feat(#13): missing-rho-reference lint

src/main/resources/org/eolang/lints/errors/missing-rho-reference.xsl

@@ -0,0 +1,77 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+ * SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+ * SPDX-License-Identifier: MIT
+-->
+<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:eo="https://www.eolang.org" id="missing-rho-reference" version="2.0">
+  <xsl:import href="/org/eolang/parser/_funcs.xsl"/>
+  <xsl:import href="/org/eolang/funcs/lineno.xsl"/>
+  <xsl:import href="/org/eolang/funcs/escape.xsl"/>
+  <xsl:import href="/org/eolang/funcs/defect-context.xsl"/>
+  <xsl:output encoding="UTF-8" method="xml"/>
+  <!--
+   Recursively check if owner object is not auto named object, otherwise check is attribute is present.
+   You can read more about auto named objects here: https://news.eolang.org/2025-02-21-auto-named-abstract-objects.html.
+   @todo #13:45min Restructure `report-missing` template and its call in the root template.
+    Currently, we are calling `report-missing` template from root template to do the job, while
+    we should return only the parent object to which the rho attribute refers. Also, don't forget
+    to rename the template to something like `rho-parent`.
+  -->
+  <xsl:template name="report-missing">
+    <xsl:param name="position"/>
+    <xsl:param name="attribute"/>
+    <xsl:param name="owner"/>
+    <xsl:choose>
+      <xsl:when test="$owner[not(eo:abstract(.))] or not(empty($owner/o[starts-with(@name, 'a🌵')]))">
+        <xsl:variable name="up" select="ancestor::node()[$position + 1]"/>
+        <xsl:if test="name($up) = 'o'">
+          <xsl:call-template name="report-missing">
+            <xsl:with-param name="position" select="$position + 1"/>
+            <xsl:with-param name="attribute" select="$attribute"/>
+            <xsl:with-param name="owner" select="$up"/>
+          </xsl:call-template>
+        </xsl:if>
+      </xsl:when>
+      <xsl:otherwise>
+        <!--
+          @todo #13:90min Enable processing of rho references inside auto named objects.
+           For now we ignore them, but we need to check them as well, as they are abstract
+           objects. Don't forget to add test packs with auto named objects.
+        -->
+        <xsl:if test="not($owner/o[@name=$attribute]) and not(contains($owner/@name, 'a🌵'))">
+          <xsl:element name="defect">
+            <xsl:variable name="line" select="eo:lineno(@line)"/>
+            <xsl:attribute name="line">
+              <xsl:value-of select="$line"/>
+            </xsl:attribute>
+            <xsl:if test="$line = '0'">
+              <xsl:attribute name="context">
+                <xsl:value-of select="eo:defect-context(.)"/>
+              </xsl:attribute>
+            </xsl:if>
+            <xsl:attribute name="severity">
+              <xsl:text>error</xsl:text>
+            </xsl:attribute>
+            <xsl:text>The rho reference </xsl:text>
+            <xsl:value-of select="eo:escape($attribute)"/>
+            <xsl:text> is missing in </xsl:text>
+            <xsl:value-of select="eo:escape($owner/@name)"/>
+            <xsl:text> object</xsl:text>
+          </xsl:element>
+        </xsl:if>
+      </xsl:otherwise>
+    </xsl:choose>
+  </xsl:template>
+  <xsl:template match="/">
+    <defects>
+      <xsl:for-each select="//o[@base and starts-with(@base, '$.^')]">
+        <xsl:variable name="position" select="(count(tokenize(@base, '\^')) - 1) * 2"/>
+        <xsl:call-template name="report-missing">
+          <xsl:with-param name="position" select="$position"/>
+          <xsl:with-param name="attribute" select="translate(translate(@base, '.^', ''), '$', '')"/>
+          <xsl:with-param name="owner" select="ancestor::node()[$position]"/>
+        </xsl:call-template>
+      </xsl:for-each>
+    </defects>
+  </xsl:template>
+</xsl:stylesheet>

src/main/resources/org/eolang/motives/errors/missing-rho-reference.md

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+# Missing `^.` Reference
+
+Each [rho][EO-specials] reference (`^.`) should point only to an existing
+objects.
+
+Incorrect:
+
+```eo
+# Foo.
+[] > foo
+  [] > message
+  [] > bar
+    ^.boom > @
+```
+
+Correct:
+
+```eo
+# Foo.
+[] > foo
+  [] > message
+  [] > bar
+    ^.message > @
+```
+
+[EO-specials]: https://news.eolang.org/2024-05-14-rho-sigma-delta-lambda.html

src/test/resources/org/eolang/lints/packs/single/missing-rho-reference/allows-rho-ref-to-present-object-from-deeply-nested.yaml

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+# SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/errors/missing-rho-reference.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  # Foo.
+  [] > foo
+    "yes" > message
+    [] > bar
+      while
+        [i] >>
+          if.
+            i.lt 5
+            QQ.io.stdout
+              ^.^.message
+            true
+        true > [i]

src/test/resources/org/eolang/lints/packs/single/missing-rho-reference/allows-rho-ref-to-present-object.yaml

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/errors/missing-rho-reference.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  # Foo.
+  [] > foo
+    [] > hello
+    [] > bar
+      ^.hello > @

src/test/resources/org/eolang/lints/packs/single/missing-rho-reference/allows-rho-ref-when-parent-has-multiple-objects.yaml

@@ -0,0 +1,14 @@
+# SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/errors/missing-rho-reference.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=0]
+input: |
+  # Foo.
+  [] > foo
+    [] > hello
+    [] > message
+    [] > bar
+      ^.message > @

src/test/resources/org/eolang/lints/packs/single/missing-rho-reference/catch-missing-rho-ref-from-deeply-nested.yaml

@@ -0,0 +1,22 @@
+# SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/errors/missing-rho-reference.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=1]
+  - /defects/defect[@line='10']
+  - /defects/defect[1][normalize-space()='The rho reference "messageeee" is missing in "foo" object']
+input: |
+  # Foo.
+  [] > foo
+    "yes" > message
+    [] > bar
+      while
+        [i] >>
+          if.
+            i.lt 5
+            QQ.io.stdout
+              ^.^.messageeee
+            true
+        true > [i]

src/test/resources/org/eolang/lints/packs/single/missing-rho-reference/catches-missing-rho-ref.yaml

@@ -0,0 +1,13 @@
+# SPDX-FileCopyrightText: Copyright (c) 2016-2025 Objectionary.com
+# SPDX-License-Identifier: MIT
+---
+sheets:
+  - /org/eolang/lints/errors/missing-rho-reference.xsl
+asserts:
+  - /defects[count(defect[@severity='error'])=1]
+  - /defects/defect[@line='4']
+input: |
+  # Foo.
+  [] > foo
+    [] > bar
+      ^.hello > @