		this.server.waitForReconcile();
+		this.getServer().waitForReconcile();
 		return diagnostics.get(doc.getUri());
 	}
 
@@ -376,8 +376,8 @@ public class LanguageServerHarness {
 		TextDocumentPositionParams params = new TextDocumentPositionParams();
 		params.setPosition(cursor);
 		params.setTextDocument(doc.getId());
-		server.waitForReconcile();
-		Either<List<CompletionItem>, CompletionList> completions = server.getTextDocumentService().completion(params).get();
+		getServer().waitForReconcile();
+		Either<List<CompletionItem>, CompletionList> completions = getServer().getTextDocumentService().completion(params).get();
 		if (completions.isLeft()) {
 			List<CompletionItem> list = completions.getLeft();
 			return new CompletionList(false, list);
@@ -391,14 +391,14 @@ public class LanguageServerHarness {
 		TextDocumentPositionParams params = new TextDocumentPositionParams();
 		params.setPosition(cursor);
 		params.setTextDocument(document.getId());
-		return server.getTextDocumentService().hover(params ).get();
+		return getServer().getTextDocumentService().hover(params ).get();
 	}
 
 
 	public CompletionItem resolveCompletionItem(CompletionItem maybeUnresolved) {
-		if (server.hasLazyCompletionResolver()) {
+		if (getServer().hasLazyCompletionResolver()) {
 			try {
-				return server.getTextDocumentService().resolveCompletionItem(maybeUnresolved).get();
+				return getServer().getTextDocumentService().resolveCompletionItem(maybeUnresolved).get();
 			} catch (Exception e) {
 				throw new RuntimeException(e);
 			}
@@ -477,14 +477,14 @@ public class LanguageServerHarness {
 	}
 
 	public List<? extends Location> getDefinitions(TextDocumentPositionParams params) throws Exception {
-		server.waitForReconcile(); //goto definitions relies on reconciler infos! Must wait or race condition breaking tests occasionally.
-		return server.getTextDocumentService().definition(params).get();
+		getServer().waitForReconcile(); //goto definitions relies on reconciler infos! Must wait or race condition breaking tests occasionally.
+		return getServer().getTextDocumentService().definition(params).get();
 	}
 
 	public List<CodeAction> getCodeActions(TextDocumentInfo doc, Diagnostic problem) throws Exception {
 		CodeActionContext context = new CodeActionContext(ImmutableList.of(problem));
 		List<? extends Command> actions =
-				server.getTextDocumentService().codeAction(new CodeActionParams(doc.getId(), problem.getRange(), context)).get();
+				getServer().getTextDocumentService().codeAction(new CodeActionParams(doc.getId(), problem.getRange(), context)).get();
 		return actions.stream()
 				.map((command) -> new CodeAction(this, command))
 				.collect(Collectors.toList());
@@ -498,7 +498,7 @@ public class LanguageServerHarness {
 		//Note convert the params to a 'typeless' Object because that is more representative on how it will be
 		// received when we get it in a real client/server setting (i.e. parsed from json).
 		List untypedParams = mapper.convertValue(args, List.class);
-		server.getWorkspaceService()
+		getServer().getWorkspaceService()
 			.executeCommand(new ExecuteCommandParams(command.getCommand(), untypedParams))
 			.get();
 	}
@@ -544,9 +544,9 @@ public class LanguageServerHarness {
 	}
 
 	public List<? extends SymbolInformation> getDocumentSymbols(TextDocumentInfo document) throws Exception {
-		server.waitForReconcile(); //TODO: if the server works properly this shouldn't be needed it should do that internally itself somehow.
+		getServer().waitForReconcile(); //TODO: if the server works properly this shouldn't be needed it should do that internally itself somehow.
 		DocumentSymbolParams params = new DocumentSymbolParams(document.getId());
-		return server.getTextDocumentService().documentSymbol(params).get();
+		return getServer().getTextDocumentService().documentSymbol(params).get();
 	}
 
 	/**
@@ -554,7 +554,7 @@ public class LanguageServerHarness {
 	 */
 	public SynchronizationPoint reconcilerThreadStart() {
 		CompletableFuture<Void> blocker = new CompletableFuture<>();
-		server.setTestListener(new LanguageServerTestListener() {
+		getServer().setTestListener(new LanguageServerTestListener() {
 			@Override
 			public void reconcileStarted(String uri, int version) {
 				try {
@@ -585,4 +585,8 @@ public class LanguageServerHarness {
 			return newEditor(IOUtil.toString(is));
 		}
 	}
+
+	public S getServer() {
+		return server;
+	}
 }