Add navigation/find usages/completion support for Nix paths

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 ### Added
+- Navigation (Ctrl-B/Cmd-B) for Nix paths and path-like strings.
+    - Directories containing a `default.nix` file offer that file as an optional destination.
+- Find usages for files and directories in project view referenced by Nix paths.
+- Completion of files and subdirectories for Nix paths.
 
 ### Changed
 

src/main/java/org/nixos/idea/psi/impl/NixLiteralReferencingElementImpl.java

@@ -0,0 +1,22 @@
+package org.nixos.idea.psi.impl;
+
+import com.intellij.lang.ASTNode;
+import com.intellij.psi.PsiReference;
+import org.jetbrains.annotations.NotNull;
+import org.nixos.idea.reference.ReferenceUtil;
+
+public class NixLiteralReferencingElementImpl extends NixExprSimpleImpl {
+    public NixLiteralReferencingElementImpl(@NotNull ASTNode node) {
+        super(node);
+    }
+
+    @Override
+    public PsiReference @NotNull [] getReferences() {
+        return ReferenceUtil.getReferences(this);
+    }
+
+    @Override
+    public PsiReference getReference() {
+        return ReferenceUtil.getReference(this);
+    }
+}

src/main/java/org/nixos/idea/psi/impl/NixStringReferencingElementImpl.java

@@ -0,0 +1,22 @@
+package org.nixos.idea.psi.impl;
+
+import com.intellij.lang.ASTNode;
+import com.intellij.psi.PsiReference;
+import org.jetbrains.annotations.NotNull;
+import org.nixos.idea.reference.ReferenceUtil;
+
+public class NixStringReferencingElementImpl extends NixStringPartImpl {
+    public NixStringReferencingElementImpl(@NotNull ASTNode node) {
+        super(node);
+    }
+
+    @Override
+    public PsiReference @NotNull [] getReferences() {
+        return ReferenceUtil.getReferences(this);
+    }
+
+    @Override
+    public PsiReference getReference() {
+        return ReferenceUtil.getReference(this);
+    }
+}

src/main/java/org/nixos/idea/reference/NixReferenceContributor.java

@@ -0,0 +1,53 @@
+package org.nixos.idea.reference;
+
+import com.intellij.psi.*;
+import com.intellij.psi.impl.source.resolve.reference.impl.providers.FileReference;
+import com.intellij.psi.impl.source.resolve.reference.impl.providers.FileReferenceSet;
+import com.intellij.util.ProcessingContext;
+import org.jetbrains.annotations.NotNull;
+import org.nixos.idea.psi.NixLiteral;
+import org.nixos.idea.psi.NixStringText;
+
+import java.util.Arrays;
+
+import static com.intellij.patterns.PlatformPatterns.psiElement;
+import static com.intellij.patterns.StandardPatterns.or;
+import static com.intellij.patterns.StandardPatterns.string;
+
+public class NixReferenceContributor extends PsiReferenceContributor {
+
+    // Same as the pattern in Nix.flex.
+    private static final String NIX_PATH_REGEX = "[a-zA-Z0-9._+-]*(\\/[a-zA-Z0-9._+-]+)+\\/?";
+
+    @Override
+    public void registerReferenceProviders(@NotNull PsiReferenceRegistrar psiReferenceRegistrar) {
+        psiReferenceRegistrar.registerReferenceProvider(
+                or(
+                        psiElement(NixLiteral.class),
+                        psiElement(NixStringText.class)
+                                .withText(string().matches(NIX_PATH_REGEX))
+                ),
+                new NixReferenceProvider()
+        );
+    }
+
+    private static class NixReferenceProvider extends PsiReferenceProvider {
+
+        @Override
+        public boolean acceptsTarget(@NotNull PsiElement target) {
+            return target instanceof PsiFileSystemItem;
+        }
+
+        @Override
+        public PsiReference @NotNull [] getReferencesByElement(@NotNull PsiElement psiElement,
+                                                               @NotNull ProcessingContext processingContext) {
+            FileReferenceSet fileReferenceSet = new FileReferenceSet(psiElement);
+            FileReference[] references = fileReferenceSet.getAllReferences();
+            FileReference lastReference = fileReferenceSet.getLastReference();
+            FileReference defaultNixReference = fileReferenceSet.createFileReference(lastReference.getRangeInElement(), lastReference.getIndex() + 1, "default.nix");
+            PsiReference[] allReferences = Arrays.copyOf(references, references.length + 1);
+            allReferences[allReferences.length - 1] = defaultNixReference;
+            return allReferences;
+        }
+    }
+}

src/main/java/org/nixos/idea/reference/ReferenceUtil.java

@@ -0,0 +1,18 @@
+package org.nixos.idea.reference;
+
+import com.intellij.psi.PsiElement;
+import com.intellij.psi.PsiReference;
+import com.intellij.psi.PsiReferenceService;
+import com.intellij.psi.impl.source.resolve.reference.ReferenceProvidersRegistry;
+import com.intellij.util.ArrayUtil;
+import org.jetbrains.annotations.NotNull;
+
+public class ReferenceUtil {
+    public static PsiReference @NotNull [] getReferences(@NotNull PsiElement element) {
+        return ReferenceProvidersRegistry.getReferencesFromProviders(element, PsiReferenceService.Hints.NO_HINTS);
+    }
+
+    public static PsiReference getReference(@NotNull PsiElement element) {
+        return ArrayUtil.getFirstElement(getReferences(element));
+    }
+}

src/main/lang/Nix.bnf

@@ -169,6 +169,9 @@ expr_simple ::=
   | legacy_let
 identifier ::= ID
 literal ::= INT | FLOAT | PATH | HPATH | SPATH | URI
+{
+  mixin="org.nixos.idea.psi.impl.NixLiteralReferencingElementImpl"
+}
 parens ::= LPAREN expr recover_parens RPAREN { pin=1 }
 set ::= [ REC ] LCURLY recover_set (bind recover_set)* RCURLY { pin=2 }
 list ::= LBRAC recover_list (expr_select recover_list)* RBRAC { pin=1 }
@@ -186,6 +189,9 @@ ind_string ::= IND_STRING_OPEN string_part* IND_STRING_CLOSE { pin=1 }
 ;{ extends("string_text|antiquotation")=string_part }
 string_part ::= string_text | antiquotation { recoverWhile=string_part_recover }
 string_text ::= STR | IND_STR
+{
+  mixin="org.nixos.idea.psi.impl.NixStringReferencingElementImpl"
+}
 antiquotation ::= DOLLAR LCURLY expr recover_antiquotation RCURLY { pin=1 }
 private recover_antiquotation ::= { recoverWhile=curly_recover }
 private string_part_recover ::= !(STR | IND_STR | DOLLAR | STRING_CLOSE | IND_STRING_CLOSE)

src/main/resources/META-INF/plugin.xml

@@ -37,6 +37,8 @@
                 id="org.nixos.idea.settings.NixIDEASettings"
                 instance="org.nixos.idea.settings.NixIDEASettings" />
 
+        <psi.referenceContributor language="Nix" implementation="org.nixos.idea.reference.NixReferenceContributor"/>
+
     </extensions>
 
 </idea-plugin>